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Ate Complexes Frorn Diastereomeric Anci Enantiomeric Alkylmercury

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Ate Complexes Frorn Diastereomeric Anci Enantiomeric Alkylmercury . , .t[*p.inted from the Journal of the American Chemical Societ-v-,96, 4937(1gT1).1 Uopyright 1974by the American Chemical Societv and reprinted by permissionof the .opf iight owner. GenerationanC Utiiization of Copper(I) Ate Complexesfrorn Diastereomericanci EnantiomericAlkylmercury Reagentsl David E. Bergbreiter2 and George M. Whitesides* Cotttributiott .frotn thc Dcpot'lrncttt of' Chenti.strl'^Mrissoc.husens Instirrrrc of Teclutttlog.t'.Cambridga. Mu.ssctcimseu.g02 t3A. Recaited F'ebruury ll. l97l Abstract: Treatmentof alkylmercurichalides in successronwith I eclLrivof iodo(tri-n-birtylphosphine)copper(l) -7E-'in ancl3 eclltivof rcrt-bttlyllithiLrmat letrahytlrofumnrcsLrlts in formarion of , r.,,.riu. atc contprlexwhich incorporatcs thc alk-v-igrourp originalll'Lronclccl to nrercurv. Thc reactionsof this alkyl group rcsenrblcthose of a lithiLrmclialkylcr,rpratc: it can be alkylateclwith alkyl halic'lesancl couplccl with a rcir-bLrt-ylmoiety by oridation with nitrobenzene:it does not. however.Ltncic'rgo coniLrgate aclclitions to rr.iJ-unsaturateclketones. In certain instanccs.btrt not aiways.the overaliconversion fronr alkl'lnrcrcrrrichalitlc 1o product takesplacc with retention of configLrrationat the carbon originally bonclciito ntercur.y..The structure(s)of theseate compleres czrnnotbe establisheclfroni the availabletlata, bLrtclLralitatire eviclcncc sLlggests that lithiurm.copper(l). ancl mercury(ll) are all present in the tnetalcore. Possibleapplications anil linritationsof thesccorn;rlcxe.s in synthesis are brieflyolr- lined. Th. inversiorrof stereochenristrythat charactcrizcs the specialinstances in rvhichthey have beenprepared, I SN2displacentent at carbonis the basisfor many only onc ol- tric-rdiasterconicrs has bcen obtained.i, important nrethods of controlling stereochemist.yin Indced.crc-n if it ucrc possibleto generatediastereo- organic synthesis(eq 1). In principle, it shoulci bc merically prrrc .rcc'-alkyllithiuntand -magncsium re- possibleto carry out stereoselectivctransfornrations at ngcr-rts,it is not clcar that thcy w,ould be ntorc than carbon usingdiastereomeric carbanions (or their l'unc- marginallysta blc tou ard epirnerization.1-6 tional equivalents)as nuclcophiles(eq 2): tiiescspecics In contrast. diastercorlericallypure or cnriched RL I) rt r) organometallic derivatives of a number of other , tt, R,..V \., metals- particLrlarlyrnercury(II), tin(lV), and lead- - \: l'-f \-('. + :\ r! (lV)--have bcen prcparcdT-eand establishednot to \ _l) R,./' _t\, epirnerizereadily oncc.formed.10 Unfortunately, or- ganornetallic I) derivatiresof thesemetals are only ll,eakly RL t\' R,..