Heteroorganic betaines 3. Reactions of betaines containing the P+-C-Si-S- fragment

The [Ph3P+-CMe2-SiMe2-SEt]Br- salt was prepared by the reaction of betaine Ph3P+-CMe2SiMeR-S- (1a: R = Me) with EtBr. Acetylation of betaine 1a or Et3 P+-CHMeSiMe2-S- (2a) afforded 2,2,6-trimethyl-1,3-dioxa-2-silacyclohex-5-en e-4-thione Me2SiOC(=S)CH=C(Me)O or the [Et3P+-CHMeSiMe2Cl]Cl- salt dependin g on the reagent ratio. The reactions of betaines la,b (Ib: R = Ph) or 2 wi th compounds (R3Sn)(2)X (X = O or NMe can be used for the generation of sil anones [RMeSi = O] and silaneimines [RMeSi = NMe] in solutions. The reactiv ity of betaines Ph3P+-(CHRSiMeR2)-Si-1-S- (R-1 = H or Me and R: = Me or Ph) is determined by the equilibrium between the zwitterionic and ylide Ph3P = (CRSiMeRSH)-Si-1-S-2 tautomers that exist in solutions.