A one-pot strategy for the synthesis of 2-aminobenzothiazole in water by copper catalysis

A straightforward, efficient and sustainable method for the synthesis of 2-aminobenzothiazoles has been achieved from in situ generated 2-halothioureas using copper(I) catalyst in water. The present study demonstrates that copper iodide (CuI) exhibits better efficiency in water towards intramolecular S-arylation compared to organic solvents. While (o-iodoaryl) thioureas are smoothly converted to the desired product in high yields with only catalytic quantity of CuI, addition of base and ligand are essential for bromo and chloro analogues. An unprecedented demethoxylation of o-methoxy-o-iodoarylthiourea and demethoxylation followed by a Friedel-Crafts type methylation (para to nitrogen) was observed in the aryl ring possessing the original methoxy group.