Ring transformations in reactions of heterocyclic halogeno compounds with nucleophiles (XXVI): A 15N‐ and 14C‐study of the conversion of chloropyrazine into imidazole with potassium amide in liquid ammonia

The mechanism of the conversion of chloropyrazine into imidazole by potassium amide in liquid ammonia has been investigated. It has been proved, using the labelled compounds 2‐chloro‐[1‐15N]pyrazine and 2‐chloro‐[2‐14C]pyrazine, that this ring contraction occurs by a nucleophilic attack of the amide ion on position 3. The synthesis of 2‐chloro‐[2‐14C]pyrazine starting from diethyl malonate labelled in the ethoxycarbonyl group, is described.