Heterocyclic mesomeric betaines. Part 3. Synthesis and base-catalysed exchange reactions of N-methyl-5H-pyrrolo[1,2-c]imidazolium iodide

Abstract

Methylation of 5H-pyrrolo[1,2-c]imidazole (10) with methyl iodide gave N-methyl-5H-pyrrolo[1,2-c]imidazolium iodide (11). This salt underwent an unusual base-catalysed exchange of deuterium for hydrogen via a transient dipolar intermediate (9a; Scheme 2). This dipolar intermediate (9a) was trapped with dimethyl acetylenedicarboxylate giving a 2 : 1 adduct (21).