Propargyl bromide → HCID 22158393, compound

Participants

Reaction Conditions

Reaction Steps

In 100 ml of n-butanol was dissolved 5.0 g of 2-amino-6-methoxybenzothiazole. With heating at 100° C., 25.0 g of propargyl bromide was dropwise added to the solution over 2 hours. The mixture was heated for a further 2 hours. After completion of the reaction, the solvent was evaporated to dryness. After the residue was crystallized with acetone, the crystals were recrystallized from isopropyl alcohol to give 25.1 g of 2-imino-6-methoxy-3-propargylbenzothiazole hydrobromide. The hydrobromide, 24.0 g, was added to sodium ethoxideethanol solution(Na, 2.0 g) followed by refluxing for 1.5 hours. After the reaction mixture was evaporated to dryness, water and ethyl acetate were added to the residue followed by separation. The residue obtained from the ethyl acetate phase was dissolved in ethanol and reacted with hydrochloric acid to convert the same into the hydrochloride. Recrystallization from 95% ethanol gave 17.3 g of 7-methoxy-2-methylimidazo[2,1-b]benzothiazole hydrochloride. The hydrochloride, 17.0 g, was added to a mixture of 10 ml of phosphorus oxychloride and 180 ml of dry dimethylformamide. After stirring at room temperature for one hour, the mixture was heated at 60° C. for 7 hours. The reaction solution was evaporated to dryness and the residue was dissolved in water. The solution was alkalized with potassium carbonate and extracted with chloroform. From the chloroform phase, 14.2 g of 3-formyl-7-methoxy-2-methylimidazo[2,1-b]benzothiazole was obtained. The obtained formyl compound, 3.7 g, was suspended in methanol and treated with 1.0 g of sodium borohydride. The reaction mixture was evaporated to dryness, and the obtained residue was recrystallized from ethanol to give 3.5 g of the title compound.

Provenance & Evidence