Construction of chiral α- tert -amine scaffolds via amine-catalyzed asymmetric Mannich reactions of alkyl-substituted ketimines

Stereoselective Mannich reactions of aldehydes with ketimines provide chiral β-amino aldehydes that bear an α- -amine moiety. However, the structural variation of the ketimines is limited due to the formation of inseparable / isomers, low reactivity, and other synthetic difficulties. In this study, a highly diastereodivergent synthesis of hitherto difficult-to-access β-amino aldehydes that bear a chiral α- -amine moiety was achieved using the amine-catalyzed Mannich reactions of aldehydes with less-activated -ketimines that bear both alkyl and alkynyl groups.