Iodine-promoted amide formation via oxidative cleavage of indoles: novel quinazoline-4(3H)-one and tryptanthrin syntheses.

A highly efficient method for the direct construction of amide bonds via a selective cleavage of C-H and C[double bond, length as m-dash]C bonds in indole structures using an iodine-promoted approach was developed. Mechanistic studies indicated the formation of superoxide radicals obtained from molecular oxygen activation as a key intermediate step, which provided a precursor for subsequent oxidative ring-opening and intermolecular cyclization. A broad range of quinazolin-4(3H)-ones and tryptanthrins were synthesized in moderate to good yields under mild and environmentally benign conditions.