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Phase‐Transfer‐Catalyzed Asymmetric Synthesis of Axially Chiral Anilides
Author(s) -
Liu Kun,
Wu Xiangfei,
Kan S. B. Jennifer,
Shirakawa Seiji,
Maruoka Keiji
Publication year - 2013
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201301036
Subject(s) - chirality (physics) , enantioselective synthesis , axial chirality , ammonium bromide , axial symmetry , catalysis , bromide , chemistry , steric effects , stereochemistry , combinatorial chemistry , organic chemistry , physics , geometry , chiral perturbation theory , mathematics , pulmonary surfactant , biochemistry , nambu–jona lasinio model , pion , particle physics
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.