I2-Triggered N-O cleavage of ketoxime acetates for the synthesis of 3-(4-pyridyl)indoles.

A facile and complementary [3 + 2 + 1] annulation of aryl ketoxime acetates and 3-formylindoles to give pyridine derivatives is reported. The condensation reaction demonstrated that I2 was capable of triggering N-O bond cleavage of ketoxime acetates to generate iminyl radicals via a single electron transfer pathway. This direct and operationally simple protocol provides a fundamental platform to synthesize 3-(4-pyridyl)indoles with high functional group compatibility and high regioselectivity.