Visible-Light-Induced Carbon-Centred Radical Cascade For The Synthesis Of Oxygen-and Nitrogen-Containing Heterocycles

Oxygen-and nitrogen-containing heterocycles are widespread in some significant nature products,bioactive and pharmaceutical molecules.So the synthesis of those heterocycles is a longstanding interest for organic synthetic chemists.Moreover,visible light serves as a clean,sustainable energy source.Over the past decade,visible-light-induced photoredox catalysis has gained a considerable attention for organic chemists and rapid development.Among,the visible light-induced radical cascade reactions which enable an atom-and step-economic process,provide a mild and effective strategy to produce various reactive radicals for initiating radical reactions and assembly of diverse carbocyclic and heterocyclic skeletons.In this dissertation,recent advances in this area were reviewed and visible-light-induced carbon-centred radical addition cascade reactions for construction of oxygen-and nitrogen-containing heterocycles were investigated.The detailed research works are listed as below:First,we found that the chroman-2-one skeletons are an important family of oxygen-containing heterocycles,which always exist in bioactive and pharmaceutical molecules.And the hydrazides also are a significant structural motif.Because of their fascinating biological profiles,we have developed a visible-light-induced a-amino radical addition cascade of aroylhydrazones,for the grafting of the above "two privileged scaffolds".And then,we applied this strategy for the synthesis of a series of hydrazide-containing chroman-2-ones and dihydroquinolin-2-ones.Furthermore,we have gained the y-lactam and ?-lactam which show significant biological activities through different substrates and reaction condition.Based on control experiments and calculations of quantum yield,a possible mechanism was proposed.Then,when we utilized carbon-centred radicals with different electronic properties,we found that they exhibted different chemoselectivity for addition to activated or unactivited alkenes.So,we choosed the neutral alkyl radical derived from carboxylic acid,and applied for radical chemoselective addition cascade to o-vinyl acrylic amides by photocatalytic decarboxylation.Through the radical 7-endo cyclization,we synthetized a series of benzazepine derivatives which show the significant biological activities under the mild and efficient reaction condition.Then this method was also applied for efficient grafting of the benzazepine scaffold into pharmaceutically active ursolic acid skeleton.Based on control experiments,we proposed that the activation of the alkyl N-(acyloxy)phthalimide by its hydrogen bonding interaction with water is very crucial for this reaction.