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Advances in Free Radical Reactions of Organoselenium and Organotellurium Compounds

Craig; Walter R. Speakers included:. Download the Program for the 7th NOS 22 pages. Billings Local Organizers: V. Chambers, W. Hartman, S. Davidson, R. Helmkamp, T. Staub, G. Lux, Edwin Wiig Speakers:. Johnson Local Organizers: Melvin L. Nichols, Ralph C. Tallman, R. Conner, Harold R. Snyder, Marcus G. Van Campen, Jr.

Bryant, Milton T. Bush, L. Davy, Tom L. Jacobs Speakers:. Donleavy, Arthur J. Hill, James B. Conant, Howard J. Lucas, J. Bailey, L. Fieser, Reynold C. Fuson, G. Burns Speakers:. Symposium Executive Officer: F. Stewart Local Organizers: A most active committee from the Princeton faculty and graduate group Speakers:. In addition to the reading and discussion of the above papers, several colloquia were held.

Crossley, Chairman, Calco Chemical Co. Hill, Wesleyan University; T. Stewart, University of California. Dains, Chairman, University of Kansas; E. Conant, Harvard University. Smith, University of Minnesota. Evans Local Organizers: C. Boord, Charles D. Hurd, secretary Speakers:. December , in Rochester, N. Symposium Executive Officer: Marston T. Bogert Local Organizer: W.

Webb Speakers:. N27 on file in their Rare Books Collection. A copy of the program book is posted here pages, Home — NOS History. Baran, The Scripps Research Institute. Burke, University of Illinois, Urbana-Champaign. Carpenter, Cardiff University. David, University of California, Davis. Faul, Amgen Inc. Floreancig, University of Pittsburgh. Kozlowski, University of Pennsylvania. Moore, University of Illinois at Urbana-Champaign.

Reisman, California Institute of Technology. Wender, Stanford University. Miller, Yale University. Molander, University of Pennsylvania. Ondari, The Dow Chemical Company. Coleman, Merck Research Laboratories. Fowler, Brookhaven National Laboratory. Kelley, University of Toronto. Roush, Scripps Florida. Scott, Boston College. Sleiman, McGill University. Grubbs, California Institute of Technology. Corey, Harvard University. Denmark, University of Illinois at Urbana Champaign.

Feringa, University of Groningen. Liu, Harvard University. Sorensen, Princeton University. Stoltz, California Institute of Technology. Dean Toste, University of California, Berkeley. Trost, Stanford University. Wooley, Washington University in Saint Louis. Groves, Princeton University. Nicolaou, The Scripps Research Institute. Blackmond, University of Hull, UK. Evans, Harvard University. Kiessling, University of Wisconsin.

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Kool, Stanford University. Leighton, Columbia University. MacMillan, California Institute of Technology. Overman, University of California, Irvine. Schultz, Scripps Research Institute. Shair, Harvard University. Swager, Massachusetts Institute of Technology. Wood, Yale University. Bertozzi, University of California, Berkeley. Andrew Evans, Indiana University. Johnson, Wayne State University. Kelly, The Scripps Research Institute. Lipshutz, University of California, Santa Barbara.

Lyle Speakers: K. Meyers, Colorado State University. Seeman, Philip Morris. Clark Still, Columbia University. Tian Speakers: Barry M. Buchwald, Massachusetts Institute of Technology. Jorgensen, Yale University. Platz, Ohio State University. Roberts, California Institute of Technology. Fraser Stoddart, University of Birmingham. Myers, California Institute of Technology. Schreiber, Harvard University. Tomalia, Michigan Molecular Institute. Walsh, Harvard Medical School.

White, Oregon State University. Dykhuis Speakers: Gilbert J. Curran, University of Pittsburgh. Dervan, California Institute of Technology. Dougherty, California Institute of Technology. Eaton, University of Chicago. Houk, University of California, Los Angeles. Bergman, University of California, Berkeley. Heathcock, University of California, Berkeley. Magnus, Indiana University. Schultz, University of California, Berkeley. Whitesides, Harvard University. Gassman, University of Minnesota. Kaiser Rockefeller University.

