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Publication 121  


  1. M.P. Doyle, M. Protopopova, P. Müller, D. Ene, E.A. Shapiro,
    “Effective Uses of Dirhodium(II) Tetrakis[methyl 2-oxopyrrolidine-5(R or S)-carboxylate] for Highly Enantioselective Intermolecular Cyclopropenation Reactions”
    J. Am. Chem. Soc. 1994, 116, 8492-8498.

The title compounds are effective catalysts for intermolecular cyclopropenation reactions of 1-alkynes with diazo esters and diazo amides. Diastereoselectivities achieved from the appropriate match with d- or l-menthyl diazoacetate are 77 to ≥94% de. Enantioselectivities up to ≥94% ee with 3-methoxy-1 -propyne and 3,3-diethoxy-1 -propyne have been obtained. Variations in these values for metal carbene additions to alkynes are associated with electronic and/or steric influences from the alkyne or carbene substituents. N,N-Dimethyldiazoacetamide provides a higher level of enantiocontrol than do diazo esters. The absolute configurations of the cyclopropene products have been established; dirhodium(II) tetrakis [methyl 2-oxopyrrolidine-5(S)-carboxylate], Rh?(5S,-MEPY)?, produces 2-substituted-2-cyclopropene-1-carboxylates having the (S)-configuration whereas use ofRh?(5R-MEPY)? provides these cyclopropene products in the (R)-configuration. Diimide reduction of these cyclopropenecarboxylates produces the cis-disubstituted cyclopropane products exclusively.

DOI : 10.1021/ja00098a009 

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