Hydrochloric Acid → Benzyl 4-(4-aminophenyl)piperazine-1-carboxylate

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Reaction Steps

To a mixture of benzyl 4-(4-nitrophenyl)piperazine-1-carboxylate (I3) (1.11 g, 3.25 mmol) and CoCl2 (0.844 g, 6.50 mmol) in MeOH (30 mL) was added NaBH4 (1.23 g, 32.5 mmol) portion-wise at 0° C. Stirring was continued at 0° C. for 1 hour before aqueous 3 M HCl (10 mL) was added. The mixture was concentrated in vacuo to remove the MeOH and the aqueous layer was extracted twice with diethyl ether. The aqueous layer was basified with 1 M aqueous NaOH and extracted twice with EtOAc. The combined organic extracts were dried (MgSO4), concentrated in vacuo, then adsorbed onto silica gel and purified by silica gel column chromatography (Biotage Isolera, 12 g SiO2 cartridge, 50-60% EtOAc in hexanes) to give the title compound K2 as a purple solid (397 mg, 39%); 1H NMR (400 MHz, CDCl3) δ 7.40-7.29 (m, 5H), 6.83-6.78 (m, 2H), 6.68-6.62 (m, 2H), 5.16 (s, 2H), 3.70-3.61 (m, 4H), 3.46 (s, 2H), 3.10-2.86 (m, 4H). LCMS-A: rt 4.650 min; m/z 312.1 [M+H]+.

Provenance & Evidence