Trifluoroacetic acid → tert-Butyl 4-(5-fluoro-6-nitro-1-oxoisoindolin-2-yl)piperidine-1-carboxylate

참여 물질

반응 단계

tert-Butyl 4-(4-fluoro-5-nitro-2-vinylbenzamido)piperidine-1-carboxylate (Step 2, 1.1 g, 2.77 mmol) in 50 mL of DCM is chilled to −78° C. Ozone was passed through the solution until the starting material was consumed, and then nitrogen was passed through the solution for 5 min. The reaction mixture was warmed to room temperature. Triphenylphosphine-resin (2.77 g) in 10 mL of DCM was added, and was stirred for another 1.5 h. The resin was filtered off, and the solution was concentrated in vacuo. The resulting crude was dissolved in DCM (15 mL), and to this solution were added TFA (15 mL) and triethylsilane (1.0 mL, 5.9 mmol) sequentially. The reaction was stirred at room temperature 2 h. After concentration, the reaction crude was poured into 10 mL of water, neutralized to pH 8 with sat. aq. NaHCO3, followed by addition of (Boc)2O (603 mg, 2.77 mmol) in 10 mL of DCM. The reaction was stirred at room temperature for 1.5 h, then extracted with DCM. The organic extracts were dried (Na2SO4), concentrated in vacuo, and purified by silica gel chromatography (EtOAc/Hexanes:1/4) to give tert-Butyl 4-(5-fluoro-6-nitro-1-oxoisoindolin-2-yl)piperidine-1-carboxylate; ESMS m/z 380.2 (M+H+).

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