Hydrochloric Acid → Benzothiazole

Participants

Reaction Steps

87.9 g of 95% pure 2-mercaptobenzothiazole, 111.7 g of iron filings, 11.8 g of nickel chloride (NiCl2 ×6H2O) and 250 ml of methanol were first introduced into a stirred flask, and the mixture was heated to the reflux temperature with stirring. 165 ml of conc. aqueous hydrochloric acid were added dropwise at 70° C. over a period of 2 hours, and the evolving hydrogen sulphide was trapped in aqueous sodium hydroxide solution. The mixture was additionally stirred at 70° C. for 1 hour and then diluted with 200 ml of water. 200 ml of methanol were distilled off. The remaining mixture was brought to a pH of 5.6 with aqueous sodium hydroxide solution and steam distilled. The steam distillate was extracted with toluene. Removal of the solvent by distillation gave 66.3 g of crude, colourless benzothiazole, 93.7% pure (GC), which corresponds to a yield of 92% of theory, having a residual toluene content of 5.3%.

Provenance & Evidence