Photochemical Decarboxylative Radical Alkylation/Cyclization Reaction to Fused Nitrogen Heterocycles by LiI/PPh3 Catalysis

Abstract

A visible-light-induced decarboxylative radical cascade cyclization reaction between N-(2-cyanoaryl)-acrylamides and alkyl N-(acyloxy)phthalimide (NHPI esters) for the construction of phenanthridine derivatives has been developed. This approach utilizes lithium iodide (LiI) and triphenylphosphine (PPh₃) as the redox catalysts and the alkyl radical is produced through the photoactivation of the electron donor-acceptor (EDA) complex. A series of primary, secondary, and tertiary alkyl-substituted phenanthridines are prepared in up to 82% yield without transition-metal catalysts, chemical oxidants, or metal-/organic dye-based photocatalysts.