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Remarkable Differences in Reactivity between Benzothiazoline and Hantzsch Ester as a Hydrogen Donor in Chiral Phosphoric Acid Catalyzed Asymmetric Reductive Amination of Ketones
Author(s) -
Kim KyungHee,
Akiyama Takahiko,
Cheon CheolHong
Publication year - 2016
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.201501020
Subject(s) - reductive amination , chemistry , moiety , catalysis , aldimine , organic chemistry , phosphoric acid , amination , medicinal chemistry , reactivity (psychology) , medicine , alternative medicine , pathology
Described herein are differences in behavior between a Hantzsch ester and a benzothiazoline as hydrogen donors in the chiral phosphoric acid catalyzed asymmetric reductive amination of ketones with p ‐anisidine. The asymmetric reductive amination of ketones with a Hantzsch ester as a hydrogen donor provided the corresponding chiral amines exclusively, regardless of the structures of the ketones, whereas a similar transformation with a benzothiazoline provided chiral amines and p ‐methoxyphenyl‐protected primary amines in variable yields, depending on the structures of both the ketones and benzothiazolines. Because a benzothiazoline has an N,S‐acetal moiety that is vulnerable to p ‐anisidine, the primary amine can be formed through transimination of the benzothiazoline with p ‐anisidine followed by reduction of the resulting aldimine with remaining benzothiazoline.