Hydrochloric Acid → 2-Methyl-3-Nitroso-8-(Phenylmethoxy)imidazo[1,2-a]pyridine

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Reaction Steps

To a stirred mixture of 10.0 g (42.2 mmol) of 2-methyl-8-(phenylmethoxy)imidazo[1,2-a]pyridine, 150 ml of water and 150 ml of chloroform is added cautiously (EXOTHERM) 179.5 ml (2.15 moles) of concentrated hydrochloric acid and the resultant mixture is heated to an internal temperature of approximately 55° C. To this stirred and heated mixture is added at a rate of approximately 7 ml/minute a solution of of 151 g (2.11 moles) sodium nitrite (97%) in 660 ml of water to produce a vigorous, but manageable, reflux. When the addition is complete,the reaction mixture is allowed to cool to room temperature. The lower (CHCl3) layer is drawn off and the aqueous layer extracted with three--150 ml portions of chloroform. The combined chloroform extracts arewashed with two--450 ml volumes of 2.4 M sodium carbonate solution, then with a single 500 ml portion of saturated aqueous sodium chloride. The extracts are concentrated in vacuo (rotary evaporator, 45°) to lessthan one-half the original volume, dried over anhydrous sodium sulfate and evaporated to a viscous oil. Chromatography of the oil on silica gel, eluting with chloroform/ethyl acetate (1/1) yields the title compound as acrystalline solid, mp 147.5°-149.5° C. (dec).

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