Synthesis of 3-Azidopiperidine Skeleton Employing Ceric Ammonium Nitrate (CAN)-Mediated Regioselective Azidoalkoxylation of Enol Ether: Total Synthesis of D2 Receptor Agonist (±)-Quinagolide.

The total synthesis of (±)-quinagolide, which is a D2 receptor agonist, was accomplished via a ceric ammonium nitrate (CAN)-mediated regioselective azidoalkoxylation of enol ether route. Key features of the synthesis include Claisen rearrangement, PPTS (pyridinium p-toluenesulfonate)-catalyzed one-pot acetal deprotection, followed by a diastereoselective Henry reaction, which enables construction of the required trans ring junction and CAN-mediated regioselective azidoalkoxylation of enol ether. The PPTS-catalyzed intramolecular diastereoselective Henry reaction to fix three contiguous stereocenters on tetrahydronaphthalene and the first-of-its-kind synthesis of the 3-azidopiperidine skeleton, using a CAN-mediated regioselective azidoalkoxylation of enol ether, are important findings of the present work.