-t s62s i The Mechanismof Formation of I2,3,4-Tetramethylnaphthalenefrom 2-Butyneand Triphenyltris( tetrahydrofuran ) chromium ( III )'

GeorgeiVI. lVhitesidesand William J. Ehmann: Contributionfrom the Department of Chemistrv, MassachusettsInstitute of Technology, Cambridge, lvlassachusetts 02139. ReceiuedJanuary 3i,, 1970

.\bstract: Reacrion of triphenyltris(tetrahydrofuran)chromium(III)(f) with 2-butyne y'ields,inter alia, 1,2,3,4' tetremerhylnaphthalene(2). A freeor metal-complexedtetramethylcyclobutadiene has beenexclr-rded as an inter- mediarern rhis reactionby the observationthat 1,2-dimethyl-3,4-di(methyl-rir)naphthalene(6) is not a product of I and 2-burlne- 1,1,1-d3 (3). Examinationof the relativeyields of 1,2,3,4,5-pentamethylnaphthalene(15) and 1,2,3,' .1.6-pentamerhylnaphthalene(16) tbrmed in reactionof 2-butyne with tri-o-tolyl-, tri'nr-tolyl-,and tri-p-tolyltris- (terrahldroiuren)chromium(III)demonstrates thiit a iong-livedaryne-chromium complexis also not an intermedi- atc in fhe:e cyclizations. Labeling and kinericisotope experiments using partially deuteratedderivatives of 1 fur- rhcr drsercdir bcnzynecomplexes as intermediatesin the tbrmation of 2. The reactionof trimesityltris(tetrahydro- iurrn)chronrrumtlll) with 2-butyneto torm cis-2-mesitylbut-2-enesuggests that an initial stepin thesereactions may be rnserrronot'2-butyne into a carbon-chromiumbond rvirh formation of an intermediatevinylic chromium reagent (2{r. The additional observationsthat 2-biphenylmagnesiumbromide and trichlorotris(tetrahydrofuran)chro- mrum(lll) relct to form 5-(2-biphenyl)dibenzchromole(29), and that this chromocyclcreacts with 2-butyneto yield 9.lr.t-dimcthylphenanrhrene,impliclte an analogouschromocycle 3,4-dimethyt-5-phenylbenzchromole (34) in the l'ormarronof 2. Taken togetheiwith further deuteriumexchange and labelingexperiments. thcse obscrvations lead ro rhc proposalthar the reactionof I with 2-buryneproceeds by initial insertionof one molcculeol'2-butyne into a phcnll-chromium bond of l, cyclizationof thc resultingvinylic chromium contpoundrvith elimination of benzene to iorm chromocycle34, ancireaction of the chromocyclewith a secondmolecule of 2-butyneto yield 2 (Scheme VII ).

rclooliuonrerizetionof acetyleneby transitionntetal butadienes'r0-r3 intermediates. or to proceedby a con- t t't3 clitllvsts prorides the basis for a number of certecl " n-ntulticenter" rcaction pat[. Of these useiulorslnic sl'ntheses.3Attenrpts to establishmech- suggestedand not necessarilyexclusive mechanistns, anisms ior this classof reactionshave been hindered only the nretallocyclicpathwxy has receivedpositire by' dif'hcultiesin identifyingthe activeorganometallic support.4'; Untbrtunately,without knowingeither thc catalvsts. Although a variety of structureshave been structuresoI the active catalysts.or, in most cases. postulatedtor these catalysts,it has proved possible evenelementary cietails of stoichionletry,reaction order. to isollte and characterizemechanistically significant or material balance,the designand interpretationof reectionintermcdiates or by-productsin only a small experimentsbearing on the rltech;,tnismsof these re- number oi reactions.{'; Precedcntsderived from the actionsremains a dillicultand subjectivematter. ertensirelv explored chemistry of transition-metalacety- Our interest in the mechanismof transition metal lenc conrplexessuggest that thesecyclooligomerization catalyzeclc.vclooligonrerization reections has promptc-d reactionsare initiatedby coordinationof one or more us to examine a related noncatalyticcyclization in- moleculesof acetylenicsubstrate to a metal atom or volvinga transitionmetal organometallic reagent: ui:.. metal atonr clusterof the catalyst.s'6 The process(es) the reaction of 2-butyne with triphenyltris(tetrahydro- b1'which the coordinatedacetylenes are subsequently furan)chromium(III) (l) to yield. inter alia, 1,2,3,-l- t t't:' tt conrerted to product has been variously suggested tetramethylnaphthalene(2;. This reaction is i-t to involre metallocyclic,r'z's ?r-allylic,s"'e'r0or cyclo- considerably more tractable subject for mechanistic examination than the catalytic cyclooligomerizations (l) Supportcdby thc National Institutcsot'Health, Grarrt No. GN{ - 160:0.by thc U. S.Army RescarchOtIice (Durham) Grant No. ARO-D- (8) For rclated proposals of mctrl-coordinittcd butadiene l,'l-dt I I - l l-1-G69l, and by Eli Lilly and Co. radicalsas reactionintcrnrcdiatcs, sec R. C. Cooksonand D. W. Jones. (l) Nattonll Sciencc FourrdatiorrTruince. 1965-1966; National Proc. Chem.'Soc., ll5 (1961); H' P. Throndscn'W. Metlesics'and H' Institutcsot' Hcalth PrccloctoralFellow. 1966-1969. Zeiss.-/. Organometal.Chem.,5, 176 ( 1966). (3) Rerrovs: (a) C. Hoogzandand W. Hiibcl in "Orglnic Svnthcscs (9) G. Wilkc,et al., Anqetv. Chem., tnr. Ed. Enql.,5,l5l (1966);A' T' via IIctaI Carbonyls,"L Wenderand P. Pino, Ed., Intcrscience,Ncrv Btomquistancl P. Il. \laitlis, J. Amer. Chen. Soc.,84, 2329(1961). York, N. \'., 1968.pp 3.{3ft'; (b) F. L. Bowdenand A. B. P. Lever, P. M. NIaitlis.et al.. ibid.,90,5l2l ( 1968). Orqunometal.Chem. Rec., Sccr. A,3,227 (1968); (c) E. Ochiai.Coord. (10) w. Schr.it'crancl H. Hcllm;rnn, '4nqerv.Chent.' Int. Ed. Enql'' 6, Citent.Rer'., J. -19( 1968); (d) J. P. Collmrn, Trattsitiort,lletal Chent., 518fl967). 2. | (1966t. (ll) H. Zcissin "OrglrtorrtctallicChemistrl'," H. Zciss,Ed., Amerr- (1) J. P. Collman.J, W.liang, W. F. Littlc,and i\I. F. Sullivarr,Inorg. canChcmical Socicty !{orrograph No. l{7, Rcinhold,Nerv York, N' Y ' Cltem.,7.l:9U ( 1968). 1960,pp 186fl (5) (a) O. S. llills and C. Robinsorr,Proc. Chen..Soc., 187 (196'l); (lli w. Hcrrvig,W. \Ictlcsics,and H' Zciss,J. Amer. Chem.Soc'. (b) R. P. Dodge and V. Schomaker,J. Organontetal.Chen., 3' :7'l 81.610l ( l9-59). (1965); (c)J. F. Blount,L. F. Dahl, C. Hoogzand,and W. Hiibcl, (13) G. N. Schrauzer,P. Glockner,and S. Eichtcr,Angew. Cherrt" J. Arner.Chem. Soc.,88,292(1966); J. T. lv{ague.ibid.,9l.198l (1969); Inr. Etl. Engl..3, 185 (196'1);G. N. Schr.tuzerrnd S. Eichler,Chettt' L. R. Bateman,P. M. Maitlis,and L. F. Dahl, ibid.,91,7292(1969). 8er..95.550( 196:). (6) W. Hijbcl, "Organic Synthesesvia Metal Carbon.'-ls."I. Wender (l-l) Rclatcclreactions have becp obscrycdwith diphenylnicket[\l. and P. Pino, Ed., Intt-'rscicrrce,Ncrv York, N. Y., 1968,p i73 ti. Tsutsui arrd H. Zciss,./. .{nter. Chenr.Sr-lc., El, 6090 (1959)land rvrtlr (7) L. S. IWerirvether,!1. F. Leto, E. C. Colthup,ancl G. W. Kcn- cycloperrtl{icnylmethylirortdicarborrl [ ;.rrtd c;-clopcltadiepylcthrt- nerly, Org. Chenr.,27. 3930( 1962); W. Keim, J. OrguncmetalChem., molybdcnum tricarbonyl [A. N.ku'rur.r .rrrd N. H.giharit, i\'lipp,trt "/. ( 16.l9 I ( 1969);E.-A. Rcinsch,Theor. Cltenr. .1cra, ll, 196( 1968). Kag'rt k tt Zos s lt i, 8.1.3'l'l ( I 961) ; Che nt. .1b s r r, 59' i'i0l I d 1963)l'

LVlr i ra sidcs, Elrrnun n 5626

for severalreasons. First, the composition and struc- version of 3 ro retramethylnaphthalene-d6by way of ture of the starting organometallicreagent I are rea- r-allylic or metall,rcl'clicintermediates, represented sonablywell defined.rr'r2'rs Second,the fact that con- version of a o-bonded phenylchromium moiety into H | ( tl " \-,/'" L ft. tetramethylnaphthalenenecessarily involves the cleavage 3-'lrPh, of an ortho carbon-hydrogen bond providesan opportu- ^,-'-\ -r, Lrt ( n nity to apply a number of standard mechanistictests to {a those stepsof the reaction in which the carbon-hydro- gen bond is broken and the corresponding carbon- H I I t) ^-hr carbon bond formed. Finally, since the organochro- \'- ! r rit 6

mium reagent is directly involved as a reagent, and Hlll \\\ CH since it is not regenerated,there is no ambiguity con- 9H, {b I cerning the nature of the "active" organometallicspecies C in the reaction. Nonetheless,despite the obvious differ- llr r_-l ences between this noncatalytic cyclization and the U ilt V. CDt catalytic cyclooligomerization reactions,there are also I r.'._ph CD, I parallels suggest ,r^\'_ enough to that information concerning 3 the mechanismo[ the former should be pertinent to a:) QD, mechanisticquestions concerning the latter. JA r--lJ r'. / Resultsand Discussion D \.r'\ nt l\lechanismsInvolving a CyclobutadieneIntermediate. \.,' 1i'-rn The initial objectiveof this study was to determineif Dr'- \ either tetramethylcyclobutadieneor a chromium- r'H 'l tetramethylcyclobutadienecomplex were an interme- JO diate in the conversionof 1 to 2. Previousdeuterium- (-H Dr'. / labeling studiesof the cyclotrimerizationof 2-butyne \,zz\ to hexamethylbenzeneby an organochromiumcom- i .t-r'-Ph ..S-,/ tr -/ \ pound of unknown composition derived from I had rlr \ t'D CH, demonstratedthat a chromium-tetramethylcyclobuta- I dienecomplex wasnot an intermediatein the reaction.16 JC Although it seemedprobzrble that the same resultwould schematicallyby Sa-c. or by way of any other "linear" be found for the noncatalyticconversion of I into 2. cyclooligomerizarionpathway that does not allow thc the fact that these earlier labeling studiest6 had es- four methyl groups derivedfrom the two reactingmole- tablishedthat the mechanismof catalyticcyclotrimeriza- culesof 3 to becomeequivalent, will lead to 6,7,8, tion varied with the catalyst indicated that it would and 9 in relativeyields of 0/":50/":25ft:25f.t. be prudentto treatthis point explicitly. Thus, a clear distinction betweenthe mechanistical- The sameexperimental probe usedto testthe catalytic ternativesunder considcrationcan be made on thc cyclotrimerizationsof 2-butyne-l,l,l-& (31 to hexa- basisof the relativeyield of 6 formed in the mixturc nrethyl be nzene-d for i ntermed iates of tetramethylcyclo- s of deuteratedtetramethvlnaphthalene isomers: the ob- butadiene-likesymmetry with served, somemodification, servation that 1.2-dimerhyl-3,4-di(methyl-d)naphtha- to excludethis type of intermediatein the conversion lene (6) is not a product of reactionof 3 with 1 is sufli- of 3 to tetramethylnaphthalene-d5.This experimental cient evidence to excludc a free or complexed tetra- testis based on the supposition that the four ring carbon- methylcyclobutadieneas a reactionintermediate. carbon bonds of free or metal-complexed tetramethyl- The relative yield of 6 in the mixture of tetramethyl- cyclobutadieneare chemicallyequivalent.tT With this naphthalenes6, 7,8, and 9 obtained by reactionof I supposition,reaction of 1 with 3 taking place by way and 3 was establishedusing a chemical degradation of an intermediate of cyclobutadiene-like symmetry designedto capitalizeon the fact that only 6 contains would lead first, with equal probabilities, to inter- adjacentlabeled methyl groups at the I and 2 positions mediatescontaining the head-to-headand head-to-tail of the naphthalene ring (Scheme I). Oxidation ot' tetramethvlcyclobutadiene-domoieties representedby the mixture of isotopically labeled tetramethylnaph- 4a and 4b, and ultimately by a pathway whose precise thalenes with trifluoroperaceticacid and boron tri- nrechanismneed not be specified to the four isotopically fluoride etherateyields a mixture of the labeledketones substituted tetramethylnaphthalenes 6. 7, 8. and 9 10, 11, and 12.le Ozonolysiso[ this mixture without in relative yields 25%:50f:12.5fl:12.5/,.1s Con- separation into individual components, followed b1' (15) For a crysralstructurc of the relatedcompound p-CHrCeHr- catalytic reduction of the resulting ozonides, yields CrCl:.3THF, seeJ. J. Daty, R. P. A. Sneedcn,and H. H. Zeiss,J. Amer. 13, products. Chem.Soc., 88..1287 (1966). among other Cleavageof 13 with aque- ( l6) G. \{. Whitcsirlesrtnd W. J. Ehmann,ihkl.,9l.1800 (1969). ous sodium hydroxide yields methyl isopropyl ketonc (17) R. P. Dodgc and V. Schomaker,Acta Cr)'srallogr.,18, 6l,t (14) and sodium 2-acetylbenzoerte.:') (196-s);J. D. Dunirz, H. C. NIcz,O. S. ivlills,and H. M. tv[.Shearer, Halc. Chirn.,lcra,45,617(1962); C. S. Yarrnoni,G. P. Ceasar,and (19) H. Hart and R. I(. Murray, J. Org. Chem.,32,2448 (1967). B. P, Daile."",J. Aner. Chent.Soc., 89, 2833 (1967); H. Obcrhammcr (20) For similar base-catalyzedclcavagc reactions of substituted aud H. A. Brune, Z. ,\'aturfbrsch.,24ar607(1969). p-diketones,see R. G. Pearsonand E. A. Mayerle,J, Amer. Chem.Soc.. (18) Wc assumeas previously'dthat any dcuteriumkinetic isotope 73,926 (1951). Although the cleavageof l3 might a priori havepro- etlccts in thc formarion of the deutcratcd tetramcthylnaphthalene ceededby scissionof the carbon-carbonbond adjacentto that broken isomcrs6-9 are negligiblc,and thar the relativeyields of thcscisomers in Scheme I, yielding sodium acetateand 2'-acetyl-2-methylpropio- expcctedl'rorn cach ot'thc reaction paths considcredcan bc calculated phenone,only the mode of cleavagcindicated in this schemewas ob- cntirclvt'rorn statisticu I considerations. served.

