Base-catalyzed stereoselective synthesis of (Z)-6-arylidenedihydropyrano[2,3-c]pyrazoles via 6-exo-dig oxy-cyclization with pyrazolones and 4-tosyl-1,3-enynes

Abstract

An efficient, straightforward stereoselective synthesis of (Z)-6-arylidenedihydropyrano[2,3-c]pyrazoles is reported by reacting pyrazolones and 4-tosyl-1,3-enynes in the presence of Cs₂CO₃. The reaction proceeds via a formal [3 + 3] cycloaddition involving nucleophilic addition followed by intramolecular 6-exo-dig oxy-cyclization, leading to the title products with the formation of a new C–C and C–O bond. Operationally simplicity, high compatibility and excellent yields are the advantages of this protocol.