Interaction of Dihydropyridines and Nucleophiles with Carbene Complexes of Chromium: Diastereo- and Enantioselective Synthesis of Polycyclic Butenolides
N-methyldihydropyridine with carbene complexes of chromium promotes their spontaneous homologation upon addition of a hydride to the carbene carbon and an insertion of CO. This is followed in the case of complexes tethered to a triple bond by cascade insertions of the triple bond and of a CO ligand giving finally butenolides. The scope of the reaction has been established with its limitations, together