4-Toluenesulfonyl chloride → (2R,5R)-5-Azidomethyl-4-[2-(6-chloro-3,3-dimethyl-2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-2-methyl-piperazine-1-carboxylic acid tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

(2R,5R)-4-[2-(6-Chloro-3,3-dimethyl-2,3-dihydro-indol-1-yl)-2-oxo-ethyl]-5-hydroxymethyl-2-methyl-piperazine-1-carboxylic acid tert-butyl ester (175 mg, 0.39 mmol) was dissolved in anhydrous DCM (3.87 mL) and cooled in an ice bath. Triethylamine (0.27 mL, 1.94 mmol) was added followed by toluene-4-sulfonyl chloride (148 mg, 0.77 mmol). Reaction was stirred for 1 h at 0° C. (ice bath) and gently warmed to ambient temperature over 18 h. The solvent was removed in vacuo and residue purified by column chromatography on silica gel (0-50%, EtOAc/petrol). The product (117 mg, 0.25 mmol) was dissolved in DMF (2.5 mL) and sodium azide (24 mg, 0.37 mmol) added. The reaction was heated to 65° C. for 18 h, then cooled to ambient temperature and the solvent removed in vacuo. The residue was slurried in Et2O, filtered and the filtrate evaporated in vacuo. The resulting oil was purified by column chromatography on silica gel (gradient elution, 0-75%, EtOAc/petrol), to give the title compound (81 mg, 44%) as a colourless oil. 1H NMR (Me-d3-OD): 8.14 (1H, d), 7.21 (1H, d), 7.09 (1H, dd), 4.26-4.15 (1H, m), 4.10-3.97 (3H, m), 3.76-3.46 (3H, m), 3.46-3.36 (1H, m), 3.05-2.91 (1H, m), 2.85 (1H, dd), 2.70 (1H, dd), 1.50 (9H, s), 1.38 (6H, s), 1.24 (3H, d).

Provenance & Evidence