Síntese de calcogenetos vinílicos a partir de dialquinos ou selenoalquinos

Abstract

In this work, the synthesis of the vinyl chalcogenides starting from dialkynes or selanylalkynes is describe. In the hydrochalcogenation reaction polyethylene glicol-400 was used as solvent and the reducing agent sodium borohydride in the presence of conjugated dialkynes 1a-b and diorganyl dichalcogenides 2a-e to obtain (Z)-1-organylchalcogeno-1,4-diorganylbut-1-en-3-ynes 3a-h, under mild conditions at 30 °C. Moreover, (1Z,3Z)-1,4-bis(organylchalcogeno)-1,4- diphenylbuta-1,3-dienes 4a-c were obtained at higher temperatures. This general and simple method provides the vinyl chalcogenides preferably with Z configuration by using of conventional heating or microwave irradiation. From selenaylalkynes 5a-j was possible to synthesize functionalized imidazole vinyl selenides. The synthesis was carried out by nucleophilic addition of imidazole 6 in additive-free conditions using N,N-dimethylformamide as solvent. This methodology is regio- and stereoselective in getting new vinyl selenides 7a-j exclusively in Z configuration.