Cobalt‐Catalyzed C8‐Dienylation of Quinoline‐<i>N</i>‐Oxides
Rahul K. Shukla, Akshay M. Nair, Salman Khan, Chandra M. R. Volla
Abstract
Abstract An efficient Cp*Co III ‐catalyzed C8‐dienylation of quinoline‐ N ‐oxides was achieved by employing allenes bearing leaving groups at the α‐position as the dienylating agents. The reaction proceeds by Co III ‐catalyzed C−H activation of quinoline‐ N ‐oxides and regioselective migratory insertion of the allene followed by a β‐oxy elimination, leading to overall dienylation. Site‐selective C−H activation was achieved with excellent selectivity under mild reaction conditions, and 30 mol % of a NaF additive was found to be crucial for the efficient dienylation. The methodology features high stereoselectivity, mild reaction conditions, and good functional‐group tolerance. C8‐alkenylation of quinoline‐ N ‐oxides was achieved in the case of allenes devoid of leaving groups as coupling partners. Furthermore, gram‐scale preparation and preliminary mechanistic experiments were carried out to gain insights into the reaction mechanism.