2,1-BENZOTHIAZINE 2,2-DIOXIDES. 9*. ALKYLATION OF METHYL 4-HYDROXY-1-METHYL-2,2-DIOXO- 1Н-2λ 6 ,1-BENZOTHIAZINE-3-CARBOXYLATE WITH

The alkylation of methyl 4-hydroxy-1-methyl-2,2-dioxo-1Н-2λ 6 ,1-benzothiazine-3-carboxylate in DMSO or acetone with ethyl iodide at 25°С gave a mixture of 3-ethyl- and 4-ethoxy-substituted derivatives, in complete agreement with quantum-chemical calculations. The ratio of С- and О-alkylation products changed depending on the alkali metal carbonate used as a base. The reaction practically did not proceed in anhydrous THF or water due to the low nucleophilicity of the anion.