Facile Synthesis of Furowarfarins via Hetero-Diels–Alder Cycloaddition Reaction

Abstract

Synthesis of new furowarfarins has been carried out via tandem Knoevenagel–hetero-Diels–Alder cycloaddition reaction. One-pot, multicomponent reaction involving, heating a mixture of hydroxy chromenone, aldehyde, and 2-methoxy propene afforded pyranochromenone with good diastereoselectivity, favoring the exo (trans) cycloadduct, in contrast to previous literature reports. The pyran ring exists in a half-chair conformation with C9-OMe in ψ-axial and C7-phenyl ring in ψ-equatorial positions. Single-crystal x-ray analysis conclusively confirms the structure.