Triethylamine → [(S)-2-((S)-8-Azidomethyl-7,8-dihydro-[1,4]dioxino[2,3-g]indazol-1-yl)-1-methyl-ethyl]-carbamic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

To a 0° C. stirred solution of the alcohol from Step A (0.69 g, 1.87 mmol) in anhydrous tetrahydrofuran (30 mL) was added triethylamine (0.38 g, 0.52 mL, 3.7 mmol) and methanesulfonic anhydride (0.49 g, 2.81 mmol) under a nitrogen atmosphere. After 1 h the volatiles were evaporated. To the residue was added anhydrous DMSO (40 mL) and sodium azide (2.43 g, 37 mmol). The resulting mixture was heated at 90° C. for 1 h, cooled, mixed with a saturated aqueous solution of sodium bicarbonate (100 mL) and extracted with ethyl acetate (50 mL×3). Chromatography on silica eluting with a gradient of 0% to 25% ethyl acetate/hexane gave an oil (0.65 g, 88%), that solidified on standing. Crystallization from ethyl acetate/hexane gave a crystalline solid (0.48 g, 65%): mp 134-135° C. LCMS (+APCI) 395 (M+H).

Provenance & Evidence