motel l tabillred earbonol4e underso l ffectfw remztloom rlth l 1km.o to (r*norxto cycloprop*n*~.~ Whom the 1ntowdlxtoo or* l pproprletoly stxbiltzed. havor. other rrxctloa pathway* lnvolvln# dlpoler 1ntomodlat*x .r. poorlblo. Many 01 Chooo procooxox xro xyothetlcxlly ux*fuI and lncludo a oarleo of 2 l 3 cycloaddltlonx botwwn rarltlplo bonds and carboaolds derived trcu diarocatboclyls. Such reaetlons re8ult in the formation of dthydroiurono froa *lay1 l thoro,' dloxolos from rldoydoo3 and oxexoloe frarP nltrlloo. ' Both the rlw-openlog roactloo botroon luranx and carbonoldo to ~onorato d1rn.r' and the xlkylotlon of pyrroloe by carboaolda* alxo appear to lnrolv dlpolxr lntormodlatoa. The octuol l trueture'of the dipolor intomodl~t~ In many of those reaction8 la open to dobat.' bocxuoo l ubtlo quootlono such l @ the role of the notal, or the rolatlvo rate. ol bond Corwtlon are dlfflcult to l oowor. Proviou8 studlox hove shorn that rhodlrP(II) acat&* cotolyzod dwxmpoaltion oi ethyl dloxoocoteto in the presmcm of ~c~tylm~s Ia l rieble method for the l yntheolo of cyclopropraoo. * Introductloa of wltablo !unctlonallty to l tabllltr l dlpolar lntorwdlrto H. M L. DAVB rod K. R.
Rowsa compounda wsrm carried out in th. pr...nc. of l lkylwotyluwm. but thoao roactlons dld not rssult in th. fomstlon of fursns. Vlth t.rrln.1 .cstyl.oss, cyc10pr09.n.. wsr. tomsd in ylslds rm61.6 Craa M-611 (T.bls 1, sntrlss I-3). but .o products dsrlvsd from cl... c.pturs of th. c.rbsnold vsrs lrol.bl. In ths rsactloa rlth 3-hsxps (ontry 6). Prenumrbly, this su(;~sst~ thst l tsrlc sftsctm l rs ioportmt in dst.rmlol.6 rhothor or not ths cwbsnold 1nt.msdl.t. c.. b. .rflc~.otl~ trappad. rurtherpors. l n tort-butylacettlrns rsaccsd .if.ctlv*ly (**try 3). it would sppsrr that it 1. nscs...ry for only ons end of th. .c.tyl.n. to b. r..dlly .cc...ibl.. CH3 CH3 0 )c-Y r. x -CHJ. Y -COCM3 X @ x -CHJ. r -COOEC N2 & X-O&. Y -COOEt 0 a g X-OEC, Y -CH-CHCOOtt R2 2 A second approach Co sohwcs . dlpo1.r latsrmodI.tx would b. to introduc. slsctron don.tf.6 6roups ooto ths scstylsns. 6.s.d on this l xp.~t.tloa. th. rhodlum(lf) .c.t.t. c.t.lyrsd d.compo.ltloos ol I.-d wsrs csrrlsd out u.l.6 ph.ny1.csty1.n. . . tr.ppkn6 .&sat. fhs rssult. of thlm .sri.. ol sxpsrimsnts l howd l rsorrkabls dspmdanca on ths ..turs of ths .i.ctro. rlthdrsela6 'roups 01) ths c.rbsnold f.ntri.s 5-6). Vitb dlsthyl dl.+ca.lon.t* c&j. th. cyclopropsas 3~ w.s fomsd, but vlch 3-dlaro-2.4-pentanedlone C&I. tha furan $= was the 001~ product. Ths awater CmAdenCy for a kstone carbon?1 rathsr than SD emcsr csrbonyl to uodsr6o ring closurs to l rurm 18 nlc.ly Illustrstsd In the r..ctlon with *thy1 di~toae~toac~tat~ (e). rhlch t.bl. I Rhodlum(II) Ac.t.t. C.t.1yr.d D.coepooItlo. of I.-d tn the Pr...nc. of Ac.tTl*a*s WTRT ACIRLQR DIAL0 Cm