PREPARATION OF BETA, BETA-DIFLUORO-ALPHA-(TRIFLUOROMETHYL)STYRENES BY PALLADIUM-CATALYZED COUPLING OF ARYL IODIDES WITH PENTAFLUOROPROPEN-2-YLZINC REAGENT

Substituted aromatic iodides are functionalized by pentafluoropropen-2-ylzinc, CF3C(ZnX)=CF2 (X = Br, I, or CF2=CCF3-), in the presence of Pd(PPh3)4 to give the corresponding arenes in good yields. This is particularly attractive for preparation of title styrenes substituted with groups such as -NO2 or CO2R, which are incompatible with organomagnesium reagents. The best yields of the title styrenes with electron-donating substituents were obtained in DMF. For electron-withdrawing substituents, the best results were achieved in triglyme. A correlation was observed between Hammett sigma constants and F-19 NMR chemical shifts (R = 0.93-0.99, n = 8) and 2J(F-F) coupling constants (R = 0.94, n = 8).