Formation of free radicals in the vinylation of 2-substituted pyrroles with acetylenes in a KOH-DMSO system
By spin trapping, using 2-methyl-2-nitrosopropane (t-BuNO), the EPR signals of vinyl-tert-butylnitroxyls and spin adducts of t-BuNO with products of the addition of 2-substituted pyrrole radicals to acetylenes were recorded during the vinylation of 2-substituted pyrroles with acetylenes in a KOH-DMSO system. The 2-substituted pyrrole radicals have a high stability, and their EPR spectra were observed directly in the vinylation reactions. It is shown that one-electron transfer processes are involved in vinylation.