A mixture of tert-butyl 5-(aminomethyl)-4-chloro-1H-indole-1-carboxylate (1.147 g, 4.087 mmol) and benzophenone imine (0.75 mL, 4.496 mmol) in anhydrous DCM (39.3 mL) was stirred at 40° C. under N2 for 4 d. The reaction mixture was diluted with EtOAc, and the organic layer was washed with water and brine, dried (Na2SO4), filtered, and concentrated in vacuo. The crude product was purified by SiO2 chromatography eluting with and EtOAc/heptane gradient (0 to 70% EtOAc) to afford 1.22 g (67%) of tert-butyl 5-[(benzhydrylideneamino)methyl]-4-chloro-1H-indole-1-carboxylate (322) as an oil: 1H NMR (400 MHz, CDCl3) δ 8.01 (d, J=8.5 Hz, 1H), 7.82-7.77 (m, 1H), 7.69 (d, J=7.2 Hz, 2H), 7.60-7.56 (m, 1H), 7.48 (d, J=8.2 Hz, 1H), 7.43 (d, J=8.9 Hz, 2H), 7.37 (d, J=7.0 Hz, 1H), 7.33 (t, J=7.3 Hz, 2H), 7.25-7.20 (m, 2H), 6.66 (d, J=3.7 Hz, 1H), 4.75 (s, 2H), 1.66 (s, 9H); MS (ESI) m/z=445.2 [M+1]+.
