2-Aminopyridine → 2-Chloromethyl-imidazo(1,2-A)pyridine

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Reaction Steps

A mixture of 4.7 g (0.05 mole) of 2-aminopyridine and 6.4 g (0.05 mole) of 1,3-dichloropropan-2-one in 50 ml of ethanol was stirred overnight at room temperature. The mixture was concentrated in vacuo and the residue was triturated with acetonitrile. The solid that formed was recrystallized from acetonitrile-methanol to yield ca. 1 g of 2-chloromethylimidazo[1,2-a]pyridine as the hydrated hydrochloride salt. [Calcd. for C8H7N2Cl.HCl.H2O: C, 43.42; H, 4.52; N, 12.67; Cl, 32.12. Found: C, 42.94; H, 4.62; N, 12.68; Cl, 32.12.] A mixture of 790 mg (3.89 mmole) of the chloromethyl compound and 585 mg (3.90 mmole) of 2-mercaptobenzimidazole in 200 ml of isopropyl alcohol was stirred for two days. The mixture was concentrated in vacuo and the residue was dissolved in boiling isopropyl alcohol. The precipitate that formed upon cooling was collected and partitioned between saturated aqueous sodium bicarbonate and chloroform. The organic layer was dried over magnesium sulfate, filtered and concentrated in vacuo to a solid. Recrystallization from isopropyl alcohol yielded (in two crops) 500 mg of the title compound as an analytically pure solid, m.p. 220°-222°. Structure assignment was supported by the nmr and infrared spectra and by elemental analysis.

Provenance & Evidence