Silyl radical initiated radical cascade addition/cyclization: synthesis of silyl functionalized 4H-pyrido[4,3,2-gh]phenanthridin-5(6H)-ones.

A cyclization cascade initiated by the addition of a silyl radical to an electron-deficient carbon-carbon double bond of N-arylacrylamides, followed by intramolecular cyano group insertion and homolytic aromatic substitution has been reported. In the presence of di-lauroyl peroxide (LPO), under metal-free conditions, several readily available hydrosilanes were successfully used as the source of silyl radicals and a series of silyl functionalized 4H-pyrido[4,3,2-gh]phenanthridin-5(6H)-ones were obtained in moderate to good yields.