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Semicorrin metal complexes as enantioselective catalysts. Part 2. Enantioselective cyclopropane formation from olefins with diazo compounds catalyzed by chiral (semicorrinato)copper complexes
Author(s) -
Fritschi Hugo,
Leutenegger Urs,
Pfaltz Andreas
Publication year - 1988
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19880710621
Subject(s) - chemistry , diazo , ethyl diazoacetate , cyclopropane , copper , catalysis , enantioselective synthesis , cyclopropanation , phenylhydrazine , styrene , organic chemistry , medicinal chemistry , polymer chemistry , copolymer , ring (chemistry) , polymer
Copper complexes of chiral, C 2 ‐symmetric semicorrin ligands were found to be efficient catalysts for the cyclopropane formation from olefins with diazo compounds. In the presence of 1 mode‐% 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(I) tert ‐butoxide (Scheme 4) , suggest that the actual catalyst is a [mono(semicorrinato)]copper(I).