' Jourrutl ol tlrc .4rn(rican Chentical Societ.v' 92.l9 I September23, 1970 5627 SchemeI. Degradationof 1,2,3,4:Tetramethylnaphthalene-do In order to be certain that scramblingof the deu- terium label present in 6 does not take place during ('F-.....-...-...... * ('o ll this degradation, an authentic sample of 6-was syn- Bl.' ()i.t thesized,using the sequenceof Scheme II, and de- graded; mass spectroscopicanalysis of the resulting methyl isopropyl ketones yielded the distribution of o deuterium label summarizedin Table I. The observa- tion that no detectableyield of l4-d,t results from the degradationof authentic1,2-dimethyl-3,4-di(methyl-d3)- ofr+of' naphthalene(6) establishesthat no scramblingof methyl 1.Ot groups or of deuterium atoms occurs during degrada- l0 ll g.H,, Pa,t tion, and indicatesthat the analyticalscheme outlined -.> o in SchemeI should be capableof detectingany signifi- cant concentrationof 6 admixedwith 7. 8. and 9.22 Degradation of the mixture of tetramethylnaphtha- lene-dr isomers obtained by reaction of triphenyltris- (tetrahydrofuran)chromium(III)with 2-butyne-l,l,l-ds, followed by mass spectrometricanalysis of the resulting 14,yielded results also listed in TableI. Thesenumbers o o gF',-Co:\:'l Table I. NormalizedCalculated and Observedlsotopic N;tOH Compositions(7)',b + ll,o o Tetramethyinap htha lene tl source l4-,/o l4relt l+d6 cr 6 58.2 0.5 41.2 n) Reaction of 1 and 3 0.0 99.8 0.2 l4 Calcd: cyclobutadiene t2.5 75.0 12.5 This sequenceof reactionsisolates adjacent methyl Calcd: "linear" 0.0 100.0 0.0 groups from the I and 2 positionsof tetramethylnaph- o Corrected for CDrC:CCDr and CD.:HC:CCHr present as th.rlenein the isopropyl group of 14. The reaction impurities in the starting CDtC:CCH'. b The estimatedprecision conditions for the cleavage13 -* 14 were specifically in thesenumbers is ,-=t I 73. adrustedso that any deuterium presentin the methyl group directl.v-bonded to the carbonyl moiety in 14 arenormalized and havebeen corrected for contributions *'as *'ashed out during the course of the reaction.2r to the mass spectra arising fionr naturally abundant Consequently',the methyl isopropyl ketone obtained r3Cand from the 2-butyne-dqand 2-butyne-1,1-dpres- by ciegradationof 7, 8, or 9 using this sequenceshould ent as impurities in the 3: that is, they represent be entirell' ll-d3, while that obtained from 6 should the yields that would be observedfor reactionsof tri- be a I : I mixture of l4-dt and l4-do.te Thus mass phenylchromiumwith pure 3. For comparison,Ta- srectroscopicanalysis of the deuterium distribution ble I also containsthe relativeabundances of the iso- in the methll isopropylketone obtained from degrada- topically substitutedderivatives of 14, calculatedon rit-rnoi the mixture of labeled tetramethylnaphthalene- the assumptionthat the reiiction proceedsentirely by d; isomers isolated from reaction of 1 and 3 can be way of a cyclobutadieneintermediate (4) and those sinrpll'related to the relativeyield of 6 in this mixture. calculatedon the assumptionof a noncyclobutadiene SchemeII. Sl nthesis of processinvolving only intermediatesof the type rep- I .l- D rmetht'l- l,.l-di( methyl-dr)naphthalene6 resented schematicallyby 5 (called "linear" in this COCH table). an r-H I. LiAll), Within the limits of detection of this procedure l. I'flr', -> (tL%) no l4-do or l4-dewas obtainedfrom this deg- 3. Lir\ l [), radation. Hence, no 6 was present in the starting mixture of tetramethylnaphthalene-doisomers. This CD, observation establishesthat neither tetramethylcyclo- 1 (cll-()),'llcl' HOAc cD, any intermediateof similareffective 2.I,i.\IH, butadienenor other symmetryis involvedin the conversionof 1 to 2. NlechanismsInvolving a Benzynelntermediate. Zeiss CD, and Sneedenhave advancedthe proposal that conver- /-n L rCH,OI", (1) LUJ sion of triphenyltris(tetrahydrofuran)chromium l{ct. H0,\c (2) takesplace by a mecha- + to tetramethylnaphthalene ?.LiAIH. nism involving an intermediate benzyne-chromiunr CH, ct{r CH, (22) The observation that the normalizcd abuttdance from authentic 6 6 of l4-do is -20% higher than that of l490% dr material W. lvl. Schubcrt and P. H. LeFevrc, J. Amer. Chem.,Soc., 9l' 7716 by massspectroscopic analysis. ( 1969).

lVhitesidas,Ehmann,' 1,2.3,1-Tetrumethvlnaphthalene 5628

complex. derived from penramethl'rnaphthalenes elimination of a chromium TablerI. Yieldsoi from Reactionof hydride fragment from 1.23 This proposal finds little Tritolylchromrum(tllI Reagentswith 2-Butyne support in the availableliterature dealingwith benzyne -Yield,3"- chemistry.:{ Although a complex of benzyne with R,Cr.-lTHF r5 t6 silver(I)has beenimplicated as a transitory intermediate (aTohltrCr in the thermal decomposition ITHF 60 0.0b of benzenidiuzonium-2- (m-Tolrlr:CrITHF 5.1 carboxylatein the presence 47 of silver ion25and a stable (p-TolrltrC;ITHF 0.06 69 complex of a fliorinated cyclohexynederivative with " Yields are basec urfl ti.lca::umprion that formation cobalt has been prepared,:6 extensive efforts of I equrr to of pentamerhlInapnrheie;:e pcr equivalent of triarylchromiurrr synthesize authentic benzyne-transition metal com- reagentwoulJ consl;rutc3 ItlO'" .vield. Reactions were carncd plexes out in THF 5 have been unsuccessful.2i,27,2sNevertheless, solurr,.rn.tt 15, Less than 0.5 ft could have bccrr detected. tetramethylnaphthalene rs formaily derived from the elementsof one moleculeof benzyneand two molecules of 2-butyne; further, chromium compoundsin various plexes shouid pre'rrldr'a pathway for interconversion valencestates have been implicated is hydrogen atom of o-) m-. and l groups (Scheme or hydride ion acceptorsin the Etard reactionrn.and i-ierll III). The in other reactions of organochromium reagents.:3,rebSchemeIII. Forn-rr:.onoi penrrmethylnaphthalenes Thus, mechanismsfor formation of 2 relatel to that representedby eq l, although improbable. cannot .,/ be disregardedarbitrarily. V;-r'- /- \ t^' ,,rfrr}t (( H r-- H.', + .l , \ \:/ /, x { x X / .r:. \

(Q|" l'(-)tc'I CH, nr.

we have carried o't severalexperiments designed an,a-a.U\ Cll C-CCtl to excludecertain classesof mechanismstor the ion- version of l to 2 requiring benzyne intermediates. These experimentsdo not prov'ide sufficientevidence CHr to excludea// possiblenrechanisms for I -. 2 involvins benzyneintermediates, and additionarexperiments thel CH' oreticallycapable of excluding the remainingclasses CH ('H of mechanismsdo not seemto- u. practicalii the re- CH, l5 action systenrunder study. Nevertheless,the observa- l5 tions reported here. together with evidence contained observationrhat reactionol'2-buryne with tri-p-tolyl- in the following section.combine effectivelv to exclude chromium yields no 15. and that reactionwith tri-r.r- benzynepathways for tornrationof 2. tolylchronrium yields no 16. demonstratesthat the stereochernicaler idenceagainst rer.ersible elimination tolylchromium reagcnrsdo ttot equilibrateunder these of a chromium hydride moiety during the reactionof reactionconditions. Hower er. isomerizationof, e.g., triarylchromiumreagents with acetylenes was obtained o- to z-tolylchronrium br way of an intermediate by the yields of 1.2.3,4,5-pentamethyl- _examining dehydrotoluene-chromiumcomple,x would requirethat naphthalene(15) and 1.2,J.4.6-penramerhylnaphthalene the lifetime of this inrermediatebe sufficientto permit (16) formed in reactionof tri-o-tolyl-, tri-rn-tolyl-,ancl the torsionaround the aryne-chromiumbond necessary tri-p-tolyltri s(tetrahyd rofura n)ch romiu rn( I I t; wiih 2-bu- to transferthe hydrideligand from its coordinationsite t.v.'ne(Table II). Equilibration of these tritolylchro- on the metal to the carbon atom originallybonded to nriumconr po Ll nds with dehydrotoluene-chronrium com- the metal. Thus, reversiblechromium hydride elimi- nation from thesetritolylchromium (13) (a) H. H. p. reagentscould be Zciss.rrd R. A. Snccclcrr,,lnge*,. Cltent., Ittt. Erl. Ettql..6,43-5(1967); (b) reconciledwith the data of Table provided R. P. A. Srrccdcnand H. H. Zciss.-/. Organo- II, that the ntetal.Chent.,20. 153( 1969). rate of collapse of the dehl,drotoluenecomplex to (2-l) Sur'c-v' R. w, Horrrrra.rr. "Deh."-cirobc.zcnc anci cl,croar- o-tolylchromium reagent was nruch more rapid than klrrcs." Acadcrrric Prr-.ss.Ncrv york, N. y.. 1967. (:-() L. Fricdrrurn,J...1 rrrer. Cltent. Soc., g9. 3071(.1g67). the rate of torsion around the arvne-chromiumboncl. (16) R. L. Hurt arrt[ c. wilki.so., Irtorq. Crtent.,4, l27o il965); There is presentlyno way oi estimatingthe barrier to N' A. Builcy, l\1. R. Churchilr, R. Hu't, R. Nlason,anci G. wilkinsou, this Proc. Chenr. Soc., .10I ( 196-l). type of torsional motion in the hypothetical (:7) Wirrig G. .ud F. Bickclhaupr,Chent. Ber.,9l, Sgl (195g): H. benzyne-chromiumcomplexes. although a priori torsion Hcllrrrarrrrarrcl C. lVI. Scltcl,tr, ,lttrt. Chenr., 642,21 (1961); H. J. S. of a benzynein an octahedralcomplex might be ex- \\'irrklcrrnd C. \!itrig, J. Ors, Cltem.,2g, l73j ( 1963). (ls) A pectedto be more rapid than that observedfor corrrlror.d strggcsrecito be . bc.zyrrc-.ickcl complcx has ethylene bccrr rcportccl, but cl itir-'rrcecontirmirrg its structure has not appearecl: in square planar rhodiumr0or platinumrr complexes. c/'., E._W. Gowli.C, S. F. A. I(ctttc, a.cl C. iVI. Sharples, Che'm.Com- trrtrtt.,2t(1968). (30) R. Cramer,J. B. I(line, and J. D. Roberts.J. Amer. Chem. Soc., (19) (a) f(' B. wibcrg r.cl R. Eiscrrhar, Tetartecrron,20, ll5l (196.r); 9r,25190969). I. Nccsoiu, v. Przcrrrcrchi. A. Ghenciulcscu, c. N. Rcnrga, aud c. D. (31) A. R. Brausc,F. I(aplan,and tvt.Orchin, ibid.,g9,266l (1967): Ncrritzcscu,ibil.. 22.3017 (b) t 1966): G. Henrici-Olive rnci S. Otive, C. E. Holloway, G. Hullcy',B, F. C. Johnson,and J. Or.gtrrtontctql. J. Lewis.J. Chem. Chcttr., 9, 325 (1967). Soc.A,53 (1969).

