An "on-water" exploration of CuO nanoparticle catalysed synthesis of 2-aminobenzothiazoles

An "on-water" one-pot process has been engineered for the preparation of 2-aminobenzothiazole from ortho-halo (-F, -Cl, -Br and -I) substituted unsymmetrical thioureas. For ortho -I and -Br substrates the reactions afford 2-aminobenzothiazoles under metal free condition promoted by base. However, the relatively inert ortho -Cl and -F substrates undergo intramolecular arylthiolation only in the presence of CuO nanoparticles yielding 2-aminobenzothiazoles. This methodology provides easy access to aminobenzothiazoles utilising even the ortho -Cl and -F substrates. The catalyst is recyclable several times without loss of substantial activity. Other remarkable features include the wide range of functional group tolerance, absence of chromatographic purification (for ortho -I and -Br substrates) and providing moderate to excellent yield of the products under mild conditions, thus rendering the methodology as a highly eco-friendly alternative to the existing methods.