Pinpoint-Fluorinated Phenacenes: New Synthesis and Solubility Enhancement Strategies

The Pd(II)-catalyzed cyclizations of 2,2-difluorovinylated biaryls, following a Friedel-Crafts-type mechanism, provide a new route to pinpoint-fluorinated phenacenes. The single fluorine substituent stabilized the synthesized fluoropicenes (fluoro[5]phenacenes) toward aerial oxidation and contributed to their solubility in organic solvents. For example, 6- and 13-fluoropicenes were 25- and 15-fold more soluble in THF than nonfluorinated picene. X-ray crystal structure analysis revealed that the fluorine substituent did not alter molecular planarity.