title: Asymmetric catalysis on the intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones.
abstract: This work describes the development of a highly enantioselective asymmetric catalysis on the intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones. We have found that the catalytic asymmetric intramolecular reactions of alpha-diazo-beta-keto sulfones generally proceed with high enantioselectivity when the alpha-diazo-beta-keto mesityl sulfone is used with the newly prepared ligand 2e. The absolute configuration of products has been determined by X-ray crystallographic analysis, and the outcome of the enantioselectivities is explained well by our proposed models A and B. The products possess great potential for natural product synthesis because (1) many different chemistries of cyclopropane, ketone, and sulfone are available, and (2) the products are generally highly crystalline, facilitating the supplies of enantiomerically pure synthetic intermediates.
authors.affiliation: Department of Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Honma
authors.forename: Takashi
authors.initials: T
authors.lastname: Sawada
authors.forename: Yuri
authors.initials: Y
authors.lastname: Fujisawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Utsugi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Akinori
authors.initials: A
authors.lastname: Umino
authors.forename: Takehiko
authors.initials: T
authors.lastname: Matsumura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hagihara
authors.forename: Masashi
authors.initials: M
authors.lastname: Takano
authors.forename: Masahisa
authors.initials: M
authors.lastname: Nakada