Cooperative Thiourea–Brønsted Acid Organocatalysis: Enantioselective Cyanosilylation of Aldehydes with TMSCN
journal contributionposted on 22.02.2016, 12:32 authored by Zhiguo Zhang, Katharina M. Lippert, Heike Hausmann, Mike Kotke, Peter R. Schreiner
We report a new thiourea–Brønsted acid cooperative catalytic system for the enantioselective cyanosilylation of aldehydes with yields up to 90% and enantioselectivities up to 88%. The addition of an achiral acid was found to be crucial for high asymmetric induction. Mechanistic investigations using a combination of NMR, ESI-MS, and density functional theory computations (including solvent corrections) at the M06/6-31G(d,p) level of theory suggest that the key catalytic species results from the cooperative interaction of bifunctional thioureas and an achiral acid that form well-defined chiral hydrogen-bonding environments.