Benzimidazoles reaction with acetylenic esters

Acetylenic esters add to benzimidazole oxides which behave as 1,3-dipoles the reactions take place vigorously at room temperature. From l-methylbenzimidazole-3-oxide (408) and DMAD, Takahashi and Kano224 obtained 411 via the isoxazoline (409), whereas MP gave 412. The reaction of l,2-dimethylbenzimidazole-3-oxide (414) with DMAD the MP gave the benzimidazolium betaines 415 and 413 respectively ... 

Benzimidazoles, 2,3-dihydro-, by Nu addition at C-2, 56, 203 Benzimidazole, 2-fluoro-, 59, 272 Benzimidazole, 1-methyl-, ring expansion to chloroquinoxalines, 59, 305 Benzimidazole, l-methyl-2-(5 -methyl-2 -thienyl)-, bromination, 57, 319 Benzimidazole 3-oxides, chloro-deoxygenation, 59, 270 Benzimidazoles, 2-perfluoroalkyl-, 60, 25 Benzimidazoles, 2-(l-pyridinio)-, 60, 204 Benzimidazoles, 2-(2-pyridinioethyl)-, elimination reactions, 60, 246 Benzimidazoles, tetrafluoro-, 59, 14 Benzimidazole-2-carboxylic ester 3-oxide, 7-nitro-5-trifluoromethyl-, 60, 17 Benzimidazolium salts, l-amino-3-alkyl-, reaction with activated acetylenes, 56, 138... 

Treatment of 1-methylbenzotrisizole (81) with dimethyl acetylene-dicarboxylate gave the 2 1 adduct 82, which on reduction with stannous chloride in hydrochloric acid gave the pyrrolo compound 83. It has recently been demonstrated that the product from the reaction of the acetylenic ester with the benzimidazole 4 is the pyrroloquinoxalinone 57 ... 

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