T. Takagi et al., A METHOD FOR SYNTHESIS OF FLUORINE-COMPOUNDS USING ABNORMAL GRIGNARD REACTION OF HALOTHANE .2. REACTION WITH ALDEHYDES AND UNSATURATED-KETONES, Chemical and Pharmaceutical Bulletin, 43(7), 1995, pp. 1071-1075
In an abnormal Grignard reaction of halothane, the primary Grignard re
agent reacts with another mole of halothane to give 1-bromo-1-chloro-2
,2,2-trifluoroethylmagnesium bromide, which in turn reacts with a carb
onyl compound to give 1-bromo-1-chloro-2,2,2-trifluoroethyl carbinols
and their dehalogenation products, 1-chloro-2,2-difluoroethenyl carbin
ols. We examined the application of this method to aldehydes and to un
saturated ketones. Aldehydes were much less reactive than ketones, and
needed higher reaction temperature. However, elevation of temperature
caused dehalogenation of the primary products to 1-chloro-2,2-difluor
oethenyl derivatives. These derivatives were treated with hydrogen flu
oride to afford 1-chloro-1-(trifluoromethyl)ethene derivatives. The re
action of cc,P-unsaturated ketones mainly gave 1,2-addition products o
f the Grignard reagent, while 3-methyl-2-cyclohexenone gave mainly the
1,4-adducts.