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Intramolecular Addition Reactions of Aryl Radicals

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Intramolecular Addition Reactions of Aryl Radicals t: .t, .., :, ,,ltt.': ',.:' i,i,: , ì i L::,.- ì I lo1¡.i;t,ri \ \_.f. -.lr_lÌl '\:,^ .'ì;^ ì :lljlT;ì\i .(-l.t j_.1.,1 ,¡r, I'ri-)t-¡T [(_-,,.r jì Ì.ì,c,_l ':]-oij:,j -':-*{.ï^v¡}9t'- (.)ï' ;\ì?.Y L ì,:\ ri-i-í_-.;\J' i :\ .,1- 'r: :r ¿ ì T /a l\ 1 iì1.._!.)r.,) irìì-,tS rii"i'l'ji D ¿¡O;ì :rl;lìi l).JGrìit ,J OI' Di,-r¡-"¡¡,.a C,:r Fli.it-r-)SOPtîY in tl:.-¡ irlli-i:V lR:j-IT'f 0,:¡' j\lfi.r'I-,jÀ-l- D,:,1 by lüIi,L.l:¡ii; .r¡\i,i-il,ll Gi\,?ji, i-ì Íìc (i-:Ons: (.,fCet. " " " ) ) Den¡ir'i:ment of CrrJa ):r j_c Clllr.,lirii s;-brlr 1.97 0 co¡ÏtJ¡:rlts .Page. SU¡TI'JARY (Í) ST,\Tilt.:.lldT (ii) ( j_ií AC F.i'i O i4 J.,lI IJG C T"iE lr'l!.' S ) FTJBI,ICATTOI'{S (iv) tr.qR.T T : TNTRODUCiTTOI{ Clll\L"f,Ír)" l- e .[ntermolecu]ar l\<iclition o'F Free R.acilca.ls; to Olefins i-"1" .Addition of A1Ì<¡r1 llaciicals ancl iLe-lated S¡:ecies L Io2n The Transiti.on State irr l¡ree Radical. Addi-tion ]ìeactions 3 1"3. ho'rJj.t-ì-on of Ar1zl Rac.licals B cIl"\PTlrR 2¿ fntramolecular r\c-'lclitÍon of Free -Radicals to olefins 2 0r, Cycli-zation of lì¡rc-lj-cals Porrited by tr::ee lìadj-cal- Aciclitj-on to iCerrninal Dienes 9 .la ¿-a /-o Cyc1izat.Íon l{eact.i.ons o:Í -Radj.cals F o::med by Abstr¿rction o'î. ð-n Actj.vated }i'qdrogen-í\tom 12 2"3n Cycli-z;a.Lion of À-lJ<yI Ra.dica-1s; Generar¿ecl in the Ài:s;ence of StabilizinçJ l¡unct-;Loiral GrouÞs 21. 2u4o Cyc-lÍzation of ;\11'.y-t- P'aclicals Generated from A,lJcyi- Ilalides Ï'lt 'Llriallcyl- an<l Triaryl Stanna-nes 3o CÍTJ\PTIIR 3: ilomolvt.i-c rirona-tic SubstituLion 3. 1 o -Lnt^ermolecula-::,à.rolnat'ic Sub- stitutlo:r R.eaetions of ÂrYl :ìadicals 44 3o2o Tutramolecular luo;nat.ic St-r.b- stitution iLea.ct-ions of i\ryJ. RadÍca1s 45 ar'lT:\ l)ii-r i!::) A . iletection of Lailic¿rls bv ]-]-ectron Parallaq'netíc P.e sonance Spect:losco]-)y 4oJ-n Sta.tic Sys'bens 4€, 4020 The --Florv 'I'echniqur.e 50 P.l\:ìT f l: : RESUí.TS AiiÐ Dl-5Ct,rs.SÏCi.;I Cli.i\l:T'il,:l 5 c O]3J:TCTT \¡ìS 51 5.f , lllectron Peira.tna.gneti-c .Resonance Stuci-ie U = " 5,2, r1><plor:atory Pro<iuc'b Stuclj-es of ,\ryl R.acl:i.ca-1 Cycliza{:J"on :?.eact:Lotr e 62. 5.3. Synthetic !'/o:lk (a ) Prea-mble 67 (b) Syntheses of hrYl fodicles .:.ncl thei-r Possible R.echrct'.ion Prorju.cts 6!] (c) Syntheses of iVnines for E -l-e ctrot: Pa-ra¡nagnet i-c P.esonance Sturlj-es 75 5.4o Aryl lìadicerl C-ycllzat.ion Reaetic¡::s Ì:y the iìedr-lction of ;\ryl lodicles wi'i:h fr ibu.tvl st,annane BO 5o5n Conclu-s:ions LO4 PAR'T T.r-T : N.