Titanium(IV) Bromide and Boron(III) Tribromide Promoted Baylis-Hillman Reactions of Arylaldehydes with But-3-yn-2-one

Abstract

The reaction of arylaldehydes with but -3-yn-2-one in the presence of the Lewis acids titanium (IV) bromide (TiBr^4) or boron(III) tribromide (BBr^3) (1,4 equiv.) can be drastically affected by the reaction temperature. When the reaction was carried ort at ≤-20°, the brominated compound 1 was obtained as the major product. However, when the reaction was carried out at room temperature (20°), both the brominated compound 1 and dibrominated compound 2 were formed as major products. The substituent on the phenylring can affect the (E)/(Z) ratio. Moreover, with 2 as jthe substrate, the Pd-catalyzed allylic substitution and Suzuki-type coupling reaction have been examined.