-f R''--l n ucleophilicand of Irrlitcd syntheticutility. + )'-X a--v rIl):X The rvork rcportedin this paperu,as directed toward ,CtNIt + rl r ,, ,tt developing R. lL., rnethods for increasingthc nucleophilic would also be usefulin mechanisticstudies. In prac- (5) F. R. Jcrrscrrand I(. L. Naklntal'c,.1..4trrcr. Chcm..Soc.,88.3437 tice, diffrcultiesin generatingand utilizingthe reqLrired 11966);W, H. Glazc rrnclC. \1. Sclnltn,J. Ore. Chcnr.,33,1987 (1968); W. H. Glaze antl C. i\{. Selrni:n,J. Oruonontatul. Cltutt,,ll. P 3 (1968). nucleophilic specieshav'e preventecicomnton Llseof (61 C. M. \\'hitesiclcslincl J. D. Rotrcrts, J. Antu. Cht,ttt..Soc.,87, proceduresbased on this principic. Gencral ntethods 4878 (lt)65); E.;\. Pcchtolcl,D. G. Ariants, lrnc[G. Fraorkcl, .l. Or.e. (1971): for the synthesisof purediastereomers Chott.,36, 136,S C_'.Frrrcnkcl, C. E. C'rlrrrcll,uncl D. l. Dix, of organorithiunl .1. .ltrtcr. Cht'nt..\or'.,93. 170-1( l97l), anclrcfcrutccs in cach. 1,indl (7) and magnesiumspecies iire not availablc.;r evenin F. R..lcrrsrrrr lrncl B. Ricktrorn, "Elcctrophilic SrrLrstitLrtion of Orglrnorncrcurilrls."McGnrrr-Hill, Ncu York, N. Y., 1968. (l) SLrlllltlrtcc[ _ ill lrart by thc;National Scierrcc Fourtr-lrrtit'rtr,Criutt-s (8) D. S. Nllrttcson,Orltuttontctul. Cltt'ttt. Rr,r'., Sr.c/. .j,4,263 (i969): GP-28586X ancl GP-14247, antl br rhc IntcrnrLrionulCoirr.cr Rcsclrch D. I)oricluncl N{. S. Johnstrn,(hctrt. Cotrttrttrtt.,STl, l37l (1971): G. S. Associ:rtiorr. Ir.ocrrncr,M. l-. Hrrll, lrrrilJ. G. Traylor, .1..lnrar. Cht,m.^9oc.,94, j205 (2) Tcxaco Prccioctoral Fcllou.. 1971 19i'3. (1972): H. G. [iuii ilrr, J. L. Considinc, ancl J. D. Iieurrctl-v,ibirt.,94, (3) H. M. Waltrorskl, yourtg,.1 F. J. intl.listatt),trnrl A. E. ..1rttcr. 7106(lt)71): O. A. Rcutor, ct al., Zlt. Ors. Khim.,5, l9 (1969)fChem. Clrcnr.soc..86,3183 (19(r4); H. i-. Gocring ancrF. It. \,rccrirron. ibiri.. .-1itsrr.,70.87919b i1969)J. F. R. Jcrrson,J. J. l\,lillcr,S. J. Cristol, aircl 80. ll8; (l()58), ilnrlrelrrelter's irr c.;r.it R. S. Bccklct,.l. Org. C'hertt.,37.:13.+l(l9l:t. ('1) Rcccnt stttclicsof tl.rcn'tcchanisnr of cour,crsiorr of ail<11bronriclr.s (9) G. Ni. \\'hitcsirlcsairci .f. Sitrr Filippo, .1r.,.1..4nter. Chcnt. Soc., to alk,r'inragncsiLrnr -lithiiirrl lnrl rcugcltts bf i..lrctiorr rvitir rrretrriinri i_ 92, 6611(1 970); C'. L. Hill anclC. l\I. \\'hitcsitles,ibirl., 96, 870 (1911). catc thal sl.ccics rcsctnirlittga rutlicll lrl utalrv of its irropcrtics1re r;1cr- ( l0) AlthoLrghlrlk5lnrcrcr-rric rcugcnt\ arc strririctou urclcpinrcrizltiolr ntcclilitcsin thcsc rcactions: <"/.H. \4. wllborskl, lrirrl l\i. S. Arorroll-" r)llcc irrcllltrccl,tlttr rl$ tl crpe ricncc ltncl lr prir,'lttccornrl1trrtication frortr i. Orgurrottrctal. C-hcnr.,5i, 3l il97-l): ti. \4. WlrlborsL). linrl Ni. S. F. lt. Jcnscn l"lrs cnrgrhrsrzecithc possibilitl of thcir cpinrcrization in Aronoll-, (1q73). ibid.,5l . 55 Fi \\'. li. J. IJocieriirz,C. Rlonrbcrg. antl solLttion rlurirrg rccr) stilllizutiorr or chronratogral.rhy. This clrinrerizlL- F. Bickclhaupt, T'ctrthcrlrott,29.7l9 (1S73): R .l Koqcrs. H, L. tlort ilppilrcntlr rcllcets a raclicul chairt rcaction initiatccl by sntall Mitchcll, Y. Fujirvara, a'cl \\/hiresirlcs, C. N,t. .i. Org. tlttlrrt." "lg, E57 arlloLUlts ol irer<tritlcs Irrcscnt irr soll'cnts Or fbrnrccl on crltosurc of (1974). itl k1'lnrcrcu r.\'cont I)o u n cls to o r:r'gcit. t Bar,qbreiter, Il'hituirlt's Coppt'r(l) ,,1te (rtntple,res f'ront Alltt'lntercur1' Reagents 4938 with Scheme I. Organomercury Compounds erdo-l and exo-l Are Converted to a Copper Ate Complex and to Products High Stereoselectivity +"HgBr endo-l I -78', THF I t. tlcunnur, -78' +| 2. 