Trifluoroacetic acid → 1-Benzyl-4-(piperidin-4-ylcarbonyl)piperazine

A solution of 1-benzyl-4-[(1-t-butoxycarbonyl-4-piperidyl)carbonyl]piperazine (115.7 g) in dry dichloromethane (222 ml) was added dropwise over 45 minutes to trifluoroacetic acid (575 ml), maintaining the temperature below 25° C. under an atmosphere of argon. The solution was stirred at 23-25° C. for 1 hour. The solution was evaporated using a bath temperature of 30° C. The residual oil was poured, in portions, into saturated aqueous sodium carbonate solution (770 ml) while maintaining the temperature below 30° C. The aqueous mixture was extracted with dichloromethane (3×575 ml). The dichloromethane extracts were combined, dried (Na2SO4) and evaporated to give 1-benzyl-4-[(4-piperidyl)carbonyl]piperazine (56.2 g, 65% yield) as a white solid;