Hydrotrispyrazolylborate-copper complexes as catalysts for the styrene cyclopropanation reaction with ethyl diazoacetate under homogeneous and heterogeneous conditions

A series of complexes of general formulae TpxCu have been employed as the catalyst for the styrene cyclopropanation reaction with ethyl diazoacetate, both under homogeneous and heterogeneous conditions. Several solid supports have been tested, with silica gel being the most convenient for this transformation. A comparison of the results obtained under both conditions has shown that the catalytic pocket is affected by the support.

Graphical abstractThe TpxCu complexes efficiently catalyze the cyclopropanation of styrene with EDA in high to very high yields both in homo- and heterogeneous conditions. The diastereoselectivity toward the cis-isomer is decreased when moving from the latter to the former conditions, revealing a distortion of the catalytic pocket.Figure optionsDownload full-size imageDownload as PowerPoint slide