1. Efficient bimetallic titanium catalyst for carbonyl-ene reaction
- Author
-
Fang, Fang, Xie, Fang, Yu, Han, Zhang, Hui, Yang, Bo, and Zhang, Wanbin
- Subjects
- *
METAL catalysts , *TITANIUM , *CARBONYL compounds , *BIPHENYL compounds , *LIGANDS (Chemistry) , *CHIRALITY , *STYRENE - Abstract
Abstract: A new family of achiral 3,3′,5,5′-tetrasubstituted-2,2′,6,6′-tetrahydroxy biphenyl ligand 4 was developed. The axial chirality of the ligand could be induced by the chelation of 2,2′,6,6′-tetrahydroxy groups with (R)-BINOL-Ti(O i Pr)2 to form an axially chiral bimetallic titanium catalyst 9. Compared with (R)-BINOL-Ti(O i Pr)2 catalyst, this novel catalyst 9 exhibited excellent activity and enantioselectivity for the carbonyl-ene reaction of methylstyrene and ethyl glyoxylate. 3,3′,5,5′-Tetrasubstituted groups showed a remarkable effect on both enantioselectivity and yield. With 9d prepared from 3,3′,5,5′-tetramethyl-2,2′,6,6′-tetrahydroxy biphenyl 4d as the catalyst, the best result, up to 97.6% ee and 99% yield, was obtained. Additionally, the bimetallic catalyst 9 also showed better catalytic capability than the corresponding monometallic catalyst. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF