Triethylamine → tert-butyl N-tert-butoxycarbonyl-N-[3-[3-[4-(chloromethyl)phenyl]isoxazol-5-yl]-5-(4-isopropylsulfonylphenyl)pyrazin-2-yl]carbamate

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Reaction Steps

Triethylamine (899.0 mg, 1.238 mL, 8.884 mmol) was added to a solution of tert-butyl N-tert-butoxycarbonyl-N-[3-ethynyl-5-(4-isopropylsulfonylphenyl)pyrazin-2-yl]carbamate 8 (4.05 g, 8.074 mmol) and 4-(chloromethyl)-N-hydroxy-benzimidoyl chloride (2.063 g, 8.494 mmol) in DCM (12 mL). The mixture was stirred at RT for 22 h then partitioned between DCM and an ice/water solution. The combined organic extract was dried over MgSO4 and concentrated under reduced pressure then purified by chromatography on silica gel (eluent 30-50% EtAc/petrol) yielding tert-butyl N-tert-butoxycarbonyl-N-[3-[3-[4-(chloromethyl)phenyl]isoxazol-5-yl]-5-(4-isopropylsulfonylphenyl)pyrazin-2-yl]carbamate as colourless crystals (4.53 g, 79%). 1H NMR (400 MHz, CDCl3) δ 1.41 (18H, s), 4.66 (2H, s), 7.37 (1H, s), 7.54 (2H, d, J=8.0 Hz), 7.90 (2H, d, J=8.0 Hz), 8.66 (1H, s)

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