Pd/LA-catalyzed decarboxylation enabled exclusive [5+2] annulation toward N-aryl azepanes and DFT insights

A practical and straightforward methodology towards the synthesis of non-fused N-aryl azepane derivatives with diversity is described. These Pd/LA-catalyzed reactions proceed smoothly under extremely mild conditions with ample reaction scope and CO2 as the byproduct. The resulting products can be easily converted into a range of highly functionalized azepanes. The synthetic value of this protocol is further proved in the formal synthesis of a pharmaceutically relevant Proheptazine derivative. DFT calculations revealed the details of the reaction pathway and the origin of this unusual exclusive [5 + 2] rather than empirical [3 + 2] annulation process.

Automated summary

A practical and straightforward methodology for synthesizing non-fused N-aryl azepane derivatives with diversity has been described. The reactions proceed smoothly under mild conditions with CO2 as a byproduct, and the resulting products can be easily converted into a range of highly functionalized azepanes. The DFT calculations reveal the details of the reaction pathway and the origin of the unusual exclusive [5 + 2] annulation process.