192. P. Müller, Y.F. Allenbach, S. Chappellet, A. Ghanem,
     “Asymmetric cyclopropanations and cycloadditions of dioxocarbenes”
     Synthesis 2006, 1689-1696.

Methods for enantioselective transfer of carbenes starting from precursors carrying two carbonyl groups have been elaborated. A one-pot procedure for olefin cyclopropanation with CH-acidic precursors via intermediate phenyliodonium ylides has been developed. The structure of the [Rh₂{(S)-nttl}₄] catalyst was optimized to produce up to 98% ee in olefin cyclopropanations with dimethyl malonate or Meldrum's acid. Highly selective Rh(II)-catalyzed olefin cyclopropanations could be observed upon replacement of methyl diazoacetoacetate by methyl (silyloxy­-vinyl)diazoacetate. Enantioselective dipolar cycloadditions of diazo­pyruvate to polar olefins have been realized with Ru(II)-pybox catalysts.

DOI : 10.1055/s-2006-926452 

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