Silylative Reductive Amination of alpha,beta-Unsaturated Aldehydes: AConvenient Synthetic Route to beta-Silylated Secondary Amines

Described here is a reductive amination/hydrosilylation cascade of alpha,beta-unsaturated aldehydes mediated by a Lewis acidic borane catalyst. The present reaction system provides an one-pot synthetic route towards beta-silylated secondary amines that have not been accessible by other previous catalysis. Comparative (HNMR)-H-1 studies on the silylative reduction of enimines revealed that steric bulkiness of primary amine reactants strongly affects both catalytic efficiency and regioselectivity. This strategy was applicable to a broad range of substrates and amenable to one-pot gram-scale synthesis. Moreover, a diastereoselective introduction of the beta-silyl group was also found to be feasible (d.r. up to 71:29) ⓒ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei