The use of polypyrazolylborate copper(I) complexes as catalysts in the conversion of olefins into cyclopropanes, aziridines and epoxides and alkynes into cyclopropenes

Polypyrazolylborate complexes of Cu(I) present catalytic activities towards the carbene, nitrene and oxo transfer reactions to unsaturated substrates to form cyclopropanes, cyclopropenes, aziridines and epoxides. Kinetic stud ies have led to the proposal of a general mechanism for the cyclopropanatio n reaction with copper catalysts, a 14-e species being responsible of the c atalytic step. Heterogeneisation of those complexes on silica gel does not affect their catalytic capabilities under heterogeneous conditions when com pared with those in the homogeneous phase. (C) 2001 Elsevier Science B.V. A ll rights reserved.