A Photochemical Intramolecular C–N Coupling Toward the Synthesis of Benzimidazole-Fused Phenanthridines
Shyamal Kanti Bera, Palash Jyoti Boruah, Shraddha Saraswati Parida, Amit Kumar Paul, Prasenjit Mal
Abstract
Herein, we report a direct photochemical dehydrogenative C–N coupling of unactivated C(sp2)–H and N(sp2)–H bonds. The catalysts or additive-free transformation of 2-([1,1′-biphenyl]-2-yl)-1H-benzo[d]imidazole to benzo[4,5]imidazo[1,2-f]phenanthridine was achieved at ∼350 nm of irradiation via ε-hydrogen abstraction. DFT calculations helped to understand that the N–H···π interaction was essential for the reaction to proceed at a lower energy than expected.
Topics & Concepts
PhenanthridineChemistryIntramolecular forceBenzimidazoleImidazoleBiphenylHydrogen atom abstractionPhotochemistryStereochemistryMedicinal chemistryHydrogenOrganic chemistryCatalytic C–H Functionalization MethodsRadical Photochemical ReactionsSulfur-Based Synthesis Techniques