Synthesis of rimonabant

Objective: To optimize the synthetic route of rimonabant. Methods: Rimonabant hydrochloride was synthesized from 4-chloropropiophenone as starting material by silylation, acylation with ethyl oxalyl chloride to give α-γ-diketo ester, which was subjected to hydrazone reaction, cyclization, hydrolysis, amidation and salt formation. Results: The structure of the target compound was confirmed by MS, ¹HNMR, element analysis, and the overall yield was up to 34.2%. Conclusion: This synthetic route is of mild reacting condition, easy operation and relative high yield and is worthy to be pilot.