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

An original Pd(II)-catalyzed domino two C-H activations strategy has been designed to synthesize pyrano[4,3- b]indol-1(5 H)-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.