3(CH1)1CLi,'- rr->\ 3CH3I,-78' 5PhNO2 ------------* ALH <- H I ,+"* 7004 - 45% C'Hr c(cHr)r <95% endo'3 [CuLiHg].(C(CH,)r)3 95%endo'4 endo'2 75% exo'3 5/" exo'4 N N /l> 1r-H-T -?Ro 5PhNo2 CH, l\ /'\LcrcH ), rl I [CuLiHg]'(C(CH.),), -40% H -70% H I 12/o endo' ) 5% endo-3 H <95% exo'3. excr2 )98/' ext4 1, lICuPBur,-78', THF 2. 3(cH3)3cli, -78o HgBr H exo-l reactivityof one or more of the classesof organometallic exo-2-norbornylmercuricbromide (1) becauselithium substancescapable of yielding diastereomericallyor alkyl(endo-2-norbornyl)cuprateshad previously been enantiomericallypure compounds,while at the same demonstratedto retain stereochemistryat the carbon- time retaining a useful degreeof configurationalsta- metal bond for long periodssf 1lms.t;r'i'1In a typical bility at the carbon-metal bond. Effort has been con- experiment,a tetrahydrofuransolution containing I centratedon attempts to convert diastereomericand mmol of endo-l was treatedwith I equiv of iodo(tri-n- -78o, enantiomc-ricorganomercury compounds into copper(I) butylphosphine)copper(l)at and then with 3.6 ate complexesI I having reactivityt: and configura- mmol of tert-butyllithium. The nature of the organo- tional stabilityr3'r4similar to that of lithium diorgano- metallicspecies present in the resultingsolution has not cuprates. This effort has been partially successful: beendefined in detail: for conveniencewe will referto certain organomercury reagentshave been converted them simply as e.yo- and endo-Z. The representation with useful stereoselectivityinto copper(l) ate com- usedfor 2 in SchemeI, R[CuLiHg]'(C(CHr),)',should plexes having adequatereactivity for use in synthesis. be taken to refer to the composition of the solution Others, however, epimerize partially or completely rather than to the structureof the complex,although during these transformations,or generateate com- qualitativeevidence suggests that all threemetals are in- plexesof low reactivity. Thesestudies suggest correla- corporated into a common cluster in these ate com- tions betweenstructural features in the starting organo- plexes(uide irtfru). mercury reagentsand the syntheticutility of the derived Addition of rnethyl iodide (3 mmol) to the light copper ate complexes,and provide qualitativeinfor- yellow solutionof endo-Z,reaction of the resultingmix- - mation concerninga new and potentiallyvaluable class ture for 30 min at 78", and conventionalwork-up of copperate complexes. yielded 797(, of 2-methylbornane(3, 95% endo, 5% exo)as determinedby glpc analysis;oxidation of endo-Z Results with an excessof nitrobenzeneat -78' yielded-407i' Initial experimentswere carried out using endo' and of endo-2-tert-butylnorbornane(4, 95% endo, 5fl exo). Theseand parallelresults obtained starting with exo-1 (1966): (11) G. Wittig, Qtrart. Rec.,Chem. Soc.,20, 191 W. Tochtcr- are outlined in SchemcI. Neither the yield nor the nrarln,Attgew'. Chent., Ittt. Ed. Ertgl.,5,35l (1966). (12) J. F. Normant, S.trrtftcsis,63(1972); G. H. Posrrcr,Org. Rcctct., stereochemicalpurity of the productsvaried signilicantly 19, 1 (1972); G. Biihr ancl P. Btrrba irr "Mcthodctr tlcr organischcn with the proportions of reagentsused, providcd that Chcmic," 4th ccl, l3 l, E. MLillcr, Ecl., Gcorg Thicrle
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