Highly enantioselective cyclopropanation of styrenes and diazoacetates catalyzed by 3-oxobutylideneaminatocobalt(II) complexes, part 1. Designs of cobalt complex catalysts and the effects of donating ligands

Taketo Ikeno, Mitsuo Sato, Hiroyuki Sekino, Asae Nishizuka, Tohru Yamada

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Abstract

Highly enantioselective cyclopropanation of styrene derivatives and diazoacetates was effectively catalyzed by reasonably designed 3-oxobutylideneaminatocobalt(II) complexes, whose ligands were prepared from 1,2-dimesitylethyl-enediamine and alkyl 3-oxobutanoates. The steric demand of the diamine unit of the complexes seriously influenced the enantioselectivity, and the ester groups on their side chains somewhat improved the trans-selectivity. Addition of a catalytic amount of N-methylimidazole significantly accelerated the reaction and enhanced the enantioselectivity due to its coordination to the center cobalt atom of the complex as an axial ligand. Alcoholic or aqueous alcoholic solvents were also effective particularly for the cyclopropanation of 1-substituted 1-phenylethylenes to achieve high enantioselectivity in aqueous methanol.

Original languageEnglish
Pages (from-to)2139-2150
Number of pages12
JournalBulletin of the Chemical Society of Japan
Volume74
Issue number11
DOIs
Publication statusPublished - 2001 Jan 1

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ASJC Scopus subject areas

  • Chemistry(all)

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