Diastereoselective Synthesis of Spiro[pyrazolone-4,3′-tetrahydrothiophenes] via a Sulfa-Michael/Aldol Domino Reaction

Abstract

A new approach for the diastereoselective synthesis of spiro[pyrazolone-4,3′-tetrahydrothiophenes] was developed. The N,N-diisopropylethylamine-catalyzed reaction of arylidenepyrazolones with in situ generated 2-sulfanylacetaldehyde provides the corresponding spiro-heterocycles via a domino sulfa-Michael/aldol reaction in 42-98% yield and 3:2:1 to 20:1 d.r. under mild reaction conditions.