Selective Pd-catalyzed α- and β-arylations of the furan rings of (ortho-bromophenyl)furan-2-yl-methanones: C(CO)–C bond cleavage with a furan ring as a leaving group and synthesis of furan-derived fluorenones

Abstract

Selective palladium diacetate-catalyzed α- and β-arylations of the furan rings of (ortho-bromophenyl)furan-2-yl-methanones 1 under two different conditions are reported. In the presence of potassium tert-butoxide as a strong base and triphenylphosphine as a ligand, methanones 1 undergo α-arylation accompanied by C(CO)–C bond cleavage. In contrast, in the presence of potassium carbonate as the base and tricyclohexylphosphonium tetrafluoroborate as the ligand, methanones 1 undergo intramolecular β-arylation to afford furan-derived fluorenones in high yields from a wide variety of substrates. In addition, a one-pot protocol for the successive direct intramolecular β-arylation and intermolecular α-arylation of the furan rings of 1 has been achieved.