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

The Baylis-Hillman reaction of aryl aldehydes with alpha,beta -unsaturated ketones in the presence of titanium(IV) chloride can be promoted by oxy-com pounds at room temperature, although they are not as effective as amines, c halcogenides, 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-triflu oromethylbenzaldehyde, 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(2) O complex is very effective for this reaction to give the chlorinated produ cts in high yields at low temperature. A plausible mechanism is proposed. ( C) 2001 Elsevier Science Ltd. All rights reserved.