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

A practical protocol for the construction of hydroxylated2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenols(PBIs)from N-phenyl-o-phenylenediaminewith benzaldehydes was developed. The cascade reaction was enabledby heating a mixture of the two substrates in the presence of airas an oxidant and anhydrous Cu(OAc)(2) as a catalyst in dimethylsulfoxide, and a diverse series of PBIs were synthesized in moderateto good yields (69-81%). Furthermore, the synthesis of thePBIs was enabled via a one-pot cascade reaction that proceeded throughsubsequent dehydration condensation, intramolecular cyclization, andaromatic C-H hydroxylation. This protocol can be used for thesynthesis of hydroxylated PBI via a one-pot annulation C-Hhydroxylation reaction rather than through a series of multistep reactions,which provides the possibility of further modification.

Automated summary

A practical protocol for the synthesis of hydroxylated 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenols (PBIs) through a one-pot cascade reaction has been developed. The cascade reaction involves dehydration condensation, intramolecular cyclization, and aromatic C-H hydroxylation, and is enabled by heating a mixture of N-phenyl-o-phenylenediamine and benzaldehydes in the presence of air and Cu(OAc)2 catalyst in dimethylsulfoxide. The PBIs are obtained in moderate to good yields (69-81%), providing the possibility for further modification.