Sulfuric Acid → N,N'-Dicyclohexylurea

참여 물질

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A solution containing 10.3 g of (V) in the form of sodium salt in 100 ml of water is cooled to 0-5° C. and adjusted to pH 2-3 with a 2 M sodium bisulfate solution. The reaction mixture is stirred at 0° C. for 15 minutes and then CH2Cl2 (70 ml) is added. The two phases are separated and the aqueous layer extracted once with CH2Cl2 (1×50 ml). The combined organic phases are washed with a saturated solution of NaCl (1×25 ml) (360 g/l) and dried over anhydrous Mg2SO4 (3 g, KF 0.12%). After filtration, the solution is concentrated under vacuum at room temperature until 100 mL. To the yellow solution 12 g of (VI) are added, followed by 0.175 g (1.42 mmol) of dimethylaminopyridine (DMAP) and, after complete dissolution of the reagent, 5.88 g of dicyclohexylcarbodiimide (DCC). The reaction mixture is stirred at room temperature for an hour. No starting (VI) is detected by TLC (ethyl acetate/hexane:1/2, detection by spraying with a solution containing H2SO4 (31 mL), ammonium molybdate (19 g) and (NH4)4Ce(SO4)4.2 H2O (1.9 g) in water (500 mL) and heating at 130° C. for 5 min). The precipitate of dicyclohexylurea (DCU) formed is filtered off and washed with CH2Cl2 (1×20 mL). The chloromethylene solution is evaporated to dryness yielding 24 g of (VII).

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