Convenient synthesis of methyl 4-carboethoxy-3-perfluoroalkyl-5-methoxyhexa-2,4-dienoates

In the presence of K2CO3, reaction of ethyl 3-methoxy-4-(triphenyl phosphoranylidene)but-2-enoate (2), which was derived from the bromide 1, with methyl 3-perfluoroalkyl-2-propiolates (3) in CH2Cl2 at room temperature, gave methyl 4-carboethoxy-3-perfluoroalkyl-5-methoxy-6-(triphenylphosphoranylidene)hexa-2,4-dienoate (4) as major products in excellent yields. Methyl 4-carboethoxy-3-perfluoroalkyl-5-methoxyhexa-2,4-dienoates (5) were obtained in high yield by hydrolysis of (4) in hot aqueous methanol in a sealed tube. The structure identities of compounds 4 and 5 were confirmed by IR, MS, 1H, 13C NMR, 2D C–H COSY and microanalyses. Reaction mechanisms are proposed to account for the formation of products 4 and 5.