Ligand-Enabled [3+2] Annulation of Aromatic Acids with Maleimides by C(sp )-H and C(sp )-H Bond Activation.

A palladium-catalyzed [3+2] annulation of substituted benzoic acids with maleimides leading to tricyclic heterocyclic molecules having a free carboxylic group in a high atom- and step-economical manner is described. The reaction proceeds via a dual C-H bond activation such as C(sp )-H at the benzylic position and C(sp )-H bond activation at the meta position of substituted aromatics. An external ligand (MPAA) is crucial for the success of present protocol. Further, the decarboxylation and esterification of the free carboxylic acid group of observed products were carried out.