Synthesis of 2-alkoxycarbonyl enamino thioaldehydes and selenaldehydes (as pentacarbonyltungsten(0) complexes). Improved synthesis of simple and 2-cyano enamino thioaldehydes and some chemical reactions of these compounds

Abstract

A series of stable 2-alkoxycarbonyl enamino thioaldehydes (2a–g) were synthesized by solvolysis of the Vilsmeier salts (1) with aqueous or methanolic sodium hydrogen sulphide.

Three 2-alkoxycarbonyl enamino selenaldehydes were obtained as the pentacarbonyltungsten(0) complexes (7a–c). The 2-cyano and simple enamino thioaldehydes (3a–m) and (6a–j)(including some new homologues obtained by an improved synthetic method) are described. Some reactions of 2-cyano and 2-alkoxycarbonyl enamino thioaldehydes were examined e.g. oxidation with MCPBA to give the isothiazoles (8). The symmetrically tetrasubstituted pyridines (9) were produced by bimolecular cyclisation under acidic conditions: hydrolysis in acidic 95% aq. EtOH gave the enamino aldehydes (11) and aroylacetonitriles (12) together with (9). The imines (13) were formed in good yield on reaction with primary amines.