Porphyrin complexes, diastereoselective

W. Adam, V. R. Stegmann, C. R. Saha-Moller, Regio- and Diastereoselective epoxidation of chiral allylic alcohols catalyzed by manganese(salen) and iron (porphyrin) complexes, J. Am. Chem. Soc. 121 (1999) 1879. 

In addition to copper and rhodium catalysts commonly used in the generation of metal carbene complexes, other transition metals have also been explored in the diazo decomposition and subsequent ylide generation.Che and co-workers have recently studied ruthenium porphyrin-catalyzed diazo decomposition and demonstrated a three-component coupling reaction of a-diazo ester with a series of iV-benzylidene imines and alkenes to form functionalized pyrrolidines in excellent diastereoselectivities (Scheme 20). ... 

A review has appeared on the synthesis of enantiomerically enriched aziridines by the addition of nitrenes to alkenes and of carbenes to imines.45 A study of the metal-catalysed aziridination of imines by ethyl diazoacetate found that mam group complexes, early and late transition metal complexes, and rare-earth metal complexes can catalyse the reaction.46 The proposed mechanism did not involve carbene intermediates, the role of the metal being as a Lewis acid to complex the imine lone pah. Ruthenium porphyrins were found to be efficient catalysts for the cyclopropana-tion of styrenes 47 High diastereoselectivities in favour of the //-product were seen but the use of chiral porphyrins gave only low ees. 

The cobalt complexes (9.75) and (9.76) have been used in cyclopropana-tion reactions, but have given poor control of diastereoselectivity, although high enantioselectivities, up to 97% ee with (9.76), have been recorded. In contrast the Co(III)(salen) complex (9.77) provides good diastereocontrol, with reasonable enantioselectivity. Recently, cobalt porphyrins have been shown to exhibit... 

Diastereoselective synthesis of 2-substituted 2E/-chromenes result from metalloradical coupling-cyclization reactions of Al-tosylhydrazones with terminal alkynes mediated by cobalt(II) complexes of porphyrins (14JA1090). Cyclopropenes readily rmdergo a rhodium(III)-catalyzed C-H aaivation with N-phenoxyacetamides to produce 2,2-disubstituted 2H-chromenes in moderate-to-excellent yields (Scheme 16) (14AGE13234). 

---