title: Chiral Brønsted acid-catalyzed direct Mannich reactions via electrophilic activation.
abstract: It was found that the phosphoric acid derivatives of general structure 1 serve as highly effective catalysts for the direct addition of acetyl acetone to N-Boc-protected arylimines. The beneficial effects of the 3,3'-bisaryl substituents of the catalysts on the enantioselectivity are greatly appreciated, and thus 1d functions as an excellent catalyst. The Brønsted acid-catalyzed direct Mannich reactions presented herein provide an attractive way to construct beta-aminoketones under extremely mild conditions. The stereochemical course of this reaction was established through the synthesis of Boc-(S)-phenylglycine methylester. The transformation thus demonstrated is applicable to a useful method for the synthesis of various phenylglycine derivatives.
authors.affiliation: Graduate School of Science, Department of Chemistry, Tohoku University, Sendai 980-8578, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Uraguchi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Terada