Studies On The Synthesis Of Nitrogen-Containing Heterocyclic Compounds Promoted By Light

Photoredox-catalyzed organic reactions,which is an concernful branch in the field of organic synthesis,and luminous energy as a green,clean energy to promote the synthesis of organic compounds has great advantages.In addition,the synthesis of nitrogen-containing heterocyclic compounds is a key research direction in the fields of heterocyclic chemistry and medicinal chemistry.In this paper,the synthesis of nitrogen-containing heterocyclic groups under light promotion will be carried out with the theme of green organic synthesis,and the functional nitrogen heterocyclic compounds of difluoromethylated oxindoles,cyanoalkylsulfonylated oxindoles,difluoromethylated quinazolinones,and phosphonylated quinazolinones as the backbone are successfully synthesized,which provides a new research idea for photochemical synthesis methodology.The main results are as follows:（1）A visible-light-induced N-aryl acrylamide,difluoroacetic acid and（diacetoxyiodo）benzene three components radicals tandem cyclic addition synthesis method was developed,wherein difluoroacetic acid and（diacetoxyiodo）benzene can produce reagents with high optical activity during the reaction process,the difluoro hypervalent iodine reagents is photo-excited to produce difluoromethyl radicals.The reaction did not have any transition metals,additives,bases or external photosensitizers added,and the inexpensive,readily available difluoroacetic acid was used as a difluoromethylation reagent and biomass-derived solvent 2-methyltetrahydrofuran as the reaction medium,405 nm as an effective light source,the conditions were mild,the operation steps were simple,and the reaction was efficient.Due to the potential biological activity of difluoromethylated oxindoles,this synthesis method is expected to be an ideal strategy for the preparation of difluoromethylated drug molecules.（2）A visible-light-mediated cyclization of N-aryl acrylamide,cyclobutanone oxime and potassium metabisulfite involved in the series cyclization of photochemical radicals,potassium metabisulfite in the reaction can be used as a precursor of SO₂,is an effective external source of sulfonyl groups,this reaction is formed into cyanoalkyl radicals by C-C bond cleavage of cyclobutanone imine radicals,and then capture SO₂in the reaction system to generate new radicals to achieve the synthesis of the target product.A green,efficient synthesis strategy is provided for the acquisition of various cyanoalkylsulfonylated oxindoles.This method avoids the use of transition metals,photosensitizers,and stoichiometric oxidants to catalyze reactions,and is a convenient way to obtain cyanoalkylsulfonylated oxindoles.This method synthesizes a series of cyanoalkylsulfonylated oxindole molecules under mild conditions,and the synthesized compounds have cyano group,which can occur further esterification reactions with alcohols under the catalysis of concentrated sulfuric acid,expanding the scope of modification and application value.（3）Under the condition of light source wavelength of 440 nm,the use of visible light to induce the unactivated olefin-substituted quinazolinone,difluoroacetic acid and（diacetoxyiodo）benzene radicals cycloadditions,the reaction involves the generation of difluoromethyl radicals,this method provides a green and efficient synthesis route for obtaining difluoromethylated quinazolinones.In terms of substrate expandability,the fluoridation reagent can be expanded from difluoroacetic acid（CHF₂CO₂H）to difluorochloroacetic acid（CCl F₂CO₂H）and difluorobromoacetic acid（CBr F₂CO₂H）,and the introduction of bromine atoms and chlorine atoms not only expands the substrate range of the reactions,but also increases the possibility of late modification of difluoromethylated quinazolinone.（4）Under visible light conditions,tetrabromofluorescein（Eosin Y）as a photosensitizers,oxygen in the air as an oxidant to induce aryl phosphorus oxide dehydrogenation to produce phosphoryl radicals,and quinazolinones which have unactivated olefins undergo radical addition,through intramolecular cyclization synthesis of a series of phosphonylated quinazolinone molecules.According to the relevant literature,phosphonylated quinazolinones may be a candidate compound for novel pesticide molecules as well as other drug molecules.The method abandons expensive metal photosensitizers and uses the inexpensive Eosin Y as a carrier for electron transfer,the biomass derivative 2-Me THF as a green solvent,and obtains a series of phosphonylated quinazolinone compounds at room temperature with good to excellent yields.