Sulfuric Acid → HCID 66686367, compound

Participants

Reaction Steps

A suspension of methyl 7-tert-butylcarbonylamino-4H-chromeno[3,4-d]isothiazole-6-carboxylate (Intermediate 75, 0.690 g) in methanol (30 mL) was treated with concentrated sulfuric acid (1.2 mL) and the resultant mixture was heated at 75° C. in a sealed vessel overnight. The mixture was cooled, diluted with ethyl acetate and washed with saturated aqueous sodium bicarbonate solution. The aqueous phase was saturated with sodium chloride then extracted with ethyl acetate again. The combined organic layers were dried (Na2SO4), filtered and the filtrate was concentrated in vacuo. The residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane, with a gradient of 15-45% to give methyl 7-amino-4H-chromeno[3,4-d]isothiazole-6-carboxylate (0.345 g) as a yellow solid.

Provenance & Evidence