C−F Bond Activation by Modified Sulfinatodehalogenation:  Facile Synthesis and Properties of Novel Tetrafluorobenzoporphyrins by Direct Intramolecular Cyclization and Reductive Defluorinative Aromatization of Readily Available β-Perfluoroalkylated Porphyrins

A facile and efficient synthesis of various novel fluorinated extended porphyrins has been developed. The method is based on the direct intramolecular cyclization and reductive defluorinative aromatization of readily available β-perfluoroalkylated porphyrins by highly selective C−F bond activation under modified sulfinatodehalogenation reaction conditions. Various β-(ω-chloroperfluoroalkyl)-meso-tetraphenylporphyrins prepared readily by sulfinatodehalogenation reaction or palladium-catalyzed cross-coupling reaction were treated with Na₂S₂O₄/K₂CO₃ (10:10 equiv per R_F tail) in DMSO at 100 °C for 10−30 min, resulting in good yields of novel β-tetrafluorobenzo-meso-tetraphenylporphyrins. That further reduction of C−F bonds of the products was not observed under the optimal conditions indicates the high selectivity of the reaction. It was found that the amount of sodium dithionite, base, and central metal ion of substrate porphyrins play important roles in the reaction. Detailed mechanism investigations and systematic studies on X-ray crystallographic structure and photophysical and electrochemical properties of a series of new tetrafluorobenzoporphyrins are also reported.