Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction

M Shi; Y S Feng

doi:10.1021/jo0009853

Titanium(IV) chloride and quaternary ammonium salt promoted Baylis-Hillman reaction

J Org Chem. 2001 Jan 26;66(2):406-11. doi: 10.1021/jo0009853.

Authors

M Shi¹, Y S Feng

Affiliation

¹ Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032 China. mshi@pub.sioc.ac.cn

PMID: 11429807
DOI: 10.1021/jo0009853

Abstract

The Baylis-Hillman reaction of aldehydes with alpha,beta-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at -78 degrees C using catalytic amounts of quaternary ammonium salts (R4N+X-, X = Cl, Br, I) as Lewis bases, in the presence of titanium(IV) chloride, the chlorinated aldol adduct 1 was obtained as the major product. Quaternary ammonium bromides and iodides (R4N+X-, X = Br, I) have higher catalytic activity than corresponding chlorides (R4N+Cl-). Quaternary ammonium fluorides (R4N+F-) do not have activity at all. The amounts of Lewis acid and quaternary ammonium salts used affect the reaction rate and product. A plausible reaction mechanism is proposed. If the reaction was carried out at room temperature (about 20 degrees C) in the presence of titanium(IV) chloride and quaternary ammonium salts (R4N+X-, X = Cl, Br, I), the elimination product 3, derived from 1, was formed as the major product.