Functionalized dihydropyridines do reduce alkoxycarbene complexes of chromium and give access to polycyclic butenolides

Abstract

The dihydropyridine-induced reduction of alkoxycarbene complexes of chromium has been generalized to differently substituted dihydropyridines, e.g. N-benzyl dihydropyridine and N-methyl-N’N’-diethyldihydronicotinamide. In all the cases examined, alkoxyalkynyl carbene complexes lead, upon cascade insertions, to butenolides, the diastereomeric excesses being dependent on the structure of the dihydropyridines.