Enantioselective formal [3+3] cycloadditions of ketones and cyclic 1-azadienes by cascade enamine-enamine catalysis

Abstract

An asymmetric formal [3+3] cycloaddition process with diversely structured aliphatic ketones and electron-deficient cyclic 1-azadienes was developed by cascade enamine-enamine catalysis of a cinchona-based primary amine. This sequence involved a domino Michael addition-Mannich reaction to afford spirocyclic architectures in excellent diastereo- and enantioselectivity. Importantly, high regioselectivity was realized for a number of unsymmetrical aliphatic ketone substrates.

Keywords: [3+3] cycloaddition; aminocatalysis; cascade catalysis; enantioselectivity; regioselectivity.