GENERAL METHOD: A suspension of methyl 3-iodo-4-aminobenzoate (1 mmol), methyl thioglycolate (1.5 eq.), cuprous(I) iodide (0.05 mmol), trans-N,N'-dimethylcyclohexane-1,2-diamine (0.1 mmol), and cesium carbonate (2 eq.) in anhydrous 1,4-dioxane (4 mL) was added to a vial. Nitrogen was passed into the suspension to degas it for 3 min under stirring. Subsequently, the vial was sealed. The reaction mixture was heated at 100 °C (oil bath temperature) for 15 hours. After completion of the reaction, it was cooled to room temperature and filtered. The filtrates were combined and concentrated using a rotary evaporator and the resulting residue was purified by silica gel column chromatography (eluent: 5% dichloromethane solution in methanol) to afford the target product, methyl 3-carbonyl-3,4-dihydro-2H-1,4-benzothiazine-6-carboxylate, as a beige solid.
