Selective C-O Bond Forming Reactions at Indole-C2-Position toward Polycyclic Indolone or Indolinone Derivatives Tethered with Medium-Sized Rings.

A methodology involving the chemoselective synthesis of tetracyclic [1,3]oxazino[3,2- a ]indol-4-one or tetracyclic [1,3]oxazino[3,2- a ]indoline-4-one tethered with a medium-sized ring by cross dehydrogenative coupling (CDC) or nucleophilic addition (NA) reaction has been developed. [1,3]Oxazino[3,2- a ]indol-4-one compounds fused with a medium-sized ring were constructed through a CDC reaction in the presence of I 2 and K 2 CO 3 . Whereas, [1,3]oxazino[3,2- a ]indoline-4-ones tethered with a medium-sized ring were obtained with a TfOH system by NA reaction.