Allylic dithioacetal as a propene-1,3-zwitterion synthon. Regioselective conversion of C-S bonds in allylic dithioacetals into C-C bonds

Reaction of allylic dithioacetals with organocuprate or organolithium reagent followed by treatment with a variety of alkyl electrophiles gives the corresponding E and Z isomeric mixture of vinyl sulfides in good yield. Further cross coupling with a Grignard reagent in the presence of NiCl2(dppe) affords the corresponding alkylation products in good yield. In general, the Grignard reagent having the same alkyl group as the R-2 substituent in 1 is employed so that the stereochemical problem in coupling products can be lifted.