Research On Visible-light-promoted C=C Bond/C-H Bond Involved Heterocyclization Reaction

Nitrogen-and oxygen-containing heterocyclic compounds are widely found in natrual products,pharmaceuticals and functional material molecules for the unique biological and chemical activity.The assembly of these compounds efficiently are still important in the field of organic synthesis.Alkenes are important petrochemical product and essential chemical materails which are widely existed and very active in organic reations.The establishment of heterocyclic compounds through nucleophilic addition of heteroatoms to alkenes has always aroused considerable interest but remains chanlleging for the negtive eletrophilicity of alkenes.The traditional methods to activate the carbon-carbon bond suffer from some inherent deficiencies such as environmentally unfriendly and unsafely factors.In recent years,the rapid development of visible light reaction has offerd powerful and mild platform for the construction of C-X bonds through single electron trasfer.Meawhile,visible light promoted C-H bond activation provided effective access to direct C-X bond constrction.In this dissertation,we focus on the activation of C=C and C-H bonds by visible light as an efficient approach to the carbon-heteroatom bond formation and developed some work as following.CBr₄ was served as an oxidative quencher and the electron rich olefin was oxidized to a radicl cation.That enabled the nucleophilic reaction of ketone carbonyl group with the C=C bond to give the furan compound with high efficiency and the yield was up to 99%.When CBr4 was added in excess,bromination reaction occurred with 100% region-selectivity due to the conjugated effect.The cyclopropyl ketones was regarded as perfect precursor to ?,?-unsaturated ketone by a series of control and isotopic tracing experiments,which improved the synthetic route well.The 5-exo cyclization of ?,?-unsaturated oxime ester was achieved by excited palladium complex under the irradiation of blue LEDs.The remaining carbon radical coupled with aryl olefins in the presence of palladium to accomplish the intermolecular Narasaka-Heck reaction,giving a pyrrolin compound with double active funtional groups.The pyrrolin could be transformed to a tricyclic compound processing a bridgehead nitrogen consist of the core skeleton of many alkaloids in40% yield over three simple steps,illustrating the practicality of the method.The strategy overcomes the restriction of the traditonal Narasaka-Heck reaction with 34 examples scope showing excellent adaptability.The iminyl nitrogen radical cyclization pathway was further supported by DFT caculations and the subsequent generation of hybrid alkyl radical/Pd species was detected by radical probe experiment.Based on the formation of iminyl nitrogen radicals promoted by visible light,a novel strategy to trap iminyl radicals with copper ions has been developed at room temperature,the resulted high-valent Cu(?)imine intermediate resets quickly to form nitrene and then to furnish a 2H-azirine.This protocol with dual copper/photoredox catalyst enables the selective imination of unactivated C-H bonds under mild conditions with a broader scope.The Stem-Volmer fluorescence quenching experiments further demonstrated the synergistic effect of dual copper and fac-Ir(ppy)3 containing a SET pathway and Cu(I)to Cu(?)cycle.The control experiment that an optically active substrate generated a racemic product supported the intermediacy of nitrene complex.