Journul of thc.lrttariutrt Clrcnticul Sttciety,I 92 I9 I Septentber2i, lg70 5629 Thus, the data oI Table Il.indicate qualitativelythat of the four possiblelabeled triphenylchromium com- the conversion of tritolyl- and presumably other pounds obtained in this reactionis that expectedfrorn triarylchromium reagents to the corresponding tetra- statisticalconsiderations: l8a:18b:f 8c:18{ I:3:3: I. methylnaphthalenesdoes not involve reversiblefor- Clearly, in this mixture, only l8b and l8c offer the mation of a long-lived aryne-chromium intermediate, possibility of an intramolecular choice of deuterated but they do not permit a rigorousestimate of the lower and nondeuteratedphenyl groups during the step in limit for the lifetime of a benzyne-metalintermediate which the reaction sequenceresulting in conversion w'hich would be compatible with the absenceof ob- of a particular phenyl group to tetramethylnaphthalenc ser!'ablepositionel isomerization during the reaction. is initiated. However, these compounds constitute Two comolimentar,v-deuterium kinetic isotope effect the majority of the mixture, and the presenceof 18a and messurementsrelate to the possible intermediacy of l8d does nothing to obscurethe conclusionthat there metal-con:plexedbenzyne as a transitory intermediate is no isotope effect on the reaction in which phenyl in the conrersion oi t to 2. First, the isotopeeffect group selectiontakes place. on the rete of cleerageof the carbon-hydrogenbond Control experiments establishedthat the relative oi the phenrl ring incorporatedinto the tetramethyl- yieids of tetramethylnaphthalene-doand -dt were nr:hrhrlene \rf,s determined to be ktlko : 2.7 * independentof the extent of conversionof the mixture 0.I r: b1 n'l:tss spectrometric determination of the of compounds 18a-d to products. Thus, the absolute rrir,,r r'rr tetremerhllnaphthalene-dt to tetramethyl- ratesof formation of thesecompounds, and by inference nrrnrnrl:::e-d iormed during reactionof tri(phenyl-2- the absoluterates of reactionof l8b and 18c, are equal d:)t;rs(telrrhldrr-'riurrn)chromium(III)(17) with 2-bu- throughoutthe courseof the reaction. ti:i. Se:.rn..:.the isotope effect characterizing the These kinetic isotope effect data lead immediately, to one important conclusionconcerning the mechanism of conversion of 1 to 2. The moderateisotope effect , i{ r'-t'('l{ , observedin the reactionof 17 with 2-butyneestablishcs that a carbon-hydrogenbond is brokenin the reactiorl that determineswhich of the two geometricallyequiv- alent carbon atoms originally ortlto to the chromiunr D CH, atom is to fornr a ring juncture in the tetramethy'l- /TLI LIrj naphthaleneproduct. This same rerction, regardless of its precisenature, obviously occurs during conversion oi l8b and 18c to products. However,the negligible H CH, H CH, kinetic isotope effect observed in the latter reaction :.7 t 0.1 1.0 indicatesthat the reaction that determineswhich of the three phcnyl rings of I is ultimatelyconverted to a phenl'l group from among undeuterated sr'i.i:1.'r:'l'.1 2 does rrot involve carbon-hydrogenbond breaking, phenyl groups bondedto chromium ::.; :erdeut:reted since the isotope effectfor the reactioninvolving com- \r-rs be k^lko : 0.97 * 0.02(or 0.99per 3s:.rolisheCto petition betweencorresponding C-H and C-D bonds ,.',,:i:', bond) by mass spectrometric crrbon-hldrogen in differentphenyl groups should be the same as that -J\.i:i:it.ltlr)n ratio of tetramethylnaphthalene-r/o of the chnracterizingthe competitionbetween C-H and C-D : -r lr'r:rx'rirthrlnaphthalene'dr formed on reaction of bonds in the same phenyl -sroLrp.Clearly the phenyl rrrih mixture of organochromiumcom- l-::i;::': the group cannot be selectedin a reaction taking place on treatmentof chromium trichloride Itr:iiS obteined after the C-H bond is broken. Thus, the phenyl ring ur::l of phenylmagnesiumbromide and e l:l mixture incorporated into tetramethvlnaphthaleneis selected bromide. The relative yields f r:':1\l-rl;-magnesiunr in a reactionwhich takes placeheJ'ore the ortho carbon- {,'^H.}tgBr + CeDrillgBr hydrogenbond is broken. l:I Further interpretationof theseisotope effects in terms r of specificmechanisms involving benzyneintermediates Jc.cr,rtn is complicated by ignoranceof the geometry of 1: ii ,':' 'C.,[{.r,(C.D,)Cr+ rCnH,XC^D;).rCr + (CeDr),Cr both meridional(1a) or J-acial(ltr) arrangementsof the lEa l8b l8c l8d phenyl groups of this compound are conceivable. There is no experimentalevidence available that bears Jcu,c-r-'cH, directly on the geometryof l: however,the meridionul isomer seems the more probable of the two possi- CH. D bilities.r3 On the hypothesisthat the observedisotope CH, D CH, pl. I lr Tr r r I,II r t flf THtr t/ t/ 1,2"" CH, Tttr Ph-('r-'l'Hl" t,l]-L H CH, D CH, ,/l THF/,!, DI.. I 1.00 1.03t 0,02 rl) I fl F la lb (l:) It is possible(ckte infra) that the rate of the reactionwhich is the rev'crseof thc step in which thc hydrogen is removed from the phenyl group is competitivervith thc subsequentsteps of the conversionof l7 (31) Dichloro(p-tolyl)tris(tetrahydrofuran)chromiumexists ln a LI or l8 to products. Hencc, rhe observedratio o[2-dr to 2'doproduced in meridionalcontiguration; bis(trimcrhylarnine)trichlorochromium(III) the reaction of 17 should bc considcredto yield a lower limit for the is a trigonalbipyramid.rr kinctic isotopc cilect dcscribing the breaking of the carbon-hydrogen (3-1)G. W. A. Forvlcs,P. T. Grecnc,artd J. S. Wood, Chem' Com' bortd. rnurr.,97l(1967).

lVltitcsidas,Eltrnunn l.).i.1-Tarrunteth.vlnaplttlrulena 5630 effects arise during chromium hydride elimination, unique pheny-l group of either the starting organd any mechanism that cortverts one of two (or three) chromium reagentor an organochromiumintermediate geometrically eqrioalenr phenyl groups to benzyne, such as 21 or 2l *ould be compatiblewith the isotope regardlessof the nature of its rate-determining step, effectdata. procidedthat this extrusiontook placeafter can be rigorously excluded on the grounds that it the rate-limitingstep for the overallreaction.ss should give rise to similar isotope effectsin reactionsof NlechanismsInvolving a NletallocyclicIntermediate. 17 and 18. On the other hand. mechanismswhich The first substantralclues concerning the mechanism involve conversion of a geometrically unique phenyl of conversionoi I to I lay among the other products group to benzyne require further consideration,since formed in this rerlcrion(eq 2). Triarylchromium(III) at the most elementary level of interpretation, mech- compounds rearrrnse thermally in the absence of anisms of this type would be compatible with the stabilizingiigands to e complex mixture of aromatic conclusion (uide supra) that the selection of the phenyl hydrocarbons ani benzene-and biphenylchromium(l) ring converted to tetramethylnaphthalenemust precede 7r-arenecompler:s:i6 thus, the presenceof these breaking of carbon-hydrogen bond of this ring. compounds in the rerctrL)nmi.\ture is of no assistance Thus, for example, the isotope effect data are in- in deducing a mechanism for the reaction. Hexa- compatible with mechanisms requiring extrusion of methylbenzeneis :roduced in significantquantities only benzyne from one of the circled phenyl groups of /-\ complexes19 and 20, regardlessof the position of the t/-\ \ - r" , 1:'. r rate-limiting step for the reaction; their compatibility with mechanismsinvolving elimination of the indicated \\-r-r I er1ulr phenyl group of 21, in which the phenyl group con- verted to benzyne is unique by virtue of its relation I phenyl groups, Z\\//*/ to the two remaining or from 22, in ttl +O+ffi. which it is unique by virtue of its relation to the co- \--\Z'. ordinated acetylenicligands,3s depends on the position > I ; 0.1-0.2 of the rate-determining step. If benzyne formation ,,r-l. from complexes 21 or 22 were rate limiting, tetra- i methylnaphthalene-r/,rshould be formed more rapidly than tetramethylnaphthalene-dt in the early stagesof the [-Yr + r-arenechromium rlt \-/ \_ reactionof 2-butyne with the mixture of compounds complexes 18a-d, because the kinetic isotope effect observed Hi 23 / rll. \ (ili) -,, - -().05 \j,7 THF \// t nf l,/ l,/ (PtrFt'r-THF Ph-('r-THF -6;( when 2-butyne is presentin large excess,rr'r2and is ,rr/),'I'Ir'I | probably formed in a processunrelated to the con- q9 \j/ THF versionof 1 to 2. On the other hand,the observation l9 20 of small quantities of cis-2-phenylbut-2-enein the pl, ^,\. product ^," l'n mixture after hy'drolysissuggests that insertion THF \ l,/ l,/'\ of 2-butyne into a carbon-chromium bond of t or (l'h|_'u, Cr'-THI" (Phf-{ir-THF some related organochromiumcompound may be itn ,/ | v,/l sT rrrr Ph'l_ initial step in conversion oI I to products. This Ph suppositionis strengthenedby the relatedobservatiott, 2t 22 first reported by Zeissand confirmedin our work, that for reaction of 17 with 2-butyne would influencethe reactionof trimesityltris(tetrahyd rotbran)chromium( I I I ) relative rates of formation of benzyne-ds and -d+. Ph THF Ph THF If, on the other hand, benzyne were formed in an l,l t l,/ equilibrium established before the rate-determining I * Ph-Cr-/l Ph-Cr step, some combination of a (presumably) small ,/l ,/l / .rr"/,,A--Ph-l equilibrium isotope effect and a subsequentkinetic THF Ph ^"^ CH, isotopeeffect involving, €.9.,cleavage of a chromium- CH, (or hydride deuteride) bond, would be responsiblefor 24 overall isotope effect observed for 17. This com- bination would again ensure that tetramethylnaph- with 2-butyne, followed by hydrolysis, yields cis-2- rs thalene-dgwas formed more rapidly than tetramethyl- mesitylbut-2-enein high )'ield. Normal cyclization naphthalene-dtin the early stagesof reactionof 18a-d. of the type which would lead to a product analogousto The observation that the ratio of tetramethylnaph- tetramethylnaphthaleneis, of course, suppressedin thalene-r/oto -clt remains constant throughout the this reaction by the substitutionof methyl groups for reactionexcludes both of thesepossibilities. hydrogen atoms in the positionsortho to the carbon- Howev'er, a mechanism for conversion of 1 to Z chromium bond, although an "abnormal" cyclization requiring extrusion of benzyne from a geometrically yielding 2,3,4,6-tetramethylindene(26) is observed. (15) Hiihlc and Stolzchave shown thar one moleculeof THF is lost selecrivelyfrom CrPhr.3THF to yield CrPhr'2THF. If a reactionof (36) M. Tsuisuiand H. Zeiss,./.Amer. Chem.Soc., 81, 1367(1959); this sort occursin THF solution, a moleculeof 2-butynecould complex J. Hiihleand G. Stolze,J. Organomeral.Chem.,8,3ll (t967). with the CrPhr. 2TH F in a manner that rvould "selcct" the phenyl (37) R. F. Heck, Adcqn.Chem. Ser., No. 49,l8l (1965). group to be involvetl in the subsequentcyclizatiorr. J. Hihle and G. (38) W. Metlesicsand H. Zciss,../.Amer. Chem. Soc., El' '1117 Stolze,Z. ),lutur1brslr..l9b, l08l (1964). (l9se).

Journul oJ tlrc.lmaricurt Clrcnticul Society t' 92:19 I September23, 1970 563I

/ compounds to be discussedbelow, it is presumed that _\A / the label is localizedin the ortho positions. In testing the hypothesis that the first intermediate \ri formed in the conversionof 1 and 2 is a styryldhromium 24, it was important to have independent 25 compound 70% information concerning the reactivity of organochro- / A \ rg{,c-(-o{r (< + mium compounds of this type toward 2-butyne. \1/r )Fr,' Clearly, if reaction of an authentic styrylchromium J compound with 2-butyne leads to a spectrum of JL/ products similar to that obtained from 1, the case *(A for an intermediate styrychromium reagent in the latter 26 reaction is strengthened. In initial experiments, the 20% products of reaction of the organometalliccompound derived from trichlorotris(tetrahydrofuran)chromium- 23 In order to confirm that the substituted styrenes (III) and 2,2-diphenylethenylmagnesiumbromide (27) styryl- and 25 are in fact derived from the analogous with 2-butyne were examined.{0 The styrylchromium chromium compounds by hydrolysis, the extent of deuterium incorporation into these compounds fol- () lowing treatment of the reaction mixtures obtained r front 2-butyne and triphenyl- or trimesityltris(tetra- ;,r.;rHF'rHF-OY hydrofuran)chromium with deuterium oxide was ex- \_/-) .i that (.il('-{.(.t, amined. Mass spectrometricanalysis established Ilg Br >< the isotopic composition of 25 isolated under these 27 28 conditionswas L7o dr, 51% d1,ond 15% d6, and was 12% consistent with initial insertion of 2-butyne into the compound which is presumed to be an intermediate carbon-chromium bond of trimesitylchromium to in theseconversions does react with 2-butyne to form yielcl an intermediate styrylchromium reagent. Mass a cyclic aromatic product analogousto 2: however, spectrometric analysis of 23 obtained following a the yield of this product is significantlylower than the deuteriumoxide quenchof partiallyreacted I revealed yield of 2 obtained by reaction of triphenylchromiunl- a more complicatedtabeling pattern: ci;., a mixture (lll) with 2-butyne. Whether this differencein yield of do,d1, cod, surprising|y,d, specieswere present. The is mechanisticallysignificant is unclear. Since styryl- position of the deuteriumin theseisomers was localized chromium reagents appear to be thermally much by oxidizing the 23 to a mixture of isotopically sub- less stable than l, their rapid the-rmal conversion stituted benzoic-do and -dt (44%) acid with 66%) to the correspondingbutadiene dimers may be more potassium permanganate. On the assumptionsthat facile than in the caseof the organochromium reagent, deuterium was presentin the side chain of the labeled 24, in which only one labile styryl moiety is bonded to 23 only at the vinylic position as was indicatedby the eachchromium atom. nnlr spectrum, and that no deuterium was washed ln an etl'ort to circumvent some of the ambiguities out of the ring during permanganateoxidation, com- originatingin the thermal instabilityof the styrylchro- parison of the isotopic conrpositionof the 23 before mium reagents.the preparertionoI tris(2-biphenyl)- cleavagewith permanganatewith that of the benzoic tris(tetrahydrofuran)chromium(lll) was attempted. acid isolatedalter cleavageindicated that the deuterated Our interest in this compound as a potential model 2-phenylbut-2-enewas composed of a mixture of for 24 rested on two considerations: first, since thc four isomers (23a-d). Of these isomers, 23b is the chromium atom of this substancewould be directly compound expected from hydrolysis of the styryl- bonded to an aromatic carbon atom. its constituent chromium compound which would be formed as a carbon-chromium a bonds might be expectedto have product oi insertion of 2-butyneinto a carbon-chro- reasonablethermal stability: and second,the geometry nrium bond ol 1. and 23a might be formed by decom- of the carbon-chromium bond of this material with position oi the st1'rylchromiumby some pathway respectto the o-phenyl group oi the biphenyl moiety' thut woui.l involvc transfer of a hydrogen to the would be expectedto resembleclosely that character- izing the styrylchromiumreagent 2{. Treatment of 2-biphenylmagnesiumbromide with qto,t%% trichlorotris(tetrahydrofuran)chrorniurn(III),followed by reactionof the resultingorganochromium compound 23b 23c 23d did. in fact, yield 9.10-dimethylphenan- ,'1.)' \ with 2-butyne. (,)'l7-, t { 'J-),' r l r l2ii threne(30) in 80% yield basedon chromium.{t Thus. the reactionsleading to cyclizationand aromatization position.3e The ring-deuteratedcompounds 23c ^j in the reaction sequenceleading to 30 take place and 23d clearly cannot be derived in a direct manner with yield and eliciency cornparableto those chrrr- from hydrolysis of a simple styrylchromium inter- acterizingthe conversionof 1 to 2. However, nlore mediate. Although the positionof the ring deuterium interestingfrom a ntechanisticviewpoint is the obser- atoms in 23c and 23d is not known with certainty, by analogy with the behavior of relatedorganochromium (.10)The interpretationo[similar rcactionsusirtg cts-styrylmagne sium bromidc was macieambiguous by lpplrcnt isomerizationof the olcfirric (19) The lbscnce of any sigrtiticant amoullt of the lrans isonrer of doublc bond ot'thc itrtcrmcdiatestyrylchrorniurn rcxgent. 234 excludes dccompositiort by any pitthrvay involving a free radical' (41) If carbol monoxidc is substitutedt'or 1-butyle in the reactiorr, C. \1. Whitcsides und C. P. Cascr'.J. .1mer. Chem..loc.,88,15'll (1966). fluorcrtoncis producedin a 4l I yictd.

