Pyridine → 3,6-Dichloro-4h-thieno[3,2-e][1,2,4]thiadiazine 1,1-dioxide

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Reaction Steps

A suspension of 6-chloro-2,3-dihydro-3-oxo-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (10.75 g, 0.045 mol) in phosphorus oxychloride (100 ml) was cooled on an ice bath and dry pyridine (7.3 ml, 0.09 mol) was added dropwise at such a rate that the temperature did not exceed 10° C. The mixture was then heated at 95°-100° C. for 16 h, and cooled to room temperature. A yellow precipitate was removed by filtration, and the filtrate was concentrated in vacuo. To the residue was added 200 g of ice, and the resulting mixture was stirred for 1 h, and filtered. The isolated solid was dissolved in saturated aqueous sodium hydrogen carbonate (100 ml), and filtered to remove a small amount of insoluble material. After treatment with decolorising charcoal the filtrate was adjusted to pH 2 with 4M hydrochloric acid and the precipitate that formed was filtered, washed with water and dried to yield 5.55 g (48%) of the title compound; mp >240° C. decomp.

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