Carboxylate-Assisted Pd(II)-Catalyzed ortho-C–H and Remote C–H Activation: Economical Synthesis of Pyrano[4,3‑b]Indol-1(5H)‑ones

An original Pd­(II)-catalyzed domino two C–H activations strategy has been designed to synthesize pyrano­[4,3-b]­indol-1­(5H)-one motifs from inexpensive and commercially available olefins and heteroaromatic acids by carboxylate-directed sequential ortho-C–H alkenylation and remote C–H lactonization. Importantly, this protocol overcomes the selectivity for carboxylic acids with acrylates of the conventional Michael addition-type process. Preliminary studies of mechanism indicate that both aryl and olefinlic C–H activations may participate in this catalytic system.