文档介绍：HELVETICACHIMICA ACTA (1988) 1553
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169. Semicorrin Metal Complexes as Enantioselective Catalysts
Part 2
Enantioselective Cyclopropane Formation from Olefins with Diazo Compounds
Catalyzed by Chiral (Semicorrinato)copper Complexes')
by Hugo Fritschi, Urs Leutenegger, and Andreas Pfaltz*
Laboratorium fur Organische Chemie, Eidgenossische Technische Hochschule, ETH-Zentrum, CH-8092 Zurich
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Copper complexes of chiral, C2-symmetric semicorrin ligands were found to be efficient catalysts for the
cyclopropane formation from olefins with diazo compounds. In the presence of 1 mol-% of catalyst, alkyl
diazoacetates reacted smoothly with terminal olefins such as styrene, butadiene, and 1-heptene to give the
corresponding optically active cyclopropanecarboxylic-acid derivatives (Table 1, Scheme 2). With one of the
catalysts, enantioselectivities up to 97% ee were obtained (Table 2). Usually, the reactions were carried out using
bis(semicorrinato)copper(II) complexes as precatalysts. In order to produce active catalysts, these complexes had
to be activated first by heating in the presence of diazoacetate or by treatment with phenylhydrazine. Experiments
with (semicorrinato)copper(I) complexes, prepared in situ from copper(1) fert-butoxide (Scheme 4), suggest that
the actual catalyst is a [mono(semicorrinato)]copper(I).
Introduction. - In the preceding communication [2], we have introduced chiral 1,9-
disubstituted semicorrins 1 as ligands for enantioselective control of metal-catalyzed
reactions. Here we report the first application for this class of ligands, the cyclopropane
formation from olefins with diazo c