lVltiresitles.Elttnunn | .2,i,1-Terrantetlt.,-lnaphthalene 5632 vation that the intermediate organochromium com- one further equivalent of the biphenyl Grignard pound present in solution at the point at which 2- reagent has been converted to a substance having butyne is added to the reaction mixture is not the carbon-metal bonds in both 2 and 2' posilions. These expected tris(2-biphenyl)chromium(III), but rather a observations strongly suggestthat 29 correctly repre- compound assigned the structure 29 on the basis sents the structure of the organometallicintermediate of analysis of products obtained by a degradation in this reaction. It is not clear from our data whether designedto establishthe locationsof carbon-chromium a tris(2-biphenyl)chromium compound or, €.g., a bonds. derivativeof chlorobis(2-biphenyl)chromiumor dichlo- Direct reaction of arylchromium reagents with ro(2-biphenyl)chromium is the compound from bromine yields a mixture of products, including which cyclization to produce the metallocyclic moiety aryl bromides and biaryls, and as such is unsuitable of 29 occurs. as a quantitative method of identifying the locations A number of sound precedentssupport the pro- of carbon-chromium bonds.a2 However, arylchro- posed formation of a metallocyclic compound of mium reagents react smoothly with mercury(Il) bro- chromium(III) by intramolecularattack on an adjacent mide, yielding the corresponding arylmercury(Il) bro- carbon site: uiz., pyrolysis of diphenyl(2-biphenyl)- mides.a2 The carbon-mercury bonds of these sub- aluminum yields the closely analogous 5-phenyldi- stances,in turn, are cleaved by bromine in high yield benzaluminole 31 :{{ reaction of azobenzene with to aryl bromide and mercury(Il) bromide.a3 Treat- potassium tetrachloroplatinate,{5palladium dichlo- ment of a solution obtained by reactionof 2-biphenyl- ride:{'i or nickelocene{6yields compounds of structure magnesiumbromide in turn with chromium trichloride, 32; and ar1,'iphosphinecomplexes of rhodium,{;'{B mercuric bromide, and bromine yields a solution iridium,{eruthenium.{i.50 cobalt,50 and ironsr'52under- containing 2,2'-dibromobiphenyl, 2-bromobiphenyl, go reactionswhich either require or implicate oxida- and biphenylin the yieldsshown in SchemeIV. Taking tive addition oi an ortho carbon-hydrogen bond the with of cyclic Scheme[V. Formationand Reactions of 5-(2-Biphenyl)- to nretal formation intermediates dibenzchromole(29) representedschenr.rticallv by 33. Theseand relateds3 examples have establishedthat formation of lour- + Crcl .;l'ftll.' or five-menrberedmetallocyclic rings by cyclization i.0t)crl uir' onto a benzenerins is a seneraland facile reaction u-rl-+-.'\/N*N-Ph

Ct{ Cr(lcl{ 32 <+- H(' CH l') h, .)< 30 \CJ PPh .' r,...... -/ ().S0 equ ir' Cr t%crAllltl rYvt I'L I I CO A I1 Ph + \N {t) hr.:15 33 34 29 O type. Combined with the experimentaldata sunt- 0.{Jequiv marized in Scheme IV. they make the structure 29 a very reasonableformulation for the stable organo- chromium substance formed under our reaction L _/ + \A_/ (4-l) J. J. Eisch and W. C. Ii;rska, J. Amer. Chem. ^Soc.,88,1976 Br ( 1966). 1.!5equir 131equiv (15) A. C. Copeand R. W. Siekmnn,ibicl.,E1,3272 (1965); scc also R. F, Heck,ibid.,90,313 ( 1968). + (.16)J. P. I(lciman and M. Dubeck,ibid..85, 15.14(1963); seealso N. W. Alcock, R. C. Spencer,R. H. Princc,and O. I(ennard,J. Cltern. Soc.,.4,2383 ( 1968). (.17)W. I(eim. J. Orgartornetal.Chenr., 14. 179( 1968). (.18)J. Chatt and J. rv-I.Davidsort, -/. Cherrt.Soc., 843 (1965), havc otr- BrBl servedoxidative addition of thc ciLrbon-h-"-drogenbonds of coordinatcd P-CHr and naphthalcncgroups to ruthcnium,and S. D. Ibekrvc,B. T. 0.95equiv I(ilbourn, U. A. Raeburn, aud D. R. Russell,Chent. Commutr..133 (1969),havc detcrmincdthe cr-'-ste[structurc of (c-CroHr)RuH[tCHr):- into accountthe slight excessof Grignard reagentused, PCH:CH:P(CHr):l: by X-ray difl'rrtction. (1967); and the presence o[ small amounts of biphenyl in (-19)}I. A. Bennettand D. L. \Iilrrcr, Cltetn.Contmwr.,58l J. Anrer.Chem. Soc., 91,6981 ( 1969). the solution of this Grignard reagent, these yields (50) G. W. Parshall,J. Anter. Cham..Soc..90, 1669(1968); G. \V. establish clearly that ca. I equivalent of biphenyl Parshrrll,W. H. I(noth,and R. A. Schunn,ibitl.,9l,.1990 (1969). has been produced (51) C. Hata, H. I(ondo,artd A. ltivake, ibkt.,90,2278(1968). at some stage of the reaction ofl (5:) A. Saccoand M. Aresta,Cltent. Comntun., 1223 (1968); seeelso Grignard reagent and chromium trichloride, and that P. L. Pauson,Pure Applied Chem.,17,235 (1968); lvl. M. Bagga,W. T. Flannigln, G. R. I(nox, P. L. Pauson,F. J. Preston,and R. I. Reed, (-12)W. Herrvig and H. H. Zeiss,J. Anrer. Chem. Soc., El, 4798 J. Chem.Soc. C.36 (1968). (re59). (53) R. I(oster, Aclcan. Organonretal.Chem., 2, 257 (196'l); R. 1'13)F. R. Jensen.rnd B. Rickborn, "Electrophilic Substitution of Kijster and ivl. A. Crassbergcr,,1ntt. Cltcnr., 719, 169(1968); D. Hell- Orgrtnomercurials,"\{cCras,-Hiil, NervYork, N. Y., 1968pp 75 tT. rvinkel.C he m. Ber.,99. 3660 ( 1966).

Jttttrnulol tlrc..7tnericctttChenticul Society' I 92:19 I Seotentber23. 1970 f a-{ -t 5633 at l,/ conditions by reaction of 2-biphenylmagnesiumbro- troscopy. Knowledgeof the isolatedyield and isotopic 7 mide and chromium trichloride. compositionof the benzene,and of the yield of tetra- The observation of the dibenzchromole29 as a stable organometallic intermediate and the demon- D J strationthat the reactionof 29 with 2-butyneproceeds cH ('-('('H Da- /-\ sTHF + smoothlyto 9,1O-dimethylphenanthreneobviously sug- -1lFCr gest that the reLrted chromocycle, 3,4-dimethyl-5- phenylbenzchromole(34;, might be an intermediate t) 35 in the conversionof 1 to 2. We have not been able to obtain clearcut evidence for this benzchromole as an interrnediure in this conv'ersion. Although the iormation of cis-2-phenylbut-2-ene-d2(23d) on trcrtmenr oi a reactingmixture of 1 and 3 with deute- rium oxide stronglvimplicates 34 as a solutioncompo- ncnt. the y'ieldoi 23d, and by inference34. is always methylnaphthalene-d,was sufficientto establishthat lor',. Thc-se i'ields are easily compatible with the >0.5 equiv of CoH:D1wils produced for each equiva- hvpcrthesisof 3.1 as an intermediateon the pathway lent of tetramethylnaphthaleneformed in the reaction. lcr..linsto retranrethvlnaphthalene,provided that the Sincesome of the benzeneproduced in this transforma- ri.rrer)i reecrir'rnoi 3-1with 2-butyne is rapid compared tion is held as zr-benzenechronrium(0)or chromium(l) wrrh lrs ri.tter'ri ftrrmation. However. in the absence complexes,and as such would not have been isolated oi trthcrerirrcnce. it is also conceivable.although un- as benzeneunder the conditionsused in working up lrkc'ir,.th.rt 34 rnirrittbe simply the product of a side these experiments,it appearsthat most or all of the r3:riilrrounrel:rtcti tt) the path connecting l with 2. o-hydrogen which disappearsfrom one phenyl ring Regardless.it is cleurthat the conv'ersionof 2-biphenyl- of triphenylchromium in forming tetramethylnaph- muqnesiurlbrornide to 9,lO-dimettrylphenanthrene in- thalene is transferred to a seconclphenyl ring and volvesinitial fornrationof the dibenzchronrole29 as ultimatelyappears as benzene. an intermediate,followed by subsequerrtreaction of At least three basicmechanistic schemes deserve con- this substancewith l-butvne. A sirlilar pirthwayfor siderationas possible descriptions of thecyclization step. tl'rc-conversion oI I to 2 seenrsvery probablc. The ring closuremight take placeby directinsertion of The kineticisotope eliccts. discussed earlier in ct-rnnec- the chromium(lII) atom into theortho carbon-hydrogen tion with the questionof the internrecliacvof benzvne- bond of the phenyl ring to give a chromium(V) hV- chronriumcomplexes in reactionof triphenylchromiunr dride (36) as an internrediare,followed by loss of withl-but)'nc. now bearreexarnination in lightof theev'i- benzene; it might take place by electrophilicattack dcnccindic:rtins thut the most significantintermediate by the chromium(U[) atom on the phenyl ring to is in fuct u benzchromole.forrrred by insertion of yield a o complex (37),, followed either by direct l-butr ne inrt-ri.r curbon-chronriunt bond followcd by loss of benzeneor by a l,2-proton shift to yield the crciiz.rrr,rn.The ,tbserrationthat thereis no isotope product of oxidativeaddition 36: or it might take place crl'c.'lt)r-l tite rc:rcri()nof conrpounds 18a-d with 2- by a processin which expulsionof benzenewas con- i:rrrl',i:C r: cntrrelr c(rnsistentwith this rlechanistichy- certed in some unspecifiedmanner with carbon-chro- ;r.J\: l( \t i. .r,l-irr.'r I r()v rtlecl t[rat the rate-deternriningste p mium bond fornration. l-,'r|'.c rc-tctlr)r'lt)cCLlrs before the cvclizl'ttion.Clearly, SchemeV. rriri. : snr.rilsc-condury isotope eflect would be ex- Formationof 1,2-Dimethyl-5-phenylbenzchromole nc;t:J to .rttiFrda nrechanismwhose rate-determining st.l \\lis inscrtiontrf 2-butyneinto the carbon-chro- orrecl - ox rdat ive nriunrbonJ of triphenylchromium to form 24, or co- add it ron rrrJrn.itic-'nrri l-butvne to the chromiunl atom of this Cr H CrPh, rrrctll ConlprrLlfld. Further, the postulate that the Jnttn 24 sltr$ Sr€pin conv'ersionof triphenylchronriumto tetra- electroph ilic nt.:tftrlnaphthulene involres coordination iubstltu!lon or insertion I / oi l-butvne. anci that the subsequentformation and furth':r reuction of the benzchronrole34 are fast, is cLrnsistentw'ith the failure to detect any significant builtiup oi internrediateorganochromiurn conrpounds Cr durin-gthe reection. P'h \pl, Nlechanisticinterpretation of the deuteriumisotope ell'cctobserved for reactionof tri(phenyl-2-r/1)tris(tetra- 36371 hydrotlran)chro rniu nr ( 17)with 2-butynereq uires knowl- l'lttl eclgeof the fate of the hydrogen atom lost frorn the I Z-"*-,' I orrho position of the phenyl rin_q. This information I ll ti +PhH { | was obtained by reuction of tri(phenyl-2,,1,6-rlr)tris- VC.A I (tetrahydro[uran)chronriunr(llI)35 with 2-butyne to I rn give among other products,tetramethylnaphthalene-d 34 and a nrixture of deuteratedbenzenes. The mixture of benzeneswas separatedfronr the reactionmixture, Comparison of the isotope effect obtained during and its isotopicconrposition determined by massspec- reaction of tri(phenyl-2-d)chromiunr(17) and 2-butyne

