title: A highly enantioselective hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene catalyzed by chiral titanium(IV) 5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol complexes.
abstract: The catalytic effect of chiral Lewis acids on the hetero-Diels-Alder reaction between aldehydes and Danishefsky's diene (1) has been investigated. A variety of combinations of different ligands and Lewis acids have been examined as catalysts for the hetero-Diels-Alder reaction between benzaldehyde and 1, and it has been found that the readily accessible Ti(IV)-H(8)-BINOL (TiHBOL) complex is a very effective catalyst for the reaction, leading to products with very high enantioselectivity (up to 99% ee) and yield (92%). The hetero-Diels-Alder reaction of other aldehydes with 1 under the catalysis of TiHBOL is a general reaction which proceeds well with very high enantioselectivity and isolated yield for various aldehydes at 0 degrees C to room temperature. Based on the experimental results, the proposed mechanism of the hetero-Diels-Alder reaction and the dihedral angle effects of ligands are discussed.
authors.affiliation: The Faculty of Chemistry, Sichuan University, Chengdu 610064, People's Republic of China.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Feng
authors.forename: Yaozong
authors.initials: Y
authors.lastname: Huang
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Xin
authors.initials: X
authors.lastname: Cui
authors.forename: Yaozhong
authors.initials: Y
authors.lastname: Jiang