Clonidine → 1-Isonicotinoyl-2-(2',6'-dichlorophenylamino)-2-imidazoline

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Reaction Steps

2.7 g (21.0 millimoles) of isonicotinic acid are added to 800 ml of absolute tetrahydrofuran, 4.2 g (25.9 millimoles) of N,N'-carbonyl-diimidazole are introduced and the mixture is refluxed for 2 hours. When it has cooled, a solution of 5.0 g (21.7 millimoles) of 2-(2',6'-dichlorophenylamino)-2-imidazoline in 100 ml of absolute tetrahydrofuran is added and the batch is stirred for 50 hours at room temperature. It is then freed from solvent on a rotary evaporator, the oily residue is taken up in 500 ml of tetrahydrofuran and the solution is added dropwise, with stirring, to 1.5 liters of 0.1% strength sodium bicarbonate solution. The crystals obtained (6.5 g) are recrystallized once from a 100:140 isopropanol/petroleum ether mixture and once from pure isopropanol. 3.0 g of pure 1-isonicotinoyl-2-(2',6'-dichlorophenylamino)-2-imidazoline are obtained, melting point 82.5°-83.5° C. (the product contains 0.5 mole of isopropanol of crystallization).

Provenance & Evidence