llt'hitesides,Ehmunn i I .).-1,1-Terromethylnaphtlwlenc 5634

with thoseobserved for representativeelectrophilic sub- action of I in THF *rth deuteriumfor 14 hr at I atm stitution reactions at aromatic carbon permits one pressureand 15' resultedin slow deuterolysisof the clear condition to be placed on the mechanismsout- carbon-chromiumbond. l ieldinga mixtureof benzene- lined in Scheme V: if intermediate37 does lie along dt (58\) and,-d, (41T) esthe primary organic products. the reaction path between 24 and 34, its formation The benzene-drdetecteci in this reaction is probably from 24 must take place in a rapid preequilibrium produced bv thernrallv induced homolytic scissionof step, and its conversionto 36 or 34 must be rate deter- carbon-chromiumbonds (ri some partially deuterolyzed mining. The a-deuterium isotope effect on the rate speciesanci retcrlon r'ri the resulting free or metal- of formation of a d comple.ris normally small in elec- complexedphcnr I rldiceisw'ith solvent. No deuteriunr trophilic substitution reactions, since little carbon- was exchangedinro the rnnhenylchromiumunder these hydrogen bond stretching takes place during attack conditions. of the electrophileon the ring.;r';; Thus, the isotope Reactionoi deureriumrrith 29 under similar condi- effect observedfor reaction of 17 with 2-butyne(k^lko tions resulted in lnalerst)uscleavage of the carbon- : 2.7)6uis too large to be compatiblewith rate-limiting chromium bond,sto vield biphenyl. However, if the attack of the chromium atom on the aromaticring. reaction wirh 29 w'as carried to partial completion, Further differentiation between the mechanistic al- and the remainine orgitoc-rchromiunrcompound con- ternativesof SchemeV is difticult on the basisof the verted to the correspondingaryl bromidesby reaction availableinformation. The differencebetween the two with mercury'(ll) bromide and bromine, mass spec- paths connectingcompounds 24 and 36 is primarily one troscopic anaivsis esrrblishedthat appreciabledeu- of timing in formation of the carbon-chromium bond. terium had beenerchanse..i into the rings. Degradation While it is clear from other work thar sor hvbridiza--addition of the biphenvlsestablished thar the deuteriumwhich tion at carbon is not required for oxidaiive had exchangedinro rhc chromium reagentshas beeri of carbon-hydrogen bonds to transition metals,57,58incorporatedpredomrnrnrlv or exclusivelyinto the l, there is no firm evidenceindicating rhar oxidativeaddi- tion of aromatic carbon-hydrogen bonds to metals C,H" does not in fact procced through intermediatesanal- t' ogous to 37 by a pathway involving initial attack of the metal on carbon rather than by insertionof the metal into a carbon-hydrogen bond. However, there is also no direct evidenceestablishing the intermediacy D,,I atm,15', 1{ hr of compoundsresembling eicher 36 or 37 in reactions HgBr, of these chromium compounds. Nevertheless,two lines of evidencelend support to the suggestionthat conversionof 24 to 34 takes place either by oxidative addition of a carbon-hydrogenbond to the chromium +qp atom or by concertedaddition-elimination, rather than w+a_o by a reaction resemblingelectrophilic substitution at Br Br Br carbon. (1.65equiv r ,0li equivl (0.1?equiv) The first of these lines derivesfrom an examination 94.0%d, l):r..)7,r d,) 80.5%do

tLl oi the reactionsof triphenylchromium(1) and 5-(2- 5.6"/"dr -, a/J I7.Wodt biphenyl)dibenzchromole(29) with deuteriumgas. Re- 4.0%d ) .i.:;.d, t.6% d2 (!a) Review:H-zo inset,Adt:an. phls. ory. chen,z, t6t us64r. posirions of the biphenvl ring (see the Experimental (55) For isotope ellccrs in intramoleculnr eleckophilic subslitulion -Section). -1",'' rerc t ions of several com p o Lrndsclosely relared ! o those consideredin rhis wo(k.oii., derivalivesoi :-tpn""yr-zlaro"."-"i.-ilj;;;. ;. ;;;;"r The pertinence of these results to the mechanism andP.PKlemchuk,./. ,.lz'e.. crs'. soc.,E0.1285(1958I o[ cyclization of 24 to 3{ dependson the resemblance t56) A relarcdrelclton, rhe rhermrl dccompsirionof merhyltris(tri- ^t ,'t. process which (phenyr.2{4phosphinclrhodium(i) toii, me.hane,and merhane-d,, pre- -' "^': by the carbon-chromium bonds surnablyorirz oxiaidve iddirion of an o.r,/rocff bon-hydroeen (deureiiirm) of the dibenzchromole 29 are converted to carbon- bondto rhodium,'erhibirsan isoropeerTecr of ksl&D< 4.2,as mea- deuteIium bonds tO the reverSe Of the reaCtiOn Se. suredby thcritio ofCH, to CH,D evotved{sce Erpcrimenlal Secrion). ;,,--^ Thisnumber is comparablewirh rheisorope efec! of 2.7observed for t*-..-e. in which the carbon-hydrogen bonds of the the reaclionof l7t! and suppo(s the contentionthat the reac.ionI - 2 immediate precursors of 19 and 3,1 are converted to proceedslia oxidative addhion. carbon-chromium bonds. At the very least the ob- R.P. -CH, \ ,/ servationthat deuteriunris exchangedinto the ortho Rh positions of the biphenyl groups demonstratesthat \eR, R,l/ carbon-hydrogenbond cteivageis reversibleuncler someconditions. The phenomenologicalsimilarit.v- of the isotopic ex- R,P. '\_/\ A\ \) change observedon trertment of 29 with deuterium ,Rh. \:(/ + cH, + CH,D to that observedby Parshall.Knoth, and Schunn for \p' \n,o) RP/ the o-hydrogensof the pheny'lrings oi HCo(Nr)(PPh3)' ,/\ 'R R' and related compounds50is sulficientlyclose to make ii the suggestionsof analogous mechanismsattractiv'e. Following proposed ex- R: o-CoH,D the scheme by theseauthors, change would take place bv oxidativeaddition of deu- (57)S. Bresadola,P. Rigo, and A. Turco, Chem.Commun., 1205 (1968);F. Piacenti,et al.,J. Amer. Chem..Sc,c.,90,6848 (1968). terium to 29 to yield a speciesrepresented schematicallv (58)M. A. Benncrtand P. A. Longstaff,ibid,,6266 (1969). by 35 followed either bv an irreversiblecleavage of

Jottrnul o/ the rlrnericun Clrcmical Societl, ,l 92.-19I September2J, 1970 5635 the chromium-biphenyl o .bond (35 -.- 36), or by a SchemeVI co.mpetingand porentiallyreversible cleavage of a chro- mium-carbon bond of the dibenzchromolJ(3S * 37). -r/ H- However, there is no // \\ direct evidencein this work (or -1 + indeedin much fCr.{r; ) zo' of the directlyanalogous work with d8 -\ "l'\o. complexes)tor discrerehydridic intermediatesderived from oxidarire addition. on the basis of evidence presently'arailable. these classesof reactionsmieht {cH,c-ccur take place b)' e reaction sequencein which oxidative addition ro form an intermediate hydride and sub- sequentelimrnation were separate steps, or by a process l.z-l'\n" anelogous to that labeled "concerted elimination" in CrAr.l Scheme !' in which addition and elimination merse" 39 to a singlestep:r j-.,t a.>-O fcn,c-ccH, D-CrtV t Cl lllt D/ I >-/\ Ar r'r--\_y') D 26 36 38 35 + d1, together with tl small quantities of more highly deu \,_ teratedmaterial. Deuterium incorporationinto a mes /-\ ityl group bonded Phar ) to chromium is in clear conrrast \__/ with the resultsof similar experimentsusing triphenyl- chromiunr,but is compatiblewith an intermediateie- sembling39. The o.xidativeaddition of a methyl car- D bon-hydrogenbond to chromium \ implicatedby struc- ture 39 has some precedent.{$,58,63However, re- \ : gardlessof the precisemechanism of formation of t\,/\,/ /-r / 26, the demonstrationthat the ability of organochro- 'l- mium reegentsto yield cyclic productsdoes not depend on the availabilityof an aromaticcarbon atom to act as one ring terminusprovides support for thosemech- anisms for cyclization which do not resemble aro- matic substitution.

H-Cr' Summary and Conclusions .tu \_- /-\ ,/-\ This work indicaresthat rhe conversionof triphenyl- \/\_/ chromium to tetramethylnaphthaleneon reactionwitlr 2-butyne place Ti:s SCCI'ri ciurtrmsupporting the hypothesisthat takes in three distinct steps: insertion cr)i'rr j;5i6n e'ri2{ to 34 requiresa stepinvolving oxidative of 2-butynein a phenylchromiuma bond of 1 to florma -l-lirrrtrn c'ri r carbon-hydrogen bond to chromium styrylchromium reagent; cyclizationof this styrylchro- mium i::rs.rlreedl' been mentioned in anotherconnection. The reagent to a benzchromole: and reaction of .rt.r.iricroi trimesity'lchromiumand 2-butyne cannot the benzchromolewith a secondmolecule of 2-butyne cr;irze b1' substitution at an ortho carbon-hydrosen to form tetramethylnaphthalene(Scheme VII). In brief 'otroti: summary, instced.cvclization takes place by attatk oi four kinds of evidencesupport this mech- :i'rr'rhrlgroup. ultinratelyyielding 26. The formation" anism. First, labeling experimentsusing 2-butyne- tri-rirrsproduct can be rationalizedusing a mechanism l,I,L-dr, product studiesbased on reactionsof o-, ffi-, and p-tolylchromium r crr srnrilarto that of Schemevl proceedingthrough a reagents.and deuterium kinetic sir-rnemberedchronrocycle 38, or by directlyclizaiion isotopeeffect determinations carried out with 17 and 18 tcr ths four-memberedchromocycle 39. Again, no ex- combine effectivelyto excludemechanisms involving pcrinrc'ntale'idence pro'ides direct support for either intermediatesof tetramethylcyclobutardiene-or benzyne- llrernati'e. Howe'er, reactionof trimesitylchromium like symmetry. Second,isolation of cls-2-mesitylbut- ri ith deuteriunrto partial completion, followed by deg- (63) iv{cchanismssimilar to rhosc outlined in SchemeVI provide a rlcllrion of the__rernainingorgirnochromium reagents rationalizarionfor productionof tetrapirenylcl'clopentadieneiii on reac- tion of trimethyltris(tetrahydrofuran)chromium rrsins nrercury(I[) bromide ancl bromine. vielded 2- with tolane.6{ brorrromesitvlenewith composition61.7 and 34.s% '{t %r/o . Ph ('s9)organolithium';0 and -magnesium60reagents, Ph('-rl'h. sodium naph- (cH-),crJTHF ,,Y thalidc,rtand hydroxidc io',0.rreact readily rvith-hydrog*n,pi"su-aory by a mechanism " involving nucleophilicattack. A retirea mechanism /vh mrght also be possiblcfor thc reaction of arylchromium reagenrswirh Ph hyclrogen. (60) iii I(. Claussand H. Bc.stian,Ann. Chem.,654,g (1962); W. E. Bcckerand E. C. Ashby,J. Org. Chent.,29,g54f-tqO+1. (6.1)H. Zeiss gl,6090 (61) and M. Tsutsuj,J. Amer.Clrcnr. Soc., (1959); S. Bank lnd T..4,.Lois, J..4mer. Cltem. Soc.,90,1505 (196g). iVI.Michma'a.d (6lt H. H. Zcrss,J, Organorneral.Clten.,13, p23 (196g); C. Wallingand L. Boltyky,ibi(t.,86,3750 ( tg6t). 15,t39 (t968).

-r,.-...--.-.t---t--^_r-.t-^r.- | ) 1 t 5636 SchemeVII. SchematicMechanism for Conversionof in which the chromium(lll) heterocyclereacts with Triphenyltris(tetrahydrofuran)chromium( [II) to 2-butyne to f ield tetramethylnaphthalene.At least 1,2,3,4-Tetramethylnap hthalene three alternative mechanismsappear corlceivablefor /n\ ('tl('-(-('H', reactionmight take placeby insertionof a (r this step: | rH-Cr.;]THF' oi l-buty'ne into a carbon-chromium \ \_/ /, secondmolecule bond to give a se\en-memberedchromium heterocycle r (e.g., 40), bv' a concerted.front-side displacement, or I -Phl{ by a Diels--Alderrerction. in which formation of both I L carbon-carbon bonds to the entering acetyleneoccur concurrentlr'. \\'e have never detected products in the reaction mixtures from the tormation of 2 or 30 :q which suggestconlpL)unds resembling 40 as a precursor; and on the basis rri this weak evidence,we prefer a [Q.,(] mechanism for incorporrtion of the second molecule LPhI of 2-butyneinto thc tetramethylnaphthalenering pro- ceeding throueh rn intermediateor transition state 2-eneand cis-2-phenylbut-2-enefrom reactingmixtures -11. of trimesityl- and triphenylchromium support the pro- resembling posed initiat insertion of 2-butyne into the aryl-chro- mium bond. Third, the isolation of cis-(phenyl-2-A- but-2-ene-3-d(23d) tollowing deuterolysisof a reacting mixture of triphenylchromium and 2-butyne,and the I facile formation oi 5-(2-biphenyl)dibenzchromole(29) on reaction of 2-biphenylmagnesiumbromide with chromium trichloride, provide evidencefor five-mem- beredchromium heterocyclesas reactionintermediates. \ Finally, severaldeuterium kinetic isotopeand labeling studiesappear to be consistentwith the proposed re- o.. actionsequence. I Ur The insertion of 2-butyne into a carbon-metal bond o# implicatedin the first step oi this mechanismis unex- o'[Y' ceptional, and deservesno further comment.6s Cycli- zation of the resultingstyrylchromium compound to a chromium-containing heterocycleis more interesting on two counts. First, it provides further support ''-,, for the supposition{'5that five-memberedmetallocycles /..', I'- are important as intermediatesin organometallicre- t t// actions. Second,the close analogy betweenthe ring- Ph closing and ring-openingreactions of the chromium- .t I (lll) compoundsexamined here, and sinrilarreactions of dB comple,res.suggests that the former may take Ex perimentalSectir,rn;l place by mechanismsinvolving oxidative addition of CeneralNlethotls. AII reactionsinvolving organometallic corn- carbon-hydrogenbonds to chromium. Oxidativeaddi- poundswere carried out in flame-driedglassware under an incrt for tion of an aromatic carbon-hydrogenbond to a d3 atmosphereof prepurrriednitrogen using standardtechniques handlingoxygen- and water-sensttivereagents. Ether and tetra- chromium(lII) ion to give compound formally con- hydrofuranwere distrlled from lithium aluminumhydride under a taininga dt chromium(V)ion hasno precedent.66How- nitrogenatmosphere immediately belore use. Dioxane was dis- ever, the stability of substancessuch as PhoCrlia,sT tilledfrom a dark purplesoiution of sodiumbenzophenone dianiorr. r2 LirCrzHrPh6,6s(CHr)oCrlii6e is sufficient to establish Triphenyltris(tetrahl'drofuran)chromium(llD (1) and 2-butl'ne- l,l,l-ds (3)to *'.t. preparedas describedpreviously. Trichloro- that chromium(III) is capable forming compounds of tris(tetrah]'drofuran)chromium(III) r,vas prepared using a procedu re containingmultiple carbon-chromiumc bonds. Cor- basedon that o[ Zeiss.rr The desiredquantities of anhydroLrs respondingcompounds of chromium(V)are not known chromium(III)chloride and tetrahydrofuranwere placed in a flame- as stable entities, but ntight not be prohibitively en- ergetic as intermediatesor transition statesin mech- (70) Mclting points wcre determinedusirtg I Thomas-Hoovercantl- anismsrequiring oxidative addition to chromium(IlI). lary melting point apparatusand arc uncorrected. Boiling points .rre uncorrected. Nrnr spectrawere run otr a Virrjan 4''60 spectromctcr. Only negativeevidence is availableconcerning the Inlriued spcctra rvere taken in sodium chloride cells using a Perkin- nature of the final stage of the proposed mechanism, Elmer Nlodet 2378 grating spectrophotomcter. Mass spectra wcri determined on a Hitachi-Perkin-ElrncrRfvlU-6D mass spectromctcr. (65) For examplesof additions of other organomctallicmolecules to All spectraused tor deuteriumanallsis'"vere obtained using a minirrt.rL acetylenes,see ref 3 and P. M. Maitlis, ,4dcan.Organometal. Chem., 4, ionizing voltage.?t N{icroanalysisr"as performedby Midwest NIicro- 95 (te66). lab, Inc., Indianapolis.Ind. Glpc anal-vses\!'ere carried out using lrr (66) Reviews; J. P. Collman, AccountsChent. Res., l, 136 (1968); F & !I N[odel lll0 tlame ionizatiorrinstrumcut. Samplesfor m;.ts; L. Vaska,ibid., l,135 (1968); J. P. Collmanand W. R. Roper,Adaan. spectroscopicanalyses were collected from an F & M Model 720 instru- Orgartontetal.Chem.,7,5-l (1968); G. W. Parshall,Accounts Chem. Res., ment equippcd rvith a thermal conductivity detector. Normally SE- 3, 139( t970). 52 or UC-W98 columns were usedtbr both analyticaland preparatirc (67) F. Hein and R. Weiss,Z. Anorg.Allg. Chem.,295, 145 (1958). work. (68) F. Hein and B. Heyn, ,V[otrutsber.Deut. Akad. lltiss. Berlin,4, (71) K. Bicmann, "Mitss Spectromctry-OrganicChemical Applica- 223 ( 1962) ; N a tur wis s e t u cha l't e tt,46, 321 ( 1959). tions." McGraw-Hill, New York, N. Y., 1962,pp 223 ff. Samplest'or gtpc, (69) E. Kurras and J. Otto, "I. Organometal.Chem.,4, l14 (1965); deutcriumanalysis were purified by takirrgcare to collectas muclt J. I(rause, Proccedings9th InternationalConlcrence on Coordination of the peakas possibleto itvoid isotopicfraction;rtiort. Chcmistry,St. lloritz, Scpt 1966,p 168. (7:) W. Hcrrvigand H. Zciss,"/. Org. Cltent.,23'1404 (1958). _s6_j7

