A new preparation method for a variety of stable sulfur ylides is described. Reactions of the Corey-Kim reagent with active methylene compounds having two electron withdrawing groups in the presence of triethylamine afforded stable surfur ylides in satisfactory yields.
Sulfonium ions containing electron-withdrawing substituents are formed by the reactions between sulfonium ylides and suitable electrophiles. Reactivities of these sulfonium ions (MeR\overset+S–CX(CO2Me)2) with nucleophiles (Y−) are investigated. The products found are those of 1) C-attack (MeSR+YCX(CO2Me)2), 2) Me-attack (MeY+RSCX(CO2Me)2) and 3) R-attack (RY+MeSCX(CO2Me)2). When R is (+)-2-octyl and
Sulphonium bismethoxycarbonylmethylides react with acids by a pummerer-type reaction and by nucleophilic substitution on sulphonium salts formed by protonation of the ylides; the product distributions depend on both the ylides and acidity of solvents.
p-toluenesulfonamide gave N-p-toluenesulfonyl-S,S-dimethylsulfilimine 2. The reaction of 1 with carbon acids 3 having active methylene gave stable S-C ylids (exchange of S-N ylid for S-C ylid), while 2 reacted with malonitrile to give S-C ylid only in low yield. Thus, the ylid exchange mechanism based on the equilibrium including the protonated sulfonium salts has been assumed.
Reduction of semipolar sulphur linkages with carbodithioic acids and addition of carbodithioic acids to olefins
作者:S. Oae、T. Yagihara、T. Okabe
DOI:10.1016/s0040-4020(01)93661-0
日期:1972.1
Carbodithioic acids react with trivalent sulphur compounds bearing semipolarlinkages (sulphoxides, sulphonium ylides and sulphilimines), to give the corresponding sulphides and add to olefins to afford dithioesters. The orientation of olefin addition is controlled by the olefin nature. Michael type addition takes place with olefins bearing an electron-withdrawing group α to the double bond while Markownikoff