Benzoic acid, 2-(isocyanatosulfonyl)-, methyl ester → Benzoic acid, 2-(((((6-chloro-3,4-dihydro-4-methyl-3-oxopyrazinyl)amino)carbonyl)amino)sulfonyl)-, methyl ester

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Reaction Steps

To a mixture of 3-amino-5-chloro-1-methyl-2(1H)-pyrazinone (0.40 g, 0.0025 mol) in anhydrous 1,2-dichloroethane (4 mL) under nitrogen was added a solution of 2-carbomethoxybenzenesulfonyl isocyanate (0.84 g, 0.0035 mol) in anhydrous 1,2-dichloromethane (3 mL). The mixture was heated at reflux for 2 hours. The solvent was rotary evaporated, and the residue was purified by chromatography on a column of silica gel using a solvent mixture of 1:1 hexanes-acetone containing a little acetic acid as eluant. Rotary evaporation of the appropriate fractions left 0.34 g of methyl 2-[[(6-chloro-3,4-dihydro-4-methyl-3-oxo-2-pyrazinylamino)carbonylamino]sulfonyl]benzoate as a crystalline powder melting at 173°-176° C.

Provenance & Evidence