H. Rudler et al., Reaction of N-methyldihydropyridines with alkoxycarbene complexes of chromium and tungsten: sequential use of three carbonyl ligands of Cr(CO)(6) forthe formation of polyoxygenated compounds, CHEM COMMUN, (15), 1999, pp. 1439-1440
N-methylpyridinium ylide complexes obtained from alkoxycarbene complexes of
chromium and N-methyldihydropyridines easily insert successively a CO liga
nd to give alpha-alkoxy chromium acyl complexes, then a tethered triple bon
d and two additional CO groups to yield bicyclic butenolides.