p-Toluenesulfonic acid monohydrate → ethyl (8-methyl-1,1-dioxido-4H-[1,3]oxazolo[5,4-h][1,2,4]benzothiadiazin-3-yl)acetate

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Reaction Steps

A solution of the product of Example 352E (56.3 mg, 0.188 mmol) in anhydrous N,N-dimethylformamide (2 mL) was treated with trimethylorthoacetate (0.098 mL, 0.752 mmol) and p-toluenesulfonic acid monohydrate (1Mg) at room temperature for 3 hours under a nitrogen atmosphere. The solvent was removed under reduced pressure and the residue purified by column chromatography on silica gel eluting with 4% methanol/dichloromethane to give the title compound as a white crystalline solid (48 mg, 79%). MS (ESI−) m/z 322 (M−H)−. 1H NMR (300 MHz, DMSO-d6) δ 1.22 (t, J=7.17 Hz, 3 H) 2.69 (s, 3 H) 3.71 (s, 2 H) 4.17 (q, J=7.11 Hz, 2 H) 7.27 (d, J=8.82 Hz, 1 H) 8.02 (d, J=8.82 Hz, 1 H) 12.33 (s, 1 H).

Provenance & Evidence