Di-tert Butyl Peroxide-Promoted Sequential Methylation and Intramolecular Aromatization of Isonitriles

The di-tert butyl peroxide (DTBP)-promoted sequential reaction of isonitriles is developed, leading to 6-methylphenanthridine derivatives in moderate to excellent yields. DTBP served as both promoter and methyl source. The procedure proceeds through the addition of a methyl radical derived from the peroxide to the isonitrile followed by aromatic homolytic cyclization. It tolerates a series of functional groups, such as fluoro, chloro, acetyl, methoxycarbonyl, cyano and trifluoromethyl.