2-Chloro-6-methylaniline → Tert-butyl (5-((2-chloro-6-methylphenyl)carbamoyl)thiazol-2-YL)carbamate

The fourth step involves adding 2-chloro-6-methylaniline to a stirred solution of tert-butyl[5-(chlorocarbonyl)-1,3-thiazol-2-yl]carbamate in dichloromethane at 0° C. Diisopropylamine was added to the reaction mixture, warmed to room temperature, stirred for 24 hours, diluted with dichloromethane, and washed with 2N hydrochloric acid. The organic extract thus obtained was dried, filtered, and concentrated to obtain a residue. The residue was diluted with ethyl acetate-ether, filtered, washed with ether, and dried in vacuo to obtain tert-butyl{5-[(2-chloro-6-methylphenyl)carbamoyl]-1,3-thiazol-2-yl}carbamate (Formula 1b) in an overall yield of 48%.