Benzyl (4-oxocyclohexyl)carbamate → (6-Cyano-2,3,4,9-tetrahydro-1H-carbazol-3-yl)-carbamic acid benzyl ester

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Reaction Steps

Combine 4-cyanophenylhydrazine hydrochloride (27.4 g, 162 mmol) and (4-oxo-cyclohexyl)-carbamic acid benzyl ester (Preparation 42) (40.0 g, 162 mmol) in acetic acid (800 mL). Heat the reaction to 90° C. overnight, then cool to room temperature and concentrate under reduced pressure. Triturate the residue in dichloromethane and discard the filter cake. Concentrate the filtrate under reduced pressure. Purify the resulting residue by flash chromatography (silica gel, 9:1 chloroform:acetone). Recrystillize the resulting material from benzene to provide 38.8 g (69%) of the title compound. m.p.=141-143° C.; mass spectrum (m/e): 344 [C21H19N3O2−1]−; 1H NMR (300 MHz, CDCl3): δ 8.15 (s, 1H), 7.73 (s, 1H), 7.29-7.38 (m, 7H), 5.12 (s, 2H), 4.89-4.92 (m, 1H), 4.18 (m, 1H), 3.09 (dd, J=5.0, 15.5 Hz, 1H), 2.78-2.91 (m, 2H), 2.59 (dd, J=7.0, 15.5 Hz, 1H), 2.07-2.17 (m, 1H), 1.93-2.05 (m, 1H).

Provenance & Evidence