PREPARATION OF BETA- TRIALKYLSTANNYL- ALPHA,BETA-UNSATURATED CARBONYL COMPOUNDS AND THEIR CONVERSION TO VINYLLITHIUM REAGENTS

The preparation and synthetic utility of various (beta)-trialkylstannyl-(alpha),(beta)-unsaturated carbonyl compounds is described. In this connection, treatment of tetrahydrofuran solutions of Me(,3)SnLi and n-Bu(,3)SnLi with one equivalent of PhSCu led to the in situ formation of PhS(Me(,3)Sn)CuLi 72 and PhS(n-Bu(,3)Sn)CuLi 73, respectively. The latter reagents readily transferred, in a conjugate sense, the trialkylstannyl group to (alpha),(beta)-unsaturated carbonyl systems. In particular, these trialkylstannylcuprate reagents efficiently transformed (beta)-iodo enones 4 into (beta)-trialkylstannyl-(alpha),(beta)-unsaturated ketones 11, a new class of organotin derivatives. Likewise, treatment of the (beta)-iodo enones 4 with Me(,3)SnCu(.)LiBr(.)SMe(,2) 94, prepared by the reaction of Me(,3)SnLi with one equivalent of Me(,2)S(.)CuBr, gave the corresponding (beta)-trimethylstannyl enones in good yield.;The reaction of PhS(Me(,3)Sn)CuLi 72 with various (alpha),(beta)-acetylenic esters is also described. The course of the reaction could be controlled experimentally so as to produce, highly stereoselectively, either the (E)- or the (Z)-(beta)-trimethylstannyl-(alpha),(beta)-unsaturated esters. Treatment (THF, -78(DEGREES)C) of PhS(Me(,3)Sn)CuLi 72 with (alpha),(beta)-acetylenic esters in the presence of a proton source (e.g., MeOH) gave the corresponding (E)-(beta)-trimethylstannyl-(alpha),(beta)-unsaturated esters in good yield. Reaction of 72 with (alpha),(beta)-acetylenic esters at slightly higher temperatures (-48(DEGREES)C) in the absence of a proton source resulted in the formation of the corresponding (Z)-isomers.;Reaction of ethyl (Z)-3-tosyloxyacrylate 180 with Me(,3)SnCu(.)LiBr(.)SMe(,2) 94 and n-Bu(,3)SnCu(.)LiBr(.)SMe(,2) 181 gave the corresponding (Z)-(beta)-trialkylstannylacrylates.;Finally, two of the (beta)-trimethylstannyl esters, ethyl (E)-3-trimethylstannyl-2-butenoate 163 and ethyl (Z)-3-trimethylstannyl-2-butenoate 166, were converted into the geometrically isomeric trimethylstannyl dienes 184 and 185, respectively. Both of these substances underwent rapid and complete transmetalation when treated with 1.2 equivalents of methyllithium in tetrahydrofuran. The resultant 4-lithio-1,3-pentadienes (186, 187) reacted smoothly with a variety of electrophiles to produce the corresponding substituted dienes (192 and 193).;Two of these (beta)-trialkylstannyl enones, 3-trimethylstannyl-2-cyclohexen-1-one 70 and 3-tri-n-butylstannyl-2-cyclohexen-1-one, 74, were transformed into the vinylithium reagent 111. Sequential treatment of the enones 70 and 74 with lithium diisopropylamide and tert-butyldimethylsilyl chloride in the presence of hexamethylphosphoramide gave the enol silyl ethers 110 and 108, respectively. Transmetalation of the compounds 110 and 108 was accomplished by treatment of these substances with 1.1 equivalent of an alkyllithium reagent. Reaction of the resultant vinyllithium reagent 111 with electrophilic reagents proceeded smoothly to afford the corresponding substituted 1,3-cyclohexadienes in good yield.