Research on unsaturated azole derivatives III. Electrophilic substitution reactions in the 2-ethynylbenzimidazole series

2-Alkynylbenzimidazoles were obtained by alkylation of 2-benzimidazolylacetylenes with alkyl halides in liquid ammonia in the presence of sodium metal. The strong — I effect of the 2-benzimidazolyl group hindered attack of electrophilic reagents in alkylation and hydration reactions of 2-benzimidazolylacetylenes. Condensation of 2-ethynylbenzimidazoles with bromophenylacetylene under the conditions of the Cadiot-Chodkiewicz reaction gives unsymmetrical diynes.