Titanium(IV) chloride, zirconium(IV) chloride or boron trichloride and phosphine-promoted Baylis–Hillman reaction of aldehydes with α,β-unsaturated ketone

Abstract

In the Baylis–Hillman reaction of aldehydes with an α,β-unsaturated ketone, the chlorinated compound 1 was obtained as the major product using tributylphosphine as a Lewis base in the presence of titanium(IV) chloride, zirconium(IV) chloride or boron trichloride in dichloromethane at <−20 °C. A plausible reaction mechanism has been proposed. Using (R)-(+)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) as a chiral Lewis base, 10% ee could be achieved. We also found that, if the reaction was carried out at room temperature, the dehydrated compound 3 was obtained as the major product in the Z-configuration.