A Novel 3,4-Bis(sulfenyl)- or 4-Selenenyl-3-sulfenylpenta-2,4-dienylation of Aldehydes Using 4-Alkoxy-1,2-bis(sulfenyl)- or 1-selenenyl-2-sulfenylbuta-1,3-dienyl Lithiums

Abstract

3,4-Dichalcogenopenta-2,4-dienylation of aldehydes proceeded in good to high yields using 4-ethoxy-1-(benzenesulfenyl)-2-(methylsulfenyl)- (1), 4-ethoxy-1,2-bis(benzenesulfenyl)but-1,3-diene (2), and 1-selenenyl derivatives 3 and 4 by a two step procedure: i) the reaction of 4-alkoxybuta-1,3-dienyl lithiums with aldehydes; ii) hydrolysis of the penta-2,4-dienyl alcohols with SOCl₂/pyridine. This novel four-carbon homologation could be applied to a tandem reaction of pivaldehyde to give 3,4,7,8-tetrakis(benzenesulfenyl)-10,10-dimethylundeca- 2,4,6,8-tetraenal (15). 3,4-Bis(phenylsulfenyl)penta-2,4-dienals underwent intramolecular cyclization with a catalytic amount of p-toluenesulfonic acid to afford the 3,4-bis(phenylsulfenyl)cyclopentenones 18a,b in moderate to good yields.