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 SOCl
2/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.
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