摘要:
Synthesis of new furowarfarins has been carried out via tandem Knoevenagelhetero-DielsAlder 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 ?-axial and C7-phenyl ring in ?-equatorial positions. Single-crystal x-ray analysis conclusively confirms the structure.