Bis(μ-oxo)–Dititanium(IV)–Chiral Binaphthyldisulfonate Complexes for Highly Enantioselective Intramolecular Hydroalkoxylation of Nonactivated Alkenes

Abstract

A series of chiral 1,1′-binaphthyl-2,2′-disulfonic acids was designed, synthesized, and applied in a highly enantioselective Ti-catalyzed intramolecular hydroalkoxylation of nonactivated alkenes. The catalyst is probably a complex between two chiral binaphthyldisulfonate ligands and a bis(μ-oxo)–dititanium(IV) core structure. The sulfonamide groups of the ligands and water are necessary for the catalysis, as they may stabilize the catalytically active complex through hydrogen bonding. Various 2-methylcoumarans were obtained in up to greater than 99% yields and up to 97% enantiomeric excess under mild conditions.

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