Dual activation in oxidative coupling of 2-naphthols catalyzed by chiral dinuclear vanadium complexes

• Published in: Tetrahedron 2008-04, Vol.64 (15), p.3361-3371
• Main Authors: Takizawa, Shinobu, Katayama, Tomomi, Somei, Hidenori, Asano, Yasuaki, Yoshida, Tomokazu, Kameyama, Chiaki, Rajesh, Doss, Onitsuka, Kiyotaka, Suzuki, Takeyuki, Mikami, Masafumi, Yamataka, Hiroshi, Jayaprakash, Doss, Sasai, Hiroaki
• Format: Article
• Language: English
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2008.01.110

An efficient enantioselective oxidative coupling of 2-naphthol derivatives based on a concept of dual activation catalysis is realized. A chiral dinuclear vanadium(IV) complex ( R a, S, S)- 1e possessing ( S)- tert-leucine moieties at the 3,3′-positions of the ( R)-binaphthyl skeleton was developed, which was found to promote the oxidative coupling of 2-naphthol to afford ( S)-BINOL with 91% ee. To verify the dual activation mechanism, mononuclear vanadium(IV) complex ( S)- 8 was also prepared. Kinetic analysis revealed that the reaction rate of oxidative coupling of 2-naphthol promoted by ( R a, S, S)- 1e is 48.3 times faster than that of ( S)- 8. The two vanadium metals in the chiral complex activate two molecules of 2-naphthol simultaneously in an intramolecular manner coupling reaction, achieving a high reaction rate with high enantiocontrol. Reaction mechanisms of the oxidative coupling reaction promoted by either vanadium(IV) or vanadium(V) complexes are also described. [Display omitted]