A METHOD FOR SYNTHESIS OF FLUORINE-COMPOUNDS USING ABNORMAL GRIGNARD REACTION OF HALOTHANE .3. SIMPLE SYNTHESIS OF TRIFLUOROMETHYLCHLOROOLEFINS

We have reported an abnormal Grignard reaction of halothane (1) with c arbonyl compounds (2). The reaction afforded 1-bromo-1-chloro-2,2,2-tr ifluoroethylcarbinols (3) as the major products at -53 degrees C, whil e at 0 degrees C, the main products were the dehalogenation products, 1-chloro-2,2-difluoroethenyl carbinols (4). Treatment of 4 with hydrog en fluoride (HF) afforded 1-chloro-1-(trifluoromethyl)ethene derivativ es (5) in good yields. However, this reaction required HF, a dangerous reagent. Here, we describe a much easier and safer synthesis of 5. Th us, treatment of 3 with zinc chloride and acetic anhydride gave acetox y compounds (6). The acetates were converted to the olefins (5) by red uctive debromoacetoxylation with zinc in the presence of a catalytic a mount of copper(I) iodide. Application of this reaction to an alpha,be ta-unsaturated ketone, benzalacetone, gave the diene bearing a trifluo romethyl group.