dried flask. togetherwirh a small.quantityof chromium(Il) chloride to yield ll.5 g (87X; ot 1.2-di(methyl-r/;)naphthalene;shaving ' bp [-l-5 [ by weight of Cr(llltCl'].7r The mixture was heatedunder 6647 (0.10 mm); mass spectralisotopic analysis(8.3 eV) 94.4% nitrogen with stirrrng at a temperature between 50o and reflux tem- dq and 5.67; d'. perature until a homogeneous solution was obtained, typically 4-Chloromethr'l- 1,2-di(meth:,,1-rd)naphtha lene. Ch loromerhy la- l-2 hr. tion of 10.9g (67 mmol) ot' 1.2-di(methyl-d,)naphthaleneusing the (2). 1,2,3,4-Tetrrmethl'lnaphthalene The general procedure used procedure of Hewett.re wirh 20 e 6lO mmol) of paraformaldehyde for these reactions is based on the procedure developedby Zeiss.t2 and 100 ml of acetic acid yielded 8.0 g (60%) of 4-chloromerhy.i- g (1.3 The Grignard reagent.from 0.52 mmol) of bromobenzenein 1,2-di(methyl-r/r)naphthalenehaving mp 7.1.5-75"(lit.t, mp for an l0 ml of tetrahydroluran was added droprvise to 1.0 mmol of tri- undeuteratedsample 72'). chlorotris(tetrahydrofuran)chromium(tll)in l5 ml of tetrahydro- 1,2-Di(methy'l-r/r)-1-methy'lnaphthalene.The reduction of 7.5 g l'uran at -30'to rvhich hcptadecanehad been added (37 -l-chloromethvl-1,2-di(methyl-r4) as internal mmol) of wirh 1.6e@z mmol) standard. After stirring l-2 hr at room temperature,0.2 ml (ca of lithium aluminum hydride in 50 ml of THF was carried our using 3 mrnol) of 2-butyne lvas added and the solution stirred overnight. the procedure described tbr the reduction of di(bromomethyl-c/:)- Hydrolysis of a l-ml aliquot of the reactionmixture in I ml o( l0T, naphthalene with LAD. concentration of the ether extract yielcled aqueoLrs hydrochloric acid and analysis b1,glpc shorved a 50-75fi 6.0 g (q:%) oi 1.2-di(methyl-r/r)-.1-methylnaphthalenehaving mp f ield of tetramethylnaphthalene. Samples for mass spectralanaly- 49-50' (lit.7emp of an undeuterated sample,lg-50.); mass spectral sis were obtained by hydrolysis of tlre reaction mi,rture in l0 ml of isotopiccomposition (8.3eV) 94.3T( dtand 5.7,2 (L. l0 [ aqueous hydrochloric acid, concentrarion of the organic phase 2-Chloromethl'l-3,4-di(methyl-r/;)-1-methylnaphthalene. Chloro- under vacuum, and the collection of the 1.2,3,4-tetramethylnaph- methylation ol'5.5 g (31 mmol) of 1,2-di(methyl-r/r)-4-methylnaph- glpc. thalene from thalene using.l.5 g (150 mmol) of paralbrmaldehyde and 40 ml ol' prepare quantities To of 1,2.3,4-tetramethylnaphthalenelarger acetic acid rvas carried out using the procedure of Hewett.?e A than l0 mmol, thc sermeprocedure, modified by omission of the reaction time of .l days produced 2.2 g (32%) of 2-chlorometh-r't- product internal standard. rvas lbllowed. The obtained from con- 3.4-ditmerhyl-rlr)- l-methylnaphthalene having mp 87-88". cerrtration of the hydrolyzed reaction mixture was recrystallized 1,2-Dimethr'l-3.4-(dimethl'l-c/r)naphthalene(6). The reduc- Itom hexane to yield i0-50[ oi 1,2,3,4-terramethylnaphthalene tron ol' 2.0 g (3.9 mmol) ot' l-chloromerhyl-3,4-di(methyl-r/,r)-l- havingmp 105-106'; lit.rxmp 106''. methylnaphthalenervith 0.38 S ( l0 mmol) of lithium aluminum 1,2,3,,l-Tetramethl,lnnphthalene-c/o.Triphenyltris(tetrahydro- hydride using the procedure describedabove yielded 1.6 g (1009;) preltared lrrran;chromium(II[) lrom 73 gtq1 mmolt oiCrClr. 3THF oi I .l-dimcthy'l--t,.1-di(merh-v- l-rir)naphrhalene having mp I 05- I 06, rvas alloweci to react rvith 7.9 ml of 2-buryne-l,l,l-rlL(cc.5.0 g, (lit.t2 mp for undeureratedsamplc 106'); mass spectral isotopic 97 mrnol) lblloiving the procedure describedabove ro yield 1.2 g composition(8.3 cV) 9-.1.iTi r/oanti 6.5"i d,,. (6,1 mmol) ot' 1.2,3,-l-tctramethylnaphrhalcne-r/,;having mp 106- Degradirtion of 1.2,3,4-Tetr:lmeth!,lnilphthalene-r/c.A sample of ' (lit.t2 106.5 mp lbr an undelrtcratedsamltle 106'). The isoropic deuterated 1,2,-'1..1-tetrtmerhllnaphthllene(0.5 g, i.6 mmol) was conrposition ol' this rnaterial detcrminecl mass spectrometrically oxidizedusing thc procedureof Hart and iVlurray.re The resulting (ii.l eV) was l.-lll,/,,,93.|i''l r/5,rrrd 3.7iid,.tt oil,vmrxture ot'10. ll. and l2 rvasdissolved in l5 ml of methanol 1,2-Bis(hydrox!'mcth]l-rl.:)naphthalcne. A solution of 40 g and cooled to -lO'. Ozonc rvas bubblcd through the solution (0. l6 mol) ot' dimethy,lnaphthalenc-l,l-dicarboxylate?5in 200 ml of until the ctlluentgas turned an aqucoussolution ol'potassium ioclide dry tetrahydrolirran (THF) was cautiousl.'-added to 7.6 g (0.18 brorv'n (r'rr. 3 mint. Excess ozone rvAS removed by bubbling a mol) ot' lithiurn aluminum deutcricici'iin 100 nrl ol'THF over 30 strcam ol' nitrogcn through the solution briefiy. Ozonides lvcre nrin. The solutioll was heated at reflux tempcrature for 2 hr, reducedcatalyticall!'usrng -l(X) mg ol'52 Pd-C and I atm of cooled. hydrol.vzed. and madc acidic with 30'[ aqueous hydro- hydrogen. The mcthanolic solution lvas filtered and concentrated cltlorrc acid. The orgunic lalc.r rvas separated and the aqueous undcr vacLtumto yield crr.150 mg ol'an oil. To this oil was adclcd layer washed with 100 ml ol'chlorolbrm. The combined organic l0 ml of l0"l aqueous sodium h-"-droxide.and the mixture was layers were wirshcd with aqueoLts sodium bicarbonate, dried stirred lbr 2l hr at anrbient temperature. The solution was ex- (N'lgSOr), and concentratedto yicld 31.5 g (7917)of 1.2-bis(hy- tracted rvith 1.0 mI ol'decane and the decanesolution dried ovcr droxymethyl-r/,:)naphthalenehavirrg mp l:18.5-149.5'(mp of an 4A N,IolccularSieves. Samples of meth_,-lisoprop,vl (14) '). ketone Llndeutcrated sumple l-19-1.19.5 lbr mass spectr.rlanalysis rv'erepurified by glpc using an SE-l() ,.ltrul.ol unrleuteratcd samplc Calcd lbr Cr.rHr,:O:: C, 76.57; column. The mass specrrllntol' l{ prepared in this manner lionr H.(r.-l-1. Fourrcl: C,76.61: H.6.-19. undeuterated tetramethy,lnuphthalenervas iclcnticalrvith that ot' an l.?-Bis(bromomcth-"-l-rl.1)n:rphth:rlene.To a m:xture of 20 g authenticsample oi l.l. (0.11 mol) ol' 1.2-brs(hy'dro,rymeth,"-l-tlz)naphtlraleneand 50 ml ot' Reaction of Tri-nr-tol1'ltris(tetrahvdrofuran)chromium with Z- benzeneat 0' was added l0 ml(ca. a threelbldexcesst of phosphorus Buty'ne. To a soh-rtionol'1.0 mmol of CrCl,.3THF and 0.211g oi tribromide. The mixture was warmed to room temperature, eicosanein 20 ml of tetrahydrofuranat -,'i0'was added the Grrg- stirred tor 8 hr. poured onto ice. anclextracted with 50 ml of chloro- nard reagent prepared tiom L2 g (7.Ommol) of nr-bromotoluene in lbrrn. The chloroform solutron was washed rvith aqueous sodium I 5 ml of tetrahy'drofuran. After stirring the reaction mixture lbr (NlgSO.,), bicarbonate,dried and concentratedto yield 31.5g (87%) I hr at room temperature,0."lml(ca. 6 mmol) of Z-butynewas added ot' I .2-bis(bromomethyl-r/.:)naphthalene hav'ing mp 148.5-149.5" and the solution stirred lbr l0 hr. A 2-ml aliquot of the mixrure (mp ol'an undeuterateclsample prepared by an aiternativeproce- rvas then quenclred in I ml oi 10'T aqueoLrshydrochloric acid anci dure;; I 48.5-1.19.5 "). analyzedby'glpc. This anal.'-sisestablished the presenceof 0.186 g 1.2-Di(metlryl-r[)n:rphthalene.A solution of 26 g (82 mmol) of (17.0i;) of 1.1.3..1.6-pentamcrht'lnaphthaieneand 0.0203 g (5.1T) 1.2-bist'bromomethyl-rl)naphthalenein 500 ml oi dry THF was oi 1.2.3.4.5-pentamethylnaphthalenein rhe reacrionmixture. added to 3.8 g (90 mmol) oi lithium aluminum deuteridein 200 ml 1.2.3,4.5-Pentamethy'lnaphthnlene(15). Tri-a.tolylchromium ot'tetral-rydrolr.rranover a periocl of 30 min, dr,rringrvhich time the (2.04 mmol) was prepareds0anci allowed to react rvith 2-buty,ne solLrtion began to reflu.x. Retiu.ring rvas continued with external ibllorvingthe procedureused lbr the nr-rolylisomerto yield 220 mg heating lbr an additional l8 hr. The solution was hydrol.vzed, (607;) ot' 1.J.3.J.5-penramerh)'lnaphthalenehaving mp 7V7l' : made acidic with 30"1 hy'drochloric acid. and the THF removed nmr (CDCI.,) o -7.0-8.0 ppm (nt. --1.aromatic),812.75 (s, 3), 2.60 undcr vacLlum. The residue was c,rtractedwith ether and the ether 15.-r) 1.50 (s. ,1) and 1.28(s. 6). laler dried (NlgSOl), concentrated. and distilled under vacuum

