One-Pot Synthesis of 2-Aryl- and 2-Alkylbenzothiazoles under Microwave Irradiation

Eco-friendly direct solvent-free reactions of o-aminothiophenol and aromatic or aliphatic β-keto esters with microwave irradiation produced 2-substituted benzothiazoles in excellent yield.Experiments that compared microwave irradiation to conventional heating methods showed that the former gives the 2-substituted benzothiazoles faster and in higher yields.The formation of the titled compounds probably involves the nucleophilic addition of the thiol group to the keto group of the β-keto ester with subsequent elimination of ethyl acetate from the resulting adduct.The adduct then undergoes an intramolecular addition of the o-amino group to the carbonyl group to give an adduct from which water is eliminated to afford the 2-substituted benzothiazoles.