Study On The Synthesis Of Benzimidazo[2,1-a]isoqui-Nolin-6(5h)-ones By Vanadium Catalysis

Benzimidazo[2,1-a]isoquinolin-6(5H)-ones have received widespread attention due to their unique structural properties and their potentially biological activities.Compared with the well-established late-transition metals,the benzimidazo[2,1-a]isoquinolin-6(5H)-ones synthesis through early-transition metal catalysis remained largely lagged behind.Vanadium is an earth-abundant early transition metal and the low-valent vanadium-based organometallic catalysis remained rarely investigated,although many well-defined vanadium complexes are extensively used for alkene polymerization and oxidation.Thus,the development of low-valent vanadium catalysis on benzimidazo[2,1-a]isoquinolin-6(5H)-ones synthesis remains a desirable and challenging goal.Based on our previous work,we use the benzene-bridged low-valent divanadium complex(?-?⁶:?⁶-C₆H₆)[V(Nacnac)]₂as catalyst for the reaction between N-methacryloyl-2-arylbenzoimidazoles and hypervalent iodine(III)reagents(HIRs),this transformation can generate a series of structurally diverse tetracyclic benzimidazo[2,1-a]isoquinolin-6(5H)-ones with high regioselectivity and excellent functional-group tolerance.This dissertation contains the following work:(1)Benzimidazo[2,1-a]isoquinolin-6(5H)-ones synthesis from the reaction between N-methacryloyl-2-arylbenzoimidazoles and HIRs enabled by low divanadium complex(?-?⁶:?⁶-C₆H₆)[V(Nacnac)]₂.(2)Preliminary mechanism experiment revealed that an intermolecular radical alkylation,intramolecular radical cyclization and oxidative re-aromatization cascade may occur in the reaction.(3)Characterization of benzimidazo[2,1-a]isoquinolin-6(5H)-ones and synthesis ofsubstrates.