Cu(II)-Catalyzed Cascade of N -Phenyl- o -phenylenediamine with Benzaldehyde: One-Step Direct Construction of 2-(1-Phenyl-1 H -benzo[ d ]imidazol-2-yl)phenols.

A practical protocol for the construction of hydroxylated 2-(1-phenyl-1 H -benzo[ d ]imidazol-2-yl)phenols (PBIs) from N -phenyl- o -phenylenediamine with benzaldehydes was developed. The cascade reaction was enabled by heating a mixture of the two substrates in the presence of air as an oxidant and anhydrous Cu(OAc) 2 as a catalyst in dimethyl sulfoxide, and a diverse series of PBIs were synthesized in moderate to good yields (69-81%). Furthermore, the synthesis of the PBIs was enabled via a one-pot cascade reaction that proceeded through subsequent dehydration condensation, intramolecular cyclization, and aromatic C-H hydroxylation. This protocol can be used for the synthesis of hydroxylated PBI via a one-pot annulation C-H hydroxylation reaction rather than through a series of multistep reactions, which provides the possibility of further modification.