Urea → p-(tetrahydro-4H-1,4-thiazin-4-yl)phenol

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Reaction Steps

2.34 g of 4-(p-aminophenyl)-tetrahydro-4H-1,4-thiazine are dissolved in 12 ml of 35 percent sulfuric acid, 12 g of ice are added thereto, a cold solution of 1.05 g of sodium nitrite in 12 ml of water is then slowly introduced under the surface and the mixture is stirred for 5 minutes at about 0°. Thereafter, there are added 60 mg of urea, a solution of 144 g of copper(II) nitrate trihydrate in 420 ml of water and finally while stirring vigorously 1.59 g of copper(I) oxide. The mixture is stirred for 5 minutes, adjusted to about pH 6 with sodium hydroxide solution and extracted three times with 600 ml of dichloromethane each time and once with 600 ml of dichloromethane/ethanol (4:1). The organic phases are washed twice with 300 ml of water each time, dried over sodium sulfate and evaporated. The crude product is chromatographed on 400 g of silica gel with dichloromethane which contains 5% acetone. The material obtained is recrystallized from dichloromethane/methanol/ether, whereby there is obtained p-(tetrahydro-4H-1,4-thiazin-4-yl)phenol of melting point 155°-157°.

Provenance & Evidence