Cooperative thiourea-Brønsted acid organocatalysis: enantioselective cyanosilylation of aldehydes with TMSCN.
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.
Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
Zhiguo
Z
Zhang
Katharina M
KM
Lippert
Heike
H
Hausmann
Mike
M
Kotke
Peter R
PR
Schreiner
D000143:Acids / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D003486:Cyanides / Q000737:chemistry*; D015394:Molecular Structure; D009570:Nitriles / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013890:Thiourea / Q000737:chemistry*; D014297:Trimethylsilyl Compounds / Q000737:chemistry*
D000143:Acids; D000447:Aldehydes; D003486:Cyanides; D009570:Nitriles; D014297:Trimethylsilyl Compounds; C058010:trimethylsilyl cyanide; D013890:Thiourea