General procedure for the synthesis of 2-mercapto-5-methoxybenzothiazole from 4-chloro-3-nitroanisole: 244 g of sodium polysulfide solution was mixed with 30 g of 1-chloro-4-methoxy-2-nitrobenzene, followed by the addition of 20 mL of carbon disulfide and continuous stirring. The reaction mixture was heated to reflux and maintained for about 5 hours, during which time a yellow solid precipitate was observed to form. Upon completion of the reaction, the mixture was filtered and the filtrate was diluted to 1000 mL with water to obtain an orange-yellow solution. The solution was neutralized to neutral with 6 M hydrochloric acid, at which point a light yellow solid precipitated. The solid product was collected by filtration, washed well with water and dried. Finally, 29.4 g of the target product 2-mercapto-5-methoxybenzothiazole was obtained in 93.1% yield.
