Reaction Steps
A solution of the (3aR,9bS)-1,3a,4,9b-tetrahydrospiro[benzo[g]indole-5,4′-piperidin]-2(3H)-one (900 mg, 3.51 mmol) in dichloromethane (100 ml) was treated with triethylamine (3 ml) and di-tert-butyl carbonate (1.5 g, 6.8 mmol) at room temperature for 1 h. The reaction mixture was diluted with dichloromethane, washed with aqueous saturated NH4Cl. The organic phase was separated and the aqueous phase was re-extracted with dichloromethane (2×). The combined organic phases were dried (Na2SO4), filtered and concentrated. The residue was purified by flasj chromatography (40 g silica gel, CH2Cl2/CH3CN up to 0:100%) to give (3aR,9bS)-tert-butyl 2-oxo-1,2,3,3a,4,9b-hexahydrospiro[benzo[g]indole-5,4′-piperidine]-1′-carboxylate 12 (700 mg). LC-MS: m/e=301.5 (M−t-Bu+H, 100%). Rt=3.04 min. 1H NMR (300 MHz, CDCl3): 7.36 (d, 1H), 7.25 (td, 1H), 7.21-7.13 (m, 2H), 6.32 (s, 1H, NH), 4.71 (d, J=5.8 Hz, 1H, CHN), 4.02 (br. d, 1H), 3.90 (br. d, 1H), 3.01 (td, J=13.4, 2.8 Hz, 1H), 2.89 (td, J=13, 3.1 Hz, 1H), 2.73-2.62 (m, 1H), 2.29 (td, J=12.7, 5.0 Hz, 1H), 2.23-2.44 (m, 3H), 1.66-1.59 (m, 1H), 1.51 (dd, J=13.2, 4.3 Hz, 1H), 1.41 (s, 9H), 1.37-1.30 (m, 2H).
