A mild and convenient protocol for the synthesis of quinoxalin-2(1)-ones and benzimidazoles.

We present a mild and simple method for the cyclization of -protected -phenylenediamines with carbonyl compounds in the presence of trifluoroacetic acid. This method reliably provides various substrates of benzimidazoles and quinoxalin-2(1)-ones, with all reactions conducted at room temperature, demonstrating excellent substrate adaptability and a broad substrate scope.