BF3-catalyzed room-temperature reaction of xenon difluoride with pentafluoro-subtitutd benzene derivatives resulted in 1, 4-and 1, a-fluorine addition with regiospecificity depending on the substituent. Reaction with 1-substituted (H, C1, Br, Cas) pentafluorobenzene resulted in the formation of 1-substituted heptafluorocyclohexa-l, 4- dienes, and reactions with n-alkoxy-substituted pentafluorobenzenes resulted in two types ...