The reaction of trifluoroacetaldehyde ethyl hemiacetal or hydrate with an equimolar amount of imine in hexane at reflux temperature for 1 h gave the corresponding β-hydroxy-β-trifluoromethyl ketones in good to excellent yields.
Difluoroacetaldehyde ethyl hemiacetal (1), prepared from ethyl difluoroacetate and lithium aluminum hydride in diethyl ether, was found to be a potential difluoroethylating reagent for the preparation of a wide variety of difluoromethylated compounds. Compound 1 shows promise for use in the synthesis of carbinols prepared by the reaction of 1 with metal reagents or enol silyl ethers, the synthesis of amino acid ketones and beta-lactams via the nucleophilic reaction of imines, and the synthesis of sugar analogues.
The Use of Trifluoroacetaldehyde Ethyl Hemiacetal or Hydrate in a Simple and Practical Regioselective Synthesis of β-Hydroxy-β-trifluoromethyl Ketones from Enamines and Imines
The reaction of trifluoroacetaldehyde ethyl hemiacetal or hydrate with an equimolar amount of enamines, derived from various methylketones, smoothly proceeded to give the corresponding beta-hydroxy-beta-trifluoromethyl ketones in high yields. An equimolar amount of imines derived from various methylketones with aliphatic, aromatic, and heteroaromatic substituents also readily reacted with trifluoroacetaldehyde