Hashimoto T, Nakatsu H, Takiguchi Y, Maruoka K * Kyoto University, Japan
Axially Chiral Dicarboxylic Acid Catalyzed Activation of Quinone Imine Ketals: Enantioselective
Arylation of Enecarbamates.
J. Am. Chem. Soc. 2013;
135: 16010-16013
Key words
enecarbamates - dicarboxylic acids - quinone imine ketals
Significance
The asymmetric enantioselective arylation of enecarbamates catalyzed by a chiral Brønsted
acid is reported. An axially chiral dicarboxylic acid (1) catalyzes the reaction of quinone imine ketals 2 with enecarbamates 3 to give α-amino-β-aryl ethers 4 in good yields and enantioselectivities. The products could be transformed into
various useful chiral building blocks.
Comment
It is notable that opposite enantiomers of the products are obtained by changing from
Z- to E-enecarbamates. The authors propose that the isomeric enecarbamates approach the quinone
imine ketals 2 from the same prochiral face, and that diastereomeric intermediates are generated
that lead to the opposite enantiomers after aromatization.
