1. ChemInform Abstract: Titanium(IV) Chloride and Quaternary Ammonium Salt Promoted Baylis-Hillman Reaction
- Author
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Min Shi and Yan-Shu Feng
- Subjects
Reaction mechanism ,Chemistry ,General Medicine ,Medicinal chemistry ,Chloride ,Adduct ,Reaction rate ,chemistry.chemical_compound ,Aldol reaction ,medicine ,Baylis–Hillman reaction ,Ammonium ,Lewis acids and bases ,medicine.drug - Abstract
The Baylis−Hillman reaction of aldehydes with α,β-unsaturated ketones can be drastically affected by the reaction temperature and Lewis bases. When the reaction was carried out at −78 °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 °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.
- Published
- 2010
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