Highly enantioselective cyanation of aldehydes catalyzed by a multicomponent titanium complex.
A new multicomponent bifunctional catalytic system based on a titanium complex was used for the efficient enantioselective cyanation of aldehydes. The catalyst was readily prepared from tetraisopropyl titanate (Ti(Oi-Pr)4), (S)-6,6'-dibromo-1,1'-bi-2-naphthol (1e), cinchonine (2a), and (1R,2S)-(-)-N-methylephedrine (3b). It was revealed that the combination of 1e, 2a, 3b, and Ti(IV) was essential in this cyanation. The reaction proceeded smoothly in the presence of a catalytic amount of the multicomponent catalyst to afford the desired cyanohydrins ethyl carbonates in moderate to excellent isolated yields (up to 95%) with high enantioselectivities (up to 94% ee). A catalytic cycle based on experimental phenomena was proposed to explain the origin of the asymmetric induction.
Gou
Shaohua
S
Key Laboratory of Green Chemistry & Technology, Sichuan University, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, China.
Chen
Xiaohong
X
Xiong
Yan
Y
Feng
Xiaoming
X
D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D003485:Cyanates / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D014025:Titanium / Q000737:chemistry*
D000447:Aldehydes; D003485:Cyanates; D014025:Titanium