Selenium Dioxide → Methyl 5-[3-,6-dihydro-3-methyl-2,6-dioxo-4-(trifluoromethyl)-1(2H)-pyrimidinyl]-1,2-benzisothiazole-3-glyoxylate

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Reaction Steps

A mixture of ethyl 5-[3,6-dihydro-3-methyl-2,6-dioxo-4-(trifluoromethyl)-1(2H)-pyrimidinyl]-1,2-benzisothiazole-3-acetate(30.0 g, 0.0750 mol), selenium dioxide (15.0 g, 0.135 mol) and glacial acetic acid is stirred two hours at reflux, cooled and filtered through a pad of Celite. The filtrate is concentrated in vacuo and the residue is stirred in methylene chloride. The mixture is filtered and the filtrate filtered through a pad of Celite. The resultant filtrate is treated with saturated sodium bicarbonate and solid sodium bicarbonate with stirring until bubbling ceases. The organic layer is saved. The aqueous layer is extracted with methylene chloride. The combined organic layers are washed with saturated sodium bicarbonate, dried over anhydrous magnesium sulfate and concentrated in vacuo. The residue is stirred overnight in diethyl ether-methylene chloride to afford, after filtration, the title compound as a white solid (24.5 g, 79.0%, mp 101-103° C.) which is identified by NMR spectral analysis.

Provenance & Evidence