N-Vinylation of Imidazole and Benzimidazole with a Paramagnetic Vinyl Bromide

An N-vinylation of imidazole and benzimidazole with a paramagnetic vinyl bromide was investigated. Among the tested procedures, Pd-catalyzed reaction was the most powerful one. The N-vinylation of 2-aminobenzimidazole with a β-bromo-α,β-unsaturated pyrroline nitroxide aldehyde offered 1,1,3,3-tetramethyl-1H-benzimidazo[1,2-a]pyrrolo[3,4-e]pyrimidin-2(3H)-yloxyl radical and the corresponding non-cyclized Schiff base. The reaction of a β-bromo-α,β-unsaturated pyrroline nitroxide aldehyde with imidazole gave β-imidazo-α,β-unsaturated pyrroline nitroxide aldehyde, which was reduced to the alcohol and converted to an unstable allyl chloride.