Thiosemicarbazone copper complexes as competent catalysts for olefin cyclopropanations

New copper complexes of several thiosemicarbazones have been prepared and characterized. All complexes have been prepared by employing Cu (II) acetate hydrate, but analytical and spectroscopical data for the isolated complexes revealed that in most cases a reduction to copper (I) occurred. Cyclopropanation reactions of several olefins by ethyldiazoacetate (EDA) in the presence of catalytic amounts of the complexes were examined. The reported results showed that all complexes are competent catalysts for the cyclopropanation reaction of unactivated olefins. Cyclopropanes were obtained in high yields (up to 97%, TON up to 18,400) with moderate to excellent diastereoselectivities (up to >99%). (C) 2012 Elsevier B. V. All rights reserved.