Kinetic acidity of iminium ions. 2-Alkynyl- and 2,5-dialkynyl-pyrrolidines via the iminium ion route to azomethine ylides

Article abstract of DOI:10.1016/S0040-4020(02)00129-1

Condensation of carboxaldehydes with appropriate secondary propargylamines furnishes iminium ions which undergo regioselective deprotonation at the propargylic methylene group to generate azomethine ylides. Interception of the latter by N-methyl or N-phenyl maleimide furnishes 2- and 2,5-dialkynyl-pyrrolidines.