Titanium(IV) chloride and oxy-compounds promoted Baylis–Hillman reaction

Abstract

The Baylis–Hillman reaction of aryl aldehydes with α,β-unsaturated ketones in the presence of titanium(IV) chloride can be promoted by oxy-compounds at room temperature, although they are not as effective as amines, chalcogenides, or quaternary ammonium salts. The oxy-compounds can be simple alcohols, ethers, and ketones. For aryl aldehydes having a strong electron-withdrawing group on the phenyl ring such as nitrobenzaldehyde or p-trifluoromethylbenzaldehyde, the chlorinated compound 1 is obtained as the major product. However, for other aryl aldehydes, the elimination compound 3 was formed predominantly. We also found that TiCl 4·2THF or TiCl 4·2Et 2O complex is very effective for this reaction to give the chlorinated products in high yields at low temperature. A plausible mechanism is proposed.