(71) Thc chrornous ittn Lrppearsto clralyzc the dissolution of tri- (78) An undcutera(c'd sarnplc prcplred bv this sequenceexhibited an chltrrochromium(lll). In Zciss's procedures sn.ralIquautities of chro- ir spcctrurn idcntic.rl rrith a cornnrcrcial sample obtained from I( & I( I nrotrs ion \!crr: gcltcrittc(l i/l situ bv rcduc(iort rvith zirrc, For sma[l Laborltor ics. t scrrleprcpariltlons, thc proccclurc dcscribcd here is the more convcnien!. (79) C. W, Hc,,r'ett. J. Chent.Soc., 19l (19.10). (7-l) Isotopic cornpttsitions reportcd throughout the e.rperimental (80) The o-bronrotoiucnc uscd in this expcrirncnr was prcpared bl scction arc dcrivcd I'ronr inrcnsity data corrcctcd tbr trC. The ionizing esteriticationol'o-[,.romobenzoic ucid, reduction ot'the ester with LAFI , volti.lgeat rvhich spcctra u'crc takcn was such that thc intensity o[ the brominltion ot'thc alcohol rvith PBr.r,anct reduction of the dibromidc - Il I pcak rvasncgligiblc. Any molccular ion had relarive abundance rvith LAH to giv'eisomericailv pure (>99 i by nmr) o-bromotoluene. <1.0T, if not rcportcd cxplicitly. (81) This aromatic multiplct *'as analyzed as an ABC spin systcnl (7,s) E. F. Bradbrook;rnri R. P. Linstcad. J. Chun. Soc., 1739(1936); using thc itcrativc nrnr program LAOCNJ:Er 6r : 7.80,6s - 7.19, R. IIcicr and H. C. Lottcr, Chenr.Ber.,9O,:2: ( 1957). il; : 7.1l,-/.rB : 3.3 FIz,Jtr: : 1.9 Hz. Jsc - 6.9 Hz. The magnitudcs ( 7(r) Purchuscd frorn i\le rrrlHy drides; isotopic purity 99 [ deutcrium. ot'thcsc coupling cons(itnts ilrc consls(cnt rvith thosc expected for 15, (77) \!'. Rie ti and I'1.[Joclcrr, L-lrctn. Be r.,89,70tJ ( 1956). irut are rncorrsistcutrvrth thosc cxpceterl tbr l6.Jl

ll' Ir i t,,.si tlt s. E/trrttur rt 5638 TabletII. Yields and IsotopicComposition of Calcd for Cr;Hrr: C. 90'85; H' 9'15' Found: C' Anal. ietramethylnaphthalenesIsolated from Reactionof H. 9.07. 90.86; 2-Butynewith 184-d 1,2,3,4,6-Pentamethylnaphthalene(16)' Tri-p- tolylchromtum . 2-butyne f .OS mmol) *u, ptipured and allowed to react with -TetramethY'lnaPhthalefl€- f yield 148mg iollowing the procedureused for the nr-tolylisomer to Isotopiccomposition' I Isotopeeffect' having mp 85-86"; ,ts/&ob i;;i; & 1,2,3,4,6-pentamethvlnaphthalene Time," min Yiel.l. % ,io d, * r/, 2'53(s' 6)' 2'50 icoclrj 6 -7.i-s.t pp- (m, 3. aromatic)'84 ' 11 5()5 .19 5 0.97 (s,".i 3 and2.30 (s' 6). 2.0 '-'),'it.), c' 50 l 49.9 0.96 calcd lbr CriHrsr c, 90.85; H. 9'15' Found: 3.5 JI !l 19.5 0.97 9O.72;H.9.40. 5.0 9t _\(J.) 1l .19.5 0.97 Chlorobenzene-Z-d.A mixture oi 100 eQ.42 mol) of .l-chloro-2- 90 )(J ) ml of deuteriumoxide, and 80 g b iodobenzene.200 ml otdioxane.80 to the solution of 18a-d' Ob- and the organiclayer " Time after adding 2-but}nc of zinc powderwas relluxed for 7 hr, liltered. composition of the,mixture ml of etherand tained by comparison with the isotopic ,"por"t.O. The aqueouslayer rvas with 150 -rl; mercuration and "vashed portions of bromobenzene-r/0, -clr, ord obtained by the combinedether layers were washedwith two 100-ml througha bromination of 18a-d. of *u,.., dried(Mgsor), anciconcentrated by distillation a 50-cm i0; Vigr.u* colJmn. The residuewas distilledthrough ,pi""i"g i"nd column to yield 2g.l g (57%) of chlorobenzene-2-d: do- obtained by' mercurationand brominationof tlie thismaGrial has mass spectral composition 97.1 /' d1.2.9/o bromobenzene prepared- of l8a-d. Bromobenzene-2'c/.benzoic-2-ri acid (10 g' 82 mmol)-' startingsolution Hauser8s of Trimesityltris(tetrahydrofuran)chromium(IIDwith from N,N-dimethylbenzylamineby the procedureof Reaction A solution ot 6.3 mmol of trichlorotris(tetrahydrofuran)- urlng Uutyllithiumin a 3 : I hexane-ethersolution as metallating Z-gutl"r". (10.7g, usingthe in 100ml oi THF to rvhich0.7156 g of hexadecane agent.was converted to bromobenzene-2-r/ 84f) cLrromiumtIII) -30'. internal glpc standardwas cooled to piol.,iur. of Oppenheimerand Bergmann;86this material had mass had been added as the Crignardreagent solution prepared iiotopiccomposition eV)98' | 1i d.' l '97' do' To this solutionwas added lp..tro..opic' J9.'0 (20 and an excess.of mlg- of Tri(phenil-2-ri-)tris(tetrahydrofuran)chromium(IIl) trom.l.0 g mmoll of l-bromomesitylene Reaction reactionmixture was allowed tcl A solution oi 63 mmol of trit pl'renyl-2-r/)chromium- nesiumin so ml of THF. The with 2-Butyne. u,ith apl]earanceof a characteristtc (tii) *as allorvedto react rvith 1.5ml (ca. 160mmol) of 2-butvne warm to room temperature, solutionat room temperaturefor l proceduredescribed above tbr reactiono[ undeuterated bLuecolor. After siirring the iri,ig the wasadded. The courseof thc A sample of thc resulting tetramcthy[- hr. 1.5ml (c'. l7 mmolt o12-buryn. i.ipti.nVt.f,romium. glpc of glpc, had mass spectrosco'icisotopic ensuingreactton \r,'asmonltored by analysis -hydroly'zed nopf,ifrof.ne,isolatecl by foilowed bv 'i'r' aliquolsand rvascomplcre atier 0.5 hr. Hydrolysis, composition(8.8 eV) 7l .6 ,h,28.'1li tltat rvasadded over I isolarronand spectroscopicanalysis, established [fromobenzene'r/,,.Bromine (60 g, 0']7 rnol) componcnt (25)'" g of iron filings' ieaction 0.771g (70",;)ol'cis-2-mesitylbut-2-ene hr to 25 c (0.3 mol) of benzcne-r/rs7contatning I the l.ielded and bp +j-+-l' (0.01Toirt, and 0.223s el%) of a compound' The solutronwas poured irrto 5()rnl ol' I N sodiumhydroxide having (26) (lv{gSOr),and ZOIZI:,(0.0-l Torrt. deducedto be 2,3.-1,6-tetramethylindene hlterecl. The organic layer was separatcd.dricd Up (s' 55-56"(15 the basisof thc follorvtngevidence: nmr (CDCh) 6 6'89 Jistilledto vieldlq g fsi'T) ot' bromobenzene-c/"bp on 6.70 (s. l. aromatic),1.06 (broad singlet, 2. cH)), Torr); massspcctral isotopic cornposition 95'8 "l tl'"1'2/" d* l, aronraric), (coFls):- l.ll (s.3. ArCHr), 2'15 (broad singlet' 3'2-CH')' Rcaction of 2-tlut1.newith a Nlixture of (cnt[;)rcr, Z.+Sfs, 3. ArCH,). spcctrum(70 eV) mle l'12 (molecular (CeDr)Cr.(Cotl,)(Cod,)rCr, and (C,;D,),Cr(l8a-d). An approxi- 1.98(s. -1.3-CHr), mass n.,u,.iv I : i mixture ot' bromobenzcne-r/,rand bromobenzene-du ion). for *ut pr.p"red (49.67i, ,lr' 50.4%da { cl',r8)'The Crignard reagent ,ltrul. Calcd soluiionprepared irom t.l g-(ca. 7.0 mmol) of this mixtureof 90.58: H,9.-16. a reection mirture with deLrteriumoxide yieldcd bromobenzenesand magnesiumin 20 ml ol'THF wasadded drop- Hydrolysis of having isotopic composition (9.0 ev) I :'; wiseto 1.99mmol of 1 in 30 ml of tetralr-v-drofuranat *30o, con- cis-2-mesitylbut-2-enc J5"-.,tl '. taining 0.1693g of heptaclecaneas an intcrnal standard. After dt,54'\r/r,and ci.r-2-I'henylbut-2-ene(23) from Rqrction of l- lnd stirrin-glbr I hr it ,oom temperature.a l0-mlaliqrrotot-the resulting Isolaiion of 20 mmol of 1 rn 2(x)ml oi THF was added3.0 rlll solutionoi l8a-d was addcdto 1.0g ot'mercury(ll)bromide, the 2-Butyne. To of 2-butyne. Fiiteen.minutesafter the beginnrrrg resultingorganomercuriai rvas cleavetl witft an excessof bromine, l.*-lS mmol) reaction( l()5min afterthe addition of 2-butynet' and the excissbrominc was decomposedby addition9f l0 ml of oI theexothermic oxidervas added. The mixturewas poured into ioZ socliumbisulfite. After concentrationof the organic 2.0mlo[deuterium acidirnd extracted with 20 ml of ether- pnaie"qu.ous undervacuum. a sampleof bromobcnzenewas collectedby 100ml oi l0% hydrochlorrc washedthrec trnrcswith 50-ml portionso[ water. glpc for massspectral isotopic arralysis: 48'8 molii dn * d'' To The ether rvas (ca. (NIgSO*).and concentrated.Deuterated crs-2-phenylbut-l- ihe remainderof the solution of 18'-d was added0.5 ml 6 dried by glpcin -2'" overally'ield' based on chromium' mmol) of 2-butyne. Durirrgthe courseo[ the ensuingexothermic enewas isolateci isotopiccomposition (8'8 eV) was 32"1T' reaction.l0-mlaliquots of the reactionmixture were quenched in 5 Its mass ,p..t.or.olic and 22.27"dr' An undeuteratedsample prepared ml of l0d aqueouihyclrochloric acid and the yieldso[tetramethyl- ir, +5.+1i'dr, proceciurehad an ir spectrumin good agreement naphthalenedetermineci by glpc. After concentrationof each b:- an onologout vacuunt.samples of 1.2.J,4-tetramethyl- with that of an authenticsample.Be tuenched aliquot under mixture of by gtpclbr massspectral isotopic analy- Degradation of Deuteratedcis-2-Phen1'lbut-2-ene. .A napirthatenewere collected mg (1'0 mmol) oi are summarizedin Table III. S0 rri of deuteratedcis-2-phenylbut-2-ene' 160 sis. Yiclds and isoropicanalyses for 2 hr. comparisonof the iso- porasslumpermanganate, inci 20 ml of waterwas stirred The kineticisotope etlect was obtainedby and with that of the Excesspermanganate was decomposedrvith sodium bisulfite topiccomposition of the tetramethttnaphthalene and the solutionrual filtered,macle acidic with hydrochloricacid. extractedwith 5 ml of ether. The etherwas concentratedunder v&cuumand benzoicacid was isolated ttom theresidue by collectron (82) A. A. Borhncr-Bvanci S. lv{.castcllano in "computer Programs from glpc. This material haci massspcctroscopic isotopic conr- York' for Chemistry,"Vol. I, D. F. DeTar' Ed.. W. A. Bcnjirmin,New position(8.8 eV) M.2% drand 55'8 [ r/q' N. Y., 1968,p 10. Reactionof Tris(2,2-diphenylethenl'l)chromium(Ifl)with 2-But1'ne' (S3) A. A. Bothncr'Rv' Adcatt' .\laqn. Ilesonance,l, 195 ( 1965); (23 ot' The Grignard reagentsolution prepared from 6'0 g mmol) S. Sternhetl,Rea. Pure .4ppl. Chem., 14, l5 (1964). of : unti t*tttt magnesiumin-30 ml (81) Analysisof this muttrptety'ietdcci 6t' : 7'96,6s : 7'86' 6c 2-bromo-l,l-diphenliethylenet '1 of 6"1 mmol of CrCh'3THF arrti 0.8Hz. /rc : 9'8 Hz, Jrt,:: l'l Hz' Thesecouplingcon- THF was addedto a solution .23,J$: 60 ml of THF at -30'' Ttr .rrecompatiblc rvith 16. 0.181g of eicosane(glpc stan

