A Method for Synthesis of Fluorine Compounds Using Abnormal Grignard Reaction of Halothane. II. Reaction with Aldehydes and Unsaturated Ketones

摘要

In an abnormal Grignard reaction of halothane, the primary Grignard reagent reacts with another mole of halothane to give l-bromo-l-chloro-2,2,2-trifluoroethylmagnesium bromide, which in turn reacts with a carbonyl compound to give l-bromo-l-chloro-2,2,2-trifluoroethyl carbinols and their dehalogenation products, l-chloro-2,2-difluoroethenyl carbinols. We examined the application of this method to aldehydes and to unsaturated ketones. Aldehydes were much less reactive than ketones, and needed higher reaction temperature. However, elevation of temperature caused dehalogenation of the primary products to l-chloro-2,2-difluoroethenyl derivatives. These derivatives were treated with hydrogen fluoride to afford l-chloro-l-(trifluoromethyl)ethene derivatives. The reaction of oc,/i-unsaturated ketones mainly gave 1,2-addition products of the Grignard reagent, while 3-methyl-2-cyclohexenone gave mainly the 1,4-adducts.