Hydrochloric Acid → 3,4-Dihydro-2-methyl-4-oxo-2H-1,2-benzothiazine-3-carboxylic Acid-1,1-dioxide

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Reaction Steps

To 6.34 g (0.03 mole) 3,4-dihydro-2-methyl-4-oxo-1,2-benzothiazine 1,1-dioxide, 19.5 g (0.15 mole) methylmagnesiumcarbonate in 150 ml N,N-dimethyl formamide were added. The mixture was stirred at 140°-150° C. for 2 hours. The resulting solution was poured quickly into a mixture of 200 ml conc-hydrochloric acid, 200 g ice chips and 500 ml diethyl ether. After stirring the mixture for 10 minutes, the diethylether layer was separated and the separated diethyl ether solution was evaporated in vacuo. The precipitated pale yellow crystals were filtered and recrystallized in dilute methanol solution to obtain 7.21 g of the title compound as white crystals. Yield: 94%

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