2_t.la70 5639

temperature and stirred for 2 hr.. Analysis of the mixture by glpc ITI showed the presenceof 0.155 g (ll%) of a product identified by comparisonof its retention time and mass spectrum with thoseof an aurhentic sample oi 1.2-dimethyl-4-phenylnaphthalene(28). Hy- drolysis oi the reaction mixture, concentratron. and extraction with erher yielded 1.0 s Q5% based on chromium) of a white solid, slightlysoluble in etlter.which was identifiedas 1.1,4,4-tetraphenyl- butadiene by comparison of its ir spectrum with that of a known lnn sarnple.er 1.2-Dimeth yl-4-phen-'" Ina phthalene (28) was prepared by oxidative 2 ln\nq/ coupling of a mi.red copper([) ate complex.e Solutrons of phenyl- AilII lrthium prepared ltom l5 g (9a mmol) of bromobenzene and excess lithium rvirein 100mlot'ether, and of 4-lithio-1.2-dimethylnaphtha- lene. prepared from 2.6 e ( I I mmol) of .l-bromo- l ,2-dimethylnaph- thalene;eand lithium rvire in 30 ml of ether, were added to 7.2 g (:() mmol) of copper(l) bromide at 0". Oxygen rvas bubbled through the solution at 0' for -5 min. and the reaction mixture was rIIIilil rilll hrdrollzed rvith 50 ml of water. The ether layer was separated, dried l\{gSOr), and concentrated. Much of the biphenyl formed rvt/ as the major product of the reaction was removed b_vsublimation at 70' (0.1 Torr). The residue liom the sublimation rvas distilled under !'acuum to yield 0.8 g (34[ basedon naphthaleneprecursor) oi l,l-dimethyl--l-phenylnaphthalenehaving bp l2l.-l' (0.05 Torr) and nmr (CDCI) 6 7.1-8.2(m, 10, aromatic),2.70(s,3, CHr), and2.13 (s, 3, CH'r). .-ltttt/. Calcd lbr CrsHrol B 91.91:H. 7.06. 5-(2-Biphentl)dibenzchromole (29), and Its Rcaction with 2- Butl'ne. The Crignard reagentprepared from ().8221g tl.5l mmol) ot'l-trrtrmcrbiphenyland excessmagnesium in l5 rnl ot'THF con- rrinirrg 0.1707 g of heptadecaneas internal glpc standard at ca. -l-i"r: *as slorvly'adcledto a solution composed ot' l.()8 mmol of CrCl'.lTHF rn l() ml ol'THF at -10', contitining0.1093 g of ei- .osanc rs r secondinternal glpc standard. At'ter the solution had warnrcd to room tempcrature and stirred lbr I hr, a l0-ml aliquot r',asallorred to rcact rvith 0.5 g ol'mercurr-(il) bromrde at room tcrn[)craturc. Bromine ( 150mg.1 was added to the resultingmixture ol'orglnomercur! compounds. and the solution unaly'zedby glpc lbr bipheny'1.l-bromobipheny l. and 2.1'-dibrornobrphcnyl. ni11 To thc remainingreaction mixture rvasaddcd 0.2 ml (ca. 3 mmol) llr / ol'l-but1nc. and tlie solution was stirred lbr fi hr at 15'. A l-ml lliquot w'as hy'drolyzedrvith 5[ hydroclrloric acicl and analyzed C l'or 9.lt)-dimethyll;irc'nanthrenee{by glpc. A l(Frnl aliquot ln rvns rv'orkcd up rvith mercury(ll) bromide using thc procedure ticscrrbcdabov'e . Products rvere isolated by glpc and identified by cornplrrisonot' ir arrdmass spectra rvith thoseot' authentrc samples. rlW Irr a scparilte experiment irr which the reaction mixture was tlLrcnchcdw'rth deLlterirrrl oxide, mass spectrutlanal_rsisoi the 9.10- il drrncthllf.hcnantltrcnc formed showed no incorporation of deu- tcnurl1. I;luorenone. A solution oi 2.05 mmol oi 5-(2-biphcnvl)dibenz- chromole t29) in J0 rnl oi THF, containing0.1-lJ6 g ot'hcptadecane as internal standard. prepared as described above. was stirred /\t 1n tt r ior I hr at room temperature. After stirring lbr an additional 40 . r/ I /\ hr urrder an utmosphere of carbon monoxide at room temperature, r1ilYIi1 AI a l-ml alrcluot rvas hy'drol1'zedrvith I ml oi l0'l aqLreoushydro- /ln/lll'li /tt cirloriclcrd and anallzed b,v'glpcto show 0.153g (42[ basedon /l chromium) ot' flLrorenonL-.The remaining solutron was concen- I il tratcci under vacuunr. h1'droly'zed.made acidic w'ith 20'i aqueous D I tt i hytirochlorrcacrd. and extracted with l0 ml of etltcr. The ether solution was conceutratedand a sample of fluorcnonc.collected by l glpc. rvasshorvn to cxhibit an ir spectrum matching that of an au- I hln/ thenticsample. Re:rction of Tri(phcn1'l-2.4.6-r{;)chromium (35) rvith 2-Butyne. I A solutionot'1.0 mnrol ot'CrClr.STHF in l0 rnl ot'tetrahydrofuran containing0.0761 g ot'lreptadecaneand 0.2136 g or decaneas in- ililil

(9l) SacltlcrC.rtaloguc, spcctra no. 1,125-i,:05 t l. (91) G. \1. \!'hitcsidcs.\V. F. Fischcr,Jr., J. Sln Filippo,Jr., R. W. lloo 700 Brrslrc.auti H. O. HoLrsc,J. .1ntcr.Chetrt.Soc.,9l. -{lJ7l tt969); G. }t. 900 \\'iritcsirlcs,J. S.rrtFilippo, Jr., C. P. C.tsey',and E. J. P.rnek.ibid., E9, 53ol( r967). cm' t9l) Tire solubilityot' biphenyl-l-magnesiurnbrornidc in THF is in- corrlerticrrtlylorv itt lcrnpcrature<.10'. Figure 1. The infrared spectraof biphenyl-dobtained from the (94) An authentic surnplcof 9,10-dimethylpltcrtartthrenc,mp 142- with deuterium(A) and from mixtures l+1.,(',\\irs prcpilrctl usirrg literaturc proccdurcs: C. A. Dorrntctd,J. E. reactionof 29 of biphenyl-ri, -25 (B), (C), C.rllcn..rndC. l{. Colerrrart,"Organic Synthcses," Coll. Vot.III, Wiley, with /" of biphenyl-?-d biphenyl-3-d and biphenyl-4-c/ \crv York. \. \'.. 195,i,p ll-l: U. !l. iVlikhail()virnlt N. C. Churnova, (D). Bandscharacteristic of eachdeuterated sprcies are indicated J. Gett.Cirt'tr. L'.5511, : l. l6i9 ( l95l). on the spectra.

Whitesides.Elununn 1.2.-j.1-Tetratncthylnaohthalcnc' -- .--'

5640 - ternal standardswere cooled to 30" and 3.8 mmol of phenyl- (CCl{) of mixtures of biphenyl-r/nand thesecompounds in the 65G_ 2,4,6-drmagnesiumbromidees in l0 ml of tetrahydrofuranwas I100 cm-r region are reproducedin Figure l. addedslowly. After stirringthe reactionmixture for l2 hr at room Determination of the Site of Deuterationof the Biphenyls Obtained temperature,the reactionwas quenchedwith 2 ml of 5 M hydro- by Reaction of 29 with Deuterium. The crude mixttre of organrc chloric acid. Analysis by glpc showed ll2 mg (1.44 mmol) of products obtained by reaction of -5 mmol of 29 and 3 mmol of D: benzeneand 89 mg (0.48mmol) of 1,2,3,4-tetramethylnaphthalene.for 14 hr at 25", followed by reaction with mercury(Il) bromide and The reactionmi.rture was then diluted with 50 ml of waterand ex- bromine. was distilled through a short-path column to separatethe tractedwith t0 ml ot. ether. The ether extractwas washedwith biphenyl derivatives l'rom nonvolatrle inorganic and organometallic 50 ml of water, dried (MgSOr), and concentratedby distillation substances. This drstrllate.whrch included the major part of the through a 30-cm Vigreux column. Mass spectralanalysis of a biphenyl, 2-bromobrphenyl. and 2.2'-dibromobiphenylpresent in sampleof benzenecollected by glpc shorvedisotopic composition the crude reaction mixture. was allowed to react with excessmag- 157, d4,83.3 % dj, aod | .77( d2. nesium in 5 ml of THF. The solution was cooled to 0o to precipi- Reactionof Triphenyltris(tetrahydrofuran)chromium(Ill)with Dr. tate the biphenyl-2-magnesium bromide and biphenyl-2,2,-di(mag- A solutionof 2.0 mmol of triphenyltris(tetrahydro[uran)chromium- nesium bromide), the precipirarewas compacted by centrifugation (tII) in 25 mt of tetrahydroluranwas stirred lbr 90 min at room at 0o, and the supernarant solurion decanted. The solid residuervas temperaturein a 125-mlflask under an armosphereof deuterium. allowed to reacr rvith -l ml of r!'ater,and the resulting biphenyls Approximatelyone-half of the solution was added to 1.5 g of isolated using convenrional procedures,and purified by sublimation mercury(ll) bromide and the resulting mercury compoundswere (mp 67*70"). The rsolaredricid oi biphenyl was -100 mg; its cleavedrvith an excessof bromine. Excessbromine was decom- irspectrum in the 6-i0-1100cm-r regionis givenin Figure l; mass posedwith l0 ml of a 10% aqueoussodium bisulfitesolution. spectralisotopic anah sisshorred 81.0'T do, l7.17o dr, tnd 1.5% dl. The solutionwas then diluted with 50 ml of water and extracted Reaction of Trimesitl'lchromium rvith Deuterium. A solution of with l0 ml of pentane. The pentanewas concentratedand a por- 1.0 mmol of trimesin lchromium;3in 25 ml of tetrahydrofuranwas tion of bromobenzenewas collected by glpc. lvlassspectral analy- stirred under I atm oi deuterium in a 100-ml flask for 12hr. The sis establishedits isotopic compositionto be >99.57, do. The solution was then added to 1.0 g of mercury(ll) bromide, followed remainingtriphenylchromium rvas stirred a total of l:l hr, poured by O.2ml of brominc. Excessbromrnc rvasdecomposed with aque- into 100 ml of water, made acidic wirh hydrochloricacid, and ous sodium bisulfiteand the resLrltirrgmi,rrure poured into 50 ml ot' extractedrvith l0 ml of pentane. The pentanesolution was con- water and extracted rvrrh i5 ml of ether. The ether was driecl centratedand benzenewas collected by glpc. \[ass spectralanaly- (VtgSOr) and concenrrlrcd under vacuum. A sampleof 2-bromo- sisestablished its isoropiccomposition to be 57.6% & and42.4fi tlo. mesitylene. purified bv glpc, was anal-vzedby mass spectromctr!' Reactionof 5-(2-Biphenyl)dibenzchromole(29) with Deuterium. to show 61.7\ c/n.lJ.S'\ ,1,,0.6"; dt, 1.37i d3,0.9% d$ 0.67, The same generalprocedure was used lbr severalexperiments. /s, ood a trace ot'r/6arrd r/r isomers. The Gngnardreagent obrained liom 3.5 mmol of 2-bromobiphenyl Tri(phenyl-2-ri)phosphine. ( Phen.v-l-2-t/)magnesiumchloride,,vas was allowedto reactwith 1.0 mmol of CrClr.STHF at -30o in prepared by retluxing l5 g l().1.1mol) ot' chlorobenzene-2-c/rvith THF as describedpreviously. The nitrogenarmosphere over the 0.4 g tO.l7 mol) of porrderedmagnesrum rn 150ml of THF for 4 hr. organometallicsolutiort was replacedby deLrtcrium(l atm), and The Crignard reagcnt ',vasthen dccantedthrough a cannula, cooled the mixture was allorvedto warm to room temperatureand stir to 0o, and 3.2 g (0.011 mol) of phosphorustrichloride was added tbr the desiredlength of time. [t rvasrhcn tprcnchedby addition droprvise over 2() mrn. The strlution was rvarmed to room tem- to 1.5g ot'mercury(tl)bromide lbllorved by- bromine. Themixrure peratureand h:"droly'zcdrvrth 100ml ot'20'{ aqueousammonrum rvasfiltered and concenrrated. Samplesof biphenyl,2-bromobi- chloride, the la1'ers wcre sepuratcd, and the aqueous layer rvas phenyl,and 2.2'-dibromobiphenylused lbr mass spectraIdeute- washed with 30 ml oi ether. The cornbined organic layers were rium analysisrvere rsolated by glpc. dried (iVtgSOr),concentrated under vacuum. and the last traces ot' Qualitatively.the extentof dcuteriumincorporation into each solvent were removed by heatrng tlre resiciueto 60'(0.1 Torr) lbr of thesematerials depended on the e.\tentto rvhichthe reactionof l0 min. The residue was cr;-stallizedl'rom ethanol to yield 5.2 g 20 rvithdeuterium was allo',ved to proceed.the higherincorporation (857l of tri(phenyl-2-r/;phosphrnchaving mp 79-80"; mass spec- into the 2-bromo-and 2.2'-dibromobiphenylbeing observed after tral isotopicanaly'srs : 0.67i .1t,7.4 "l r[. and 92.1% d3. longer reactiontimes. The most extensivcincorporation into Tris[tri(phen1'l-2-r/)phosphine]rhodium(I)Chloride. Tris[tri- thesematerials was observedin materialsisolated ltom reaction (pheny'l-2-r4phosphinelrhodiumtl)chlorrdc was prepared in 961 between-l mmol ot'20 and 2 mmol of D: carriedout at 25" for yield from.l.l g (15.5 mmol) ot'tn(phcnyl-1-r/)phosphineand 0.7() l-l hr. Hcre, isotopiccompositions of the biphenylderivatives C Q.7 mmol) of rhodium(ltl) chlondc hydrate according to the rvere:bipherryl (83.6ii clo,11.3% d1, 1.7\ d,, and 0.3'Z dr),2- procedureof Wilkinson:e6 mp 155-157'1li1.oo mp for an undeu- bromobiphenyl(52.5 \ tl,, 38.8% dt. 7.8-- 4, and 0.8'Z d), and teratedsample 157-158 '). 2.2'-dibromobiphenyl(71.9% dl. 26.7% c/r.and :.37i (lr). Decomposition of ltethy'ltrisItri(pheny'l-2-r/)phosphine]rhodium(I). Biphenyl-2-r/1,biphenl'l-3-r/1, and biphenyl-.1-tl1were preparedby Methyltris[tril phenyl-2-r0phosp h r rre] rhod i u m( [), preparedfrom 0. 50 reactionof the correspondingGrignard reagentsrvith deuterium g of tris[tri(phenyl-2-r|phosphine]rhodiurn( I) chloride according to oxidein THF solution.and rverepurified by crystallizationfollowed the procedureof Keim.{7was heetedfor.l hr at 120'. The methane b-v'sublimation. llclting points and massspccrroscopic isotopic evolved. after having been passcd over alumina to remove traces compositionsof each isomer were: biphenyl-2-r/.mp 69-70o, of residual ether, was analyzed lbr deuterium by mass spectroscopy. 92.1'\ 4, 7.47ido; biphenyl-3-d.mp 68.5-69.5'.62.4'Z du 37.67f, The methane lvas shown to contain 8l .-1% CHr and 18.7% CHrD, d,,: biphenvl-.1-rl.mp 69.5-70",88.0:; r/r, ll.0'i dr. Ir spectra giving. after correction lor undeuteratedphenyl groups in the tri- plrenylphosphineligand, an isotopeetlect ot' kst'ko : 4.2 *.0.1. t9-s)Prepared from bromobenzenc-2.4,6-rli.synthesized using the proccdureof J. Nt. Scarborough,U. S. Atornic EnergyCommission, (96) J. A. Osborn. F. H. Sardine.J. F. \'oung, and G. Wilkinson, NAA-SR-21-1-l( 1957); Chent..4bsn,. 52.9012d ( 1958). J. Chern.Soc. A,lTll (1966).

J, )rtntul ttl lltc .-lrnerictut Clrcttticul .Srrc.iutI ')l l,) Septetttber21 , 1970