3,3-Dichloroprop-2-ene iminium salts (vinylogous Viehe salts): A study of their reactivity towards nucleophiles

Article abstract of DOI:10.1055/s-1997-1221

The title compounds 3 react regioselectively at either the 1- or 3- position depending on the reaction partner. Chloro substitution affording new propene iminium salts is preferred e.g. in the reaction with mercaptans (to 10, 11), amines (to 7, 14, 15) and some activated arenes and hetarenes (to 26, 27). Nucleophilic attack at the 1-position providing an allyl or allylidene structure is observed e.g. in the reaction with water (to 41, alcohol (to 6), trialkyl phosphite (to 21, 22), trimethylsilyl cyanide (to 30), Grignard reagents (to 31), and acceptor activated methylene compounds (to 33-44). Reaction at both positions with heterocyclization to 13 occurs with thioamide functions. The regiochemistry depends on a complex interplay of several factors in contrast to the FMO predicted orientation. The utility of 3 and some consecutive products as versatile C₃-building blocks for further syntheses is foreseeable.