Methyl iodide → 5-Methyl-4,5,6,7-tetrahydrothiazolo(5,4-c)pyridine

Thiazolo[5,4-c]pyridine (1.61 g) was dissolved in N,N-dimethylformamide (50 ml), and to the solution methyl iodide (1.50 ml) was added, the resultant mixture was stirred at 80° C. for 4 hours. The reaction mixture was concentrated under reduced pressure, and the residue was dissolved in methanol (100 ml), sodium borohydride (1.53 g) was added, and the resultant mixture was stirred at room temperature for 1 hour. The reaction mixture was concentrated under reduced pressure, and a saturated aqueous solution of potassium carbonate and ether were added to the residue to separate an organic layer. The organic layer was dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by column chromatography on silica gel (dichloromethane:methanol 25:1) to obtain the title compound (1.28 g) as a pale yellow oil.