A metal-free C–H [5 + 1] annulation reaction of 2-arylanilines with diazo compounds has been achieved, giving rise to two types of prevalent phenanthridines via highly selective C–C cleavage. Compared to the simple N–H insertion manipulation of diazo, this method elegantly accomplishes a tandem N–H insertion/SEAr/C–C cleavage/aromatization reaction, and the synthetic utility of this new transformation is exemplified by the succinct syntheses of trisphaeridine and bicolorine alkaloids.
