Methyl isothiocyanate → N-Methyl-1-(2-methylimidazo[1,2-a]pyridin-6-yl)-2-oxocyclohexanecarbothioamide

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Reaction Steps

In a nitrogen atmosphere, a solution of 35.79 g (0.157 mol) of the 2-(2-methylimidazo[1,2-a]pyridin-6-yl)cyclohexanone prepared in the Preparative Example 2 in 550 ml of tetrahydrofuran was cooled with ice, followed by the addition of 19.55 g (0.174 mol) of potassium t-butoxide. The obtained yellow solution was stirred under cooling with ice for one hour, followed by the addition of a solution of 11.8 ml (0.173 mol) of methyl isothiocyanate in 50 ml of tetrahydrofuran and 50 ml of N,N-dimethylformamide in this order. The obtained reaction mixture was stirred under cooling with ice for one hour, followed by the addition of a saturated aqueous solution of ammonium chloride. The obtained mixture was extracted with chloroform. The organic phase was washed with a saturated aqueous solution of common salt, dried over anhydrous magnesium sulfate, and concentrated in a vacuum. In the course of the concentration, a crystal began to precipitate. This crystal was recovered by filtration. 37.09 g of the title compound was obtained as a colorless crystal. Further, the mother liquor (14.5 g) was purified by silica gel column chromatography [solvent: dichloromethane/methanol (100:3)] and recrystallized from dichloromethane/ethyl acetate to give 3.21 g of the title compound as a pale-pink crystal. Thus. 40.3 g of the title compound was obtained in total (yield: 85%).

Provenance & Evidence