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 studies have led to the proposal of a general mechanism for the cyclopropanation reaction with copper catalysts, a 14-e species being responsible of the catalytic step. Heterogeneisation of those complexes on silica gel does not affect their catalytic capabilities under heterogeneous conditions when compared with those in the homogeneous phase.