N-(Acyloxy)phthalimides as tertiary alkyl radical precursors in the visible light photocatalyzed tandem radical cyclization of N-arylacrylamides to 3,3-dialkyl substituted oxindoles†
Abstract
A visible light promoted tandem radical cyclization of N-arylacrylamides with N-(acyloxy)phthalimides to 3,3-dialkyl substituted oxindoles was developed. In the presence of a photocatalyst Ru(bpy)3Cl2·6H2O, an organic base i-Pr2NEt and the irradiation of a 25 W compact fluorescence bulb at room temperature, N-(acyloxy)phthalimides may be used as a masking group for tertiary alkyl radicals. This tandem radical reaction proceeded smoothly to afford the 3,3-dialkyl substituted oxindoles at room temperature and avoided the use of peroxide.