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Abstract

Reaction of methyl 3-chlorodifluoropropenoate (I) with potassium fluoride afforded methyl trifluoropropenoate (II) which was dimerized to dimethyl perfluro-4-methyl-2-pentenedioate (III). The reaction rate of I was not affected by the presence of the monomer II. Methyl 2-chlorodifluoropropenoate (VII) on treatment with potassium fluoride underwent dimerization and the unstable dimer X was transformed at -20 °C into methyl 2-chloro-3,5,5-trifluoro-4-methoxycarbonyl-2,4-pentadienoate (XIII) and dimethyl 2-chloro-3-fluoro-4-trifluoromethyl-2-pentenedioate (XIV). These reactions involve a transfer of chlorine atom from the dimer X to the primarily formed 1-chloro-3,3,3-trifluoro-1-methoxycarbonylethanide (VIIa) which is transformed by this carbanion interconversion into methyl 2,2-dichlorotrifluoropropanoate (XI). The propenoate VII adds methanol in the presence of potassium fluoride whereas the propenoate I does not react under these conditions.