A solution of piperazine-1-carboxylic acid phenylamide (103 mg) and 2-naphthaldehyde (94 mg) in DCM (2 mL) was treated with NaB(OAc)3H (148 mg). After 16 h, the resulting mixture was treated with 10% aq. KOH (2 mL). The aqueous phase was extracted with DCM (2×3 mL). The combined extracts were dried (MgSO4) and concentrated. Chromatography of the residue gave the title compound as a white foam (111 mg). 1H NMR (400 MHz, CDCl3): 7.85-7.80 (m, 3H), 7.74 (s, 1H), 7.52-7.45 (m, 3H), 7.35-7.25 (m, 4H), 7.05-7.00 (m, 1H), 6.37 (br s, 1H), 3.69 (s, 2H), 3.53-3.48 (m, 4H), 2.55-2.49 (m, 4H).