çP¡iAJ:i',l]'IÍTAI, Cl:iAliT.-riR 6 ¿ 6"Lo Preamble 118 6,2 0 Frepal:ation of l\r-y-l Iodicies and their lJxpected Products from the T'.r i -n -butyI stannane Rr: clrrc't i ons r22 6030 Slznt-heses of ,lu-nj-nes ancl of thei-.r Respective Diazoníum Sa-lts for El-ectron Paramagnetic -Resonance: Str-rdies Is2 6 ,4, Iìecorciing of Lhe Elec'tron Paramagnetic iìeÊionance Spectra 1.62 6.50 Reductions of o-¿\11yJ-o,.<ybenzene- diazonium ¡o::of l-u.oride with Va_ric¡us Reducing l\gents 163 606. lìeductions of .Aryl lodides with TrÍ-g-butylstannane I67 F.-NìT :tV : REh',:liì.TI.,iC]lS 184 (i) SìJÌ,!i'r-i\i.:f l,re ha'v-e de¡nonstra.tecl that in'tr¡trnolecul¿r.r cycliza.t.ion reac'tions of a-ryl radical-s, 'witìr ortho su.lcstitu-ents containing C=C dor:bl.e J:onds :ln the 5-6 or 6-7 pos-i-tion relative t.o the rac.lical centl:e, occur v¡ith qreafl ease' i'ie have also l¡eeir abl-c.: to confirm that the redur.c-tion of: arryl iocii<ies v¡ith trj--n-l:utylst,anna-ne proceecìs by a radical mechani.gm. From ¿rccu.rate t:rocìuct stuclies \¡/e tJere able t.o cst.im¿rt'.e o'f the rate cons.tantFj - t-hese aryl radícal cyclÍzation reac-tj-ons, and to esta-blish that siuch intrarnolecuLar rÌng elosrrre reac'tions occul: by radícal a'btacl< at that end of the terrninal C=C bond ¡¡¡irj-ch is nearer to the beirzene ::inq. i{e have a.lso beet: able to estirnate the ratq constairts of tvro j-ntrarnolecuLar 1'rydrogen-atom al:sEraction reactions of aryl ::adicalså those probably consti'trrte the only cluantil-clbive d¿tta availal:le for such reactions. þ'ur'bhermore by electron s,oin l:esonance inves'L.igations vze have observed the specLra clue t'o the cyclic raclical intermedia'tes of intra.molecular aryl- radical cyclization reactions n (i-i) STi\T'lli'iiJI'lT This t-.hes:Ls cont.ains no mð-tel:ia1 prev:Lotlsl.¿ subini-tt.ecl for a cìegree or d-iplorna in any LTnivêrsi-ty, ancì to the besL. of rny J.,nov¡leclge ¿rncl l¡elj-ef , conLa-ins; no ¡n¿rteria-L previou.sly publ-íshed or v/rit,ten by arnother personr e>:cept v¡l-lere due referencr: is m¿rcie in tl-le te>ct. I,y'ïl,l,T;.\).n' li. GARÀ (iii) I\CI(IiI oi.,f LE D:iDì lill'riT's I wish to e:;press my gra-t'i-tucle to Professor Ao 'l'. J. Beci<v¿i-th for hÍs encor-lragement clurinq the supervision of this lvorlço f al.so i+ish to tha.uk Dr, G. E. Gream for the interest wllich he has Laken i-n this r^/orko I thanl< the Com¡rouwealth of Australi-a for a Post-Graclua'Le At^¡ard v¡hich made this work Possible" ( iv) PUß.LICATIOI:lS Part of this lvorl< has beetr pu-blished in the f oll-ov¡ing colnmunications; - l\. L. J. Becl<v¡ith and trt. B, Garar J. Amer. Chem. Soc. ¡ 4!., 5689 (1e6e) A. L. il-. Bec]<v¡ith and I,V. B' Garar Jo ,Arnero Chem" Soco , 2L, 5691 (1959) (see at the b¿ick) PAP.T Ï Tlí l'[ fì Ll ]l)ti c T I o]T CHAPTER 1 TNIERMCLECULA|I. ADDITÏ ON OF FREE RI\DTCALS TO OLEFII{S -r- }.1. ADDTTIO}I Oii I\I,ITVI, PTÄ.I)ÏCA'LS .