Trifluoroacetic acid → ethyl 3-(2,3-dihydro-1H-spiro[isoquinoline-4,4'-piperidine]-1'-yl)-8-azabicyclo[3.2.1]octane-8-carboxylate

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Reaction Steps

The crude tert-butyl 1′-(8-(ethoxycarbonyl)-8-azabicyclo[3.2.1]octan-3-yl)-1H -spiro[isoquinoline-4,4′-piperidine]-2(3H)-carboxylate 5b (3.641 g) was dissolved in dichloromethane (10 mL) and treated with trifluoroacetic acid (10 mL). The reaction was stirred at room temperature for 45 min, then concentrated under reduced pressure. The oil obtained was re-dissolved in acetonitrile, re-concentrated under reduced pressure, treated with 2 N NaOH (25 mL) and extracted with dichloromethane (2×50 mL). The combined extracts were washed with saturated NaHCO3, saturated brine, dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure to afford 2.55 g crude ethyl 3-(2,3-dihydro-1H-spiro[isoquinoline-4,4′-piperidine]-1′-yl)-8-azabicyclo[3.2.1]octane-8-carboxylate 5c as a pale yellow oil, which solidified upon standing overnight at room temperature. LC/MS m/z [M+H]+ 384.2 retention time 1.34 min (10-99% CH3CN—H2O gradient, with 0.05% TFA, 5 min). 1H-NMR (400 MHz, CDCl3) δ 7.60 (d, J=8.0 Hz, 1H), 7.29 (t, J=7.3 Hz, 1H), 7.19 (t, J=7.4 Hz, 1H), 7.07 (d, J=7.5 Hz, 1H), 6.06 (br s, 2H), 4.37 (br s, 2H), 4.25 (s, 2H), 4.12 (q, J=7.1 Hz, 2H), 3.47 (m, 3H), 3.24 (m, 2H), 2.93 (m, 2H), 2.53 (m, 2H), 1.96 (m, 8H), 1.71 (m, 2H), 1.26 (t, J=7.1 Hz, 3H).

Provenance & Evidence