Development of a scaleable route for the production of cis-N-benzyl-3-methylamino-4-methylpiperidine

The synthesis of cis-N-benzyl-3-methylamino-4-methylpiperidine (5) via hydroboration of tetrahydropyridine 3 followed by oxidation and reductive amination was optimized and scaled up to produce 10-kg quantities of product. Three routes to 3 were identified, and the reduction of pyridinium salt 7 was selected as the most preferable to run on-scale. The hydroboration and oxidative workup were carefully studied to optimize throughput on that transformation, as was the reductive amination.