Synthesis of 2-Substituted 1,3-Benzoselenazoles from Carboxylic Acids Promoted by Tributylphosphine

We report a general, practical, and simple metal-free method for the synthesis of 2-substituted 1,3-benzoselenazoles by the reaction of bis(2-aminophenyl)diselenide with a wide range of carboxylic acids, promoted by tributylphosphine. This efficient reaction furnishes 2-aryl-1,3-benzoselenazoles in good yields and tolerates a variety of substituents at the aryl moiety of carboxylic acids. For the first time, 2-alkyl-1,3-benzoselenazoles could be obtained from aliphatic carboxylic acids and thiazolidine-4-carboxylic acid in high chemical yields. The use of focused microwave irradiation considerably decreased the reaction time from 48 to 2 h. The experimental data provide insights into the mechanism of the reaction.