title: Phase-transfer-catalyzed asymmetric synthesis of axially chiral anilides.
abstract: Catalytic asymmetric synthesis of axially chiral o-iodoanilides and o-tert-butylanilides as useful chiral building blocks was achieved by means of binaphthyl-modified chiral quaternary ammonium-salt-catalyzed N-alkylations under phase-transfer conditions. The synthetic utility of axially chiral products was demonstrated in various transformations. For example, axially chiral N-allyl-o-iodoanilide was transformed to 3-methylindoline by means of radical cyclization with high chirality transfer from axial chirality to C-centered chirality. Furthermore, stereochemical information on axial chirality in o-tert-butylanilides could be used as a template to control the stereochemistry of subsequent transformations. The transition-state structure of the present phase-transfer reaction was discussed on the basis of the X-ray crystal structure of ammonium anilide, which was prepared from binaphthyl-modified chiral ammonium bromide and o-iodoanilide. The chiral tetraalkylammonium bromide as a phase-transfer catalyst recognized the steric difference between the ortho substituents on anilide to obtain high enantioselectivity. The size and structural effects of the ortho substituents on anilide were investigated, and a wide variety of axially chiral anilides that possess various functional groups could be synthesized with high enantioselectivities. This method is the only general way to access a variety of axially chiral anilides in a highly enantioselective fashion reported to date.
authors.affiliation: Laboratory of Synthetic Organic Chemistry and Special Laboratory of Organocatalytic Chemistry, Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502 (Japan), Fax: (+81) 75-753-4041.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.forename: Xiangfei
authors.initials: X
authors.lastname: Wu
authors.forename: S B Jennifer
authors.initials: SB
authors.lastname: Kan
authors.forename: Seiji
authors.initials: S
authors.lastname: Shirakawa
authors.forename: Keiji
authors.initials: K
authors.lastname: Maruoka
keywords: alkylation; anilides; asymmetric synthesis; phase-transfer catalysis; synthetic methods