Pyridine → 1,1-Dimethylethyl 3-{[(5-chloro-2-thienyl)sulfonyl]amino}-4-(methyloxy)-1H-indazole-1-carboxylate

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Reaction Steps

To a solution of 1,1-dimethylethyl 3-amino-4-(methyloxy)-1H-indazole-1-carboxylate (for a preparation see Intermediate 5) (6.03 g, 22.9 mmol) and 5-chloro-2-thiophenesulfonyl chloride (3.07 mL, 22.9 mmol) in DCM (30 mL) was added dropwise at 0° C. a solution of pyridine (3.7 mL, 46 mmol) in DCM. The reaction mixture was stirred allowing to warm from 0° C. to room temperature over 2 h, then stirred at room temperature over the weekend. Pyridine (50 mL) were added and resulting mixture was stirred at 50° C. for another 24 h. The reaction mixture was then quenched with 50 mL of a saturated NaHCO3 solution. The organic layer was partitioned and the aqueous layer was further extracted with 50 mL of DCM. The organic solutions were combined, washed with water (50 mL) then brine (50 mL), and dried with an hydrophobic frit. The crude product was purified by chromatography on two 100 g Si cartridges on Flashmaster, eluting with 0 to 25% gradient of EtOAc in DCM, over 60 min to give the desired product as a pale orange solid: (2.21 g, 22%). LCMS (System A) RT=1.35 min, ES+ve m/z 444 (M+H)+.

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