\iJD RET,,J\T]ID SPECÏAS This to¡:ic will be consj-dered bri<-:fly in o::der that' it may be contrasjted Ia'ber wit.h analoqous intrarnolecular reac'tionsn In particular,the niain point of lrrte:rest v¡ill be the direction of addition of a-Lkyl raclicals to unsymrnetrical.ly substituted olefins. Pj-oneerinq worJ< by l'.ha-ra.sch and hls school established that good yfelds of mononeric adducts are obtained when hycìrogen 'l bronri-dert carbon tetrachlorldeno_1_2_ chloroform- and va.rious alclehyctes" are allo'wed t.o react wlth olefins in the presenc:e of radÍc¿rl- inítiators" In each case, they p:lr-rpcsed a radj"cal chait: rnechanism to aecour¡t for the observec.i proCucts. The suggested mechanisn f or this.. bype of reaction involves init-ial attack by the radical at the less h:'-ghly substituted end of the clouble bond to f orm an intermediate radical adduct r r,r'hich 1s converted to a stable product by rardical chain tr'ansfer with a molecul.e of the addend" 4 lniore recerrtly i{eyo Cado-qan and their co-worl<ers f out¡d that active meth-ylene compouud$ Stlch as mal-oníc, acetoacetic and cyanoacetic esters add t-o olefins in t.he presence of radical in.itiators gÍ.ving mono¡'¡rerÍ.c adducts in good yields" The analogop.s radical-in.i-tiated adciition react.ions of perfluoroa-tlcyl íodicles to olefÍns rnrere examined itr de'bail by Ha.szeldine a¡:d hj-s gto,rp.5 ïn 1957 }l¿rszeLdine arld Stee.le6 -2- reporeed that a mÍxtrrre of the trnzo possible ad<lucts obtaj-ned from the racllc¿rl reactions of both trif.Iuoromethyl Íodide and hydrogen bromide with trifluoroethyl.ene l'ras¡ rrt'he first example of anythíng other than excluslve or predomj.nant (> 95%) radical or atomic at,tack on one carbon of an unslnnmetrical olefinrr. Their ratlonale for these results was that the two int.ermedtat.e radical adducts, fornred by attack at one or t'he olher end of the double bond of trÍf luoroethylene r \^7ere of slmilar thermodlmamic stabllit,y. on this basis nelther mode of att.aclc woukl predomlnate i horvever thj-s was in conLrast i¡¡ith observati.ons for other olef íns.6 TÌre work descrÍbed above documents the staternent thatt in general, intermolecular radlcal additions to C=C double bonds proceed prçdominantly or exc.lusj-vely via the thermo- dynamlcally rnore stable of the two possible iutermedÍate radÍcal adciucts.
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