p-Toluenesulfonic acid → Tert-butyl 8-benzyl-10-(2-pyridyl)-11-oxa-3,8-diazaspiro[5.5]undec-9-ene-3-carboxylate

Participants

Reaction Conditions

Reaction Steps

To tert-butyl 4-[[benzyl-[2-oxo-2-(2-pyridyl)ethyl]amino]methyl]-4-hydroxy-piperidine-1-carboxylate (190 mg, 0.43 mmol) in benzene (11 mL) was added 4-methylbenzenesulfonic acid (99 mg, 0.52 mmol) and reaction mixture was heated at 80° C. for 30 minutes. The reaction mixture was cooled, diluted with ethyl acetate and washed sequentially with sat. NaHCO3 and brine solution. The organic layer was separated, dried over Na2SO4, filtered and concentrated in vacuo to give residue, which was purified using silica gel column chromatography using EtOAc/DCM (10-100%) as eluent to give tert-butyl 8-benzyl-10-(2-pyridyl)-11-oxa-3,8-diazaspiro[5.5]undec-9-ene-3-carboxylate (86 mg, 45%). ESI-MS m/z calc. 421.5. found 422.2 (M+1)+; Retention time: 1.42 minutes (3 min run). 1H NMR (400 MHz, CDCl3) δ 8.40-8.34 (m, 1H), 7.56 (dd, J=4.0, 3.5 Hz, 1H), 7.37-7.27 (m, 6H), 7.07 (s, 1H), 6.92 (d, J=1.5 Hz, 1H), 4.22 (s, 2H), 3.99-3.76 (m, 2H), 3.17 (t, J=11.8 Hz, 2H), 2.78 (s, 2H), 1.83 (s, 2H), 1.44 (s, 9H), 1.40 (d, J=4.4 Hz, 2H).

Provenance & Evidence