反应详情

The starting compound was prepared by conversion of 5-methoxy-benzisothiazole-3(2H)-one-1,1-dioxide, analogous to 5-methyl-benzisothiazole-3(2H)-one-1,1-dioxide (see Example 8), with sodium hydroxide and methyl chloroacetate into methyl 5-methoxy-3-oxo-benzisothiazolo-2(3H)-acetate-1,1-dioxide. Methyl 4-hydroxy-6-methoxy-2H-1,2-benzothiazine-3-carboxylate-1,1-dioxide (m.p. 183° C., from ethyl acetate/cyclohexane) was obtained by subsequent rearrangement with sodium methylate in toluene/tert. butanol, and methyl 4-hydroxy-6-methoxy-2-methyl-2H-1,2-benzothiazine-3-carboxylate-1,1-dioxide was obtained by subsequent methylation.