CONSTRUCTION OF PINPOINT-FLUORINATED BENZOTHIOPHENE FRAMEWORKS USING PALLADIUM-CATALYZED CYCLIZATION OF o-(FLUOROVINYL)PHENYL-SUBSTITUTED THIOPHENES

摘要

o-(2,2-Difluorovinyl)phenyl-or o-(1,2,2-trifluorovinyl)phenyl-substituted thiophenes underwent palladium(II)-catalyzed Friedel-Crafts-type cyclization on the fluorovinyl moieties to construct regioselectively monofluorinated or difluorinated benzothiophene frameworks (pinpoint-fluorinated naphtho[b]thiophenes). The cyclization of less nucleophilic 2-substituted thiophenes was effectively promoted by the addition of a CuOTf complex. Cyclization was also conducted in a tandem process, which facilitated the rapid synthesis of higher-order pinpoint-fluorinated PAHs (polycyclic aromatic hydrocarbons) bearing thiophene rings. Furthermore, cyclization was applied to the corresponding furan systems, which led to pinpoint-fluorinated naphtho[b]furans.