A green method for the synthesis of 2-arylbenzothiazoles

Aromatic aldehydes with both electron withdrawing and electron donating substituents were smoothly converted to the corresponding 2-arylbenzothiazoles by direct condensation of aromatic aldehydes with 2-aminothiophenol in one pot in a microoven under solvent-free conditions without any catalyst. The study revealed that the synthesis proceeded in three stages; first the formation of the aryl imine followed by its cyclisation to the benzothiazoline which in turn underwent oxidation and dehydration to the final product benzothiazole. Isolation of intermediates in all the stages confirmed the mechanism. This is therefore the first report of a green synthesis of the 2-arylbenzothiazoles under solvent-free conditions in the absence of any catalyst.