Site selectivity in the rhodium(II)-catalyzed reaction of α-diazoimides. Ligand and substituent effects
作者:Michael Prein、Peter J. Manley、Albert Padwa
DOI:10.1016/s0040-4020(97)00479-1
日期:1997.6
The product distribution obtained from Rh(II)-catalyzed decomposition of alpha-diazoimides derived from glycine methyl ester has been found to be selectively controlled by the proper choice of catalyst. When the reaction was carried out using perfluorinated ligands, the diazoimide cyclized to produce an isomunchnone dipole whose formation could be monitored by NMR spectroscopy. Reaction of the dipole with a trapping agent such as N-phenylmaleimide resulted in the isolation of a 1,3-dipolar cycloadduct in high yield. The product distribution changed dramatically when rhodium(II)-acetate was employed as the catalyst. The products obtained from this reaction were derived from an azabicyclic epoxide intermediate. The catalyst effect can be modulated by the addition of Sc(OTf)(3) as a Lewis acid or by using nitromethane as the solvent. Changing the nature of the interacting carbonyl group had little effect on the cyclization pathways. (C) 1997 Elsevier Science Ltd.