A. Grinev, A. Chizhov, T. Vlasova
Jun 1, 1977
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Journal
Chemistry of Heterocyclic Compounds
Abstract
Two compounds — the diethylamides of 1,2-dimethyl-3-carbethoxy-6-carboxyfuro[2,3-f]- and 1,2-dimethyl-3-carbethoxy-5-carboxvfuro[3,2-e]indoles — are formed in the reaction of 1,2-dimethyl-3-carbethoxy-5-hydroxyacetic acid (I) with dimethylformamide and phosphorus oxychloride as a result of subsequent intramolecular cyclization of the intermediates. This constitutes evidence for formylation of the starting acid in the 6 and 4 positions. Formylation of the ethyl ester of acid I gives only the 6-formyl derivative, the intramolecular cyclization of which under the influence of sodium ethoxide gives 1,2-dimethyl-3,6-dicarbethoxyfuro[2,3-f]-indole. Hydrolysis of the latter with alcoholic alkali gives the corresponding dicarboxylic acid. The structures of the synthesized compounds were confirmed by the PMR, IR, and mass spectra.