Preparation of trifluoromethylated allylic and homoallylic alcohols from trifluoroacetaldehyde and organometallic compounds

Abstract

Ethyl 4, 4, 4-trifluoro-2-substituted-3-hydroxybutyrate have been synthesized by the Reformatsky-type reaction between trifluoroacetaldehyde and $\alpha$-substituted bromoacetate in tetrahydrofuran with ultrasonic irradiation. The dehydration of hydroxy esters to ethyl 4, 4, 4-trifluorocrotonate have been carried out with phosphorus pentoxide. $\alpha$-Trifluoromethylated allylic alcohols were prepared from the reduction of ester to alcohols with lithium aluminum hydride and aluminum chloride. $\alpha$-Trifluoromethylated allylic alcohols have been derived by the Grignard reaction between vinyl bromide and trifluoroacetaldehyde under ultrasonic irradiation at the mild condition. The reactions of allylmetallic compounds derived from zinc, cadmiun, manganese, chromium (II) with perfluoroaldehyde under ultrasonic irradiation resulted in the formation of homoallylic alcohols with high degree of stereoselectivity. The stereoselective synthesis of $\alpha$-trifluoromethyl allylic alcohols utilizing the hydromagnesation of 1, 1, 1-trifluoro-4-substituted-3-butyn-2-ol have been sucessfully carried out. We also have examined the phenylation of 1, 1, 1-trifluoro-3-buten-2-ol and 1, 1, 1-trifluoro-4-penten-2-ol catalyzed by palladium acetate.