Synthesis of Enantioenriched 2‑Alkyl Piperidine Derivatives through Asymmetric Reduction of Pyridinium Salts

An Ir-catalyzed enantioselective hydrogenation of 2-alkyl-pyridines has been developed using ligand MeO-BoQPhos. High levels of enantioselectivities up to 93:7 er were obtained. The resulting enantioenriched piperidines can be readily converted into biologically interesting molecules such as the fused tricyclic structures <b>5</b>, <b>6</b>, and <b>7</b> in 99:1 er, providing a novel, concise synthetic route to this family of chiral piperidine-containing compounds