On water'' organic synthesis: a highly efficient and clean synthesis of 2-aryl/heteroaryl/styryl benzothiazoles and 2-alkyl/aryl alkyl benzothiazolines

A convenient and clean on water -mediated synthesis of benzothiazoles/benzothiazolines is reported. Aromatic, heteroaromatic, and styryl aldehydes are converted to 2-substituted benzothiazoles in high yields in a one- pot reaction with 2-aminothiophenol in water at 110 degrees C ( oil- bath). Alkyl and aryl alkyl aldehydes afforded the benzothiazolines. The reaction is highly chemoselective with no competitive thia- Michael addition, O-dealkylation/ debenzoylation, reduction of the nitro or the alpha, beta-unsaturated carbonyl groups, and substitution of the halogen atom or the nitro group. The reaction is found to be general with respect to the 2-aminothiophenol substrate through the reaction of a few substituted 2-aminothiophenols with a few representative aromatic and aliphatic aldehydes. The procedure does not involve the use of any additional reagent/ catalyst, produces no waste, and represents a green synthetic protocol.