Benzo[d][1,3]Oxazine‐Assisted C─H Annulation of Arenes with Diarylacetylenes: Access to 3,4‐diarylisoquinolinones

A novel Rh(III)‐catalyzed [4 + 2] annulation of diarylacetylenes with 2‐aryl‐4 H ‐benzo[ d ][1,3]oxazines is described to produce a new class of 3,4‐diarylisoquinolinones through a ring‐opening C─H annulation of benzo[ d ][1,3]oxazine moiety. This is the first report on C─H functionalazation of 2‐aryl‐4H‐benzo[ d ][1,3]oxazines with diarylalkynes for the synthesis of 3,4‐diarylisoquinolinone scaffolds. The scope of this method is well exemplified with diverse substrates bearing different functional groups including electron‐rich and electron‐deficient substituents.