Enal Transfervia Piano-Stool Rh-Enalcarbenoids: RapidConstruction of Enal-Functionalized Isoquinolones, Application TowardBenzo[<i>c</i>]phenanthridinone Scaffolds

Herein, we disclosed a Rh-catalyzed site-selective enal transfer reaction of benzamides with diazoenals leading to multisubstituted enal-functionalized isoquinolone derivatives. The reaction involves arene <i>ortho</i> C–H activation, migratory insertion of a new class of <i>N</i>-heterocyclic Piano-stool Rh-enalcarbenoid, and metal-templated cyclization. The synthetic utility of enal-functionalized isoquinolones has been demonstrated by the short synthesis of valuable benzo[<i>c</i>]phenanthridinone scaffolds, which are present in many naturally occurring alkaloids with broad pharmacological properties and an analogue of oxyavicine natural product used for ophthalmic disorders.