Knowles, Harvard University. Nicolaou, University of Pennsylvania. Dale Poulter, University of Utah. Schreiber, Yale University. Smart Speakers: Donald J. Bartlett, University of California, Berkeley. Casey, University of Wisconsin. DePuy, University of Colorado at Boulder. Stille, Colorado State University. Walsh, Massachusetts Institute of Technology. Bunnett, University of California, Santa Cruz. Schuster, University of Illinois at Urbana Champaign. Barry Sharpless, Massachusetts Institute of Technology. Wiberg, Yale University. Smith Speakers: Nelson J.

Chapman, University of California, Los Angeles. Houk, University of Pittsburgh. House, Georgia Institute of Technology. Kende, University of Rochester. Paquette, The Ohio State University. Trost, University of Wisconsin. Bordwell, Northwestern University. DeLuca, University of Wisconsin. Grieco, University of Pittsburgh. Ireland, California Institute of Technology. Jerina, National Institutes of Health. Uskokovic, Hoffmann-La Roche. Peter C. Vollhardt, University of California, Berkeley.

Winston Speakers: William S. Brauman, Stanford University. Cram, University of California, Los Angeles. Evans, California Institute of Technology. Semmelhack, Cornell University. Woodward, Harvard University. Bard, University of Texas, Austin. Subsequent lower O 2 diffusion to mitochondria during energy synthesis increases more generation of free radicals and acids in possible continuing vicious cycles toward creating or maintaining most pathology known to mankind.

Free radicals are also associated with crosslinking proteins and collagen to stiffen the extracellular matrix in much pathology. Most importantly, hydroquinone, a free-radical inhibitor designed to efficiently sequester free radicals, is a potential pharmaceutical for medical treatment. National Center for Biotechnology Information , U. Author manuscript; available in PMC Jul 6. Author information Copyright and License information Disclaimer. Copyright notice. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Unsaturated carbon-carbon double bonds particularly at exposed end groups of nonsolid fluids are susceptible to free-radical covalent bonding on one carbon atom creating a new free radical on the opposite carbon atom. Keywords: Free radical, Molecular oxygen, Reactive oxygen species, Reactive secondary sequence, Polymerization, Lipid peroxidation, Membrane fluidity, Free-radical inhibitor. Open in a separate window.

Figure 1. Figure 2. Figure 3. Cell Membranes Free radicals can result in reducing membrane fluidity to increase membrane rigidity [ 2 , 9 , 46 — 50 ]. Cancer As presented previously, elevated pathologic ROS levels and oxidative damage can decrease membrane fluidity [ 2 , 9 , 46 — 50 ]. Figure 4. Figure 5. Figure 6. Figure 7. Diabetes ROS are involved in the development of obesity or diabetes and further thought to promote insulin resistance [ ].

Infection and Inflammation Responses Infection or tissue damage can elicit an inflammatory response [ — ]. Free-Radical Theory for Ageing Regarding Vitamins as Antioxidants and Clinical Error The Free-Radical Theory of Ageing asserts that ageing is due to the accumulation of free-radical biologic damage which increases disease and death [ 19 , 20 ]. Free-Radical Inhibitor Hydroquinone Important antioxidant properties of fruits and vegetables may be derived from compounds other than vitamins not yet known [ , ].

Figure 8. Molecular structures for vitamin E top compared to hydroquinone bottom. Figure 9. Conclusions Free radicals generated under mitochondrial oxidative stress are associated with excess production of electrons and acid. References 1.

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Petersen RC. Reactive secondary sequence oxidative pathology polymer model and antioxidant tests. Free radicals and advanced chemistries involved in cell membrane organization influence oxygen diffusion and pathology treatment. AIMS Biophysics. Free-radical polymer science structural cancer model: A review. Subject Area: Molecular Biology. Article ID Zumdahl SS. McMurry J. Organic Chemistry. Chapter X. Advances in Experimental Medicine and Biology. Srinivasan S, Avadhani N. Cytochrome c oxidase dysfunction in oxidative stress. Free Radical Biology and Medicine. Oxidative damage and mitochondrial decay in aging.

Mitochondria, oxidants, and aging. Zimniak P. Relationship of electrophilic stress to aging. Finkel T, Holbrook N. Oxidants, oxidative stress and the biology of ageing. Serial review: the powerhouse takes control of the cell: the role of mitochondria in signal transduction. The aging process and potential interventions to extend life expectancy. Clinical Interventions in Aging. Murphy M. How mitochondria produce reactive oxygen species. Biochemical Journal. Mitochondrial targeting of electron scavenging antioxidants: regulation of selective oxidation vs random chain reactions.

Advanced Drug Delivery Reviews. Schieber M, Chandel N. ROS function in redox signaling and oxidative stress. Current Biology. Harvery R, Ferrier D. Chapter 3 Globular Proteins; p. Harman D. Aging: a theory based on free radical and radiation chemistry. Journal of Gerontology. Free radical theory of aging: an update. Annals of the New York Academy of Sciences. Free radicals in the physiological control of cell function. Physiological Reviews.

Free radicals and antioxidants in normal physiological functions and human disease. Girotti A. Lipid hydroperoxide generation, turnover, and effector action in biological systems. Journal of Lipid Research. Beckman K, Ames B. The free radical theory of aging matures. Free radicals, metals and antioxidants in oxidative stress-induced cancer. Chemico-Biological Interactions. Silva J, Coutinho O. Free radicals in the regulation of damage and cell death-basic mechanisms and prevention. Markers of oxidant stress that are clinically relevant in aging and age-related disease.

Mechanisms Ageing and Development. Free radicals: properties, sources, targets, and their implication in various diseases. Indian Journal of Clinical Biochemistry. Mitochondrial and apoptotic neuronal death signaling pathways in cerebral ischemia. Oxidative Medicine and Cellular Longevity.

Article ID [ Google Scholar ]. Translational research involving oxidative stress diseases of aging. Sena L, Chandel N. Physiological roles of mitochondrial reactive oxygen species. Molecular Cell. Labunskyy V, Gladyschev V. Role of reactive oxygen species-mediated signaling in aging. Hill S, Remmen H. Mitochondrial stress signaling in longevity: a new role for mitochondrial function in aging.

Redox Biology. Stocker R, Keaney JF. Role of oxidative modifications in atherosclerosis. Chapter 27 Biomolecules: Lipids; pp. Sherwood L. Human Physiology. Lipids; pp. Tensional homeostasis and the malignant phenotype. Cancer Cell. Collagen reorganization at the tumor-stromal interface facilitates local invasion.

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Validation of lysyl oxidase as a prognostic marker for metastasis and survival in head and neck squamous cell carcinoma: Radiation therapy oncology group trial 90— Journal of Clinical Oncology. Matrix crosslinking forces tumor progression by enhancing integrin signaling. Nature Medicine. Tumor mechanics and metabolic dysfunction. Microsomal lipid peroxidation causes an increase in the order of the membrane lipid domain. FEBS Letters.

Iron-induced lipid peroxidation and protein modification in endoplasmic reticulum membranes. Protection by stobadine. Abnormalities of erythrocyte membrane fluidity, lipid composition, and lipid peroxidation in systemic sclerosis. Smoking and fluidity of erythrocyte membranes: a high resolution scanning electron and atomic force microscopy investigation.

Nitric Oxide. Effect of oxidative stress on plasma membrane fluidity of THP-1 induced macrophages. Chapter New York: Garland Science; Membrane Structure. The Lipid Bilayer. Weijers R. Lipid composition of cell membranes and its relevance in type 2 diabetes mellitus. Current Diabetes Reviews. The cell membrane as a biosensor of oxidative stress induced by radiation exposure: a multiparameter investigation.

Radiation Research. Diffusion and rheology of binary polymer mixtures. Singer S, Nicolson G. The fluid mosaic model of the structure of cell membranes. Nicolson G. The fluid-mosaic model of membrane structure: still relevant to understanding the structure, function and dynamics of biological membranes after more than 40 years. Dietary fat: exogenous determination of membrane structure and cell function.

Chemical modifications in aggregates of recombinant human insulin induced by metal-catalyzed oxidation: covalent crosslinking via Michael addition to tyrosine oxidation products. Pharmaceutical Research. The impact of specific oxidized amino acids on protein turnover in J cells. NADPH oxidase 4 deficiency leads to impaired wound repair and reduced dityrosine-crosslinking, but does not affect myofibroblast formation. Inactivation of SMN complex by oxidative stress. Inactivation of human DGAT2 by oxidative stress on cysteine residues.

Kang JH. Modification and inactivation of CU, Zn-superoxide dismutase by the lipid peroxidation product, acrolein. BMB Reports. A low degree of fatty acid unsaturation leads to lower lipid peroxidation and lipoxidation-derived protein modification in heart mitochondria of the longevous pigeon than in the short-lived rat.

Mechanisms of Ageing and Development. Membrane fluidity and oxygen diffusion in