A solution of 1-t-butoxycarbonyl-3-piperidinecarboxylic acid (458 mg, 2.00 mmol), sodium hydride (88 mg, 2.20 mmol, 60% oil suspension), oxalyl chloride (0.22 ml, 2.50 mmol) and catalytic amount of dimethylformamide (0.20 ml) in dichloromethane (16 ml) was stirred at 0° C. After stirring for 30 min, aniline (0.20 ml, 2.20 mmol) which was treated with n-butyl lithium (1.45 ml, 2.30 mmol, 1.59 M in hexane) in tetrahydrofuran (4 ml) was added to the reaction mixture at 0° C. After additional 30 min, saturated ammonium chloride was added and the whole reaction mixture was extracted with ethyl acetate. The organic layer was washed with brine, dried over Na2SO4 and evaporated in vacuo. Purification of the residue by silica gel column chromatography (hexane-ethyl acetate) gave 1-t-butoxycarbonylpiperidine-3-carboxanilide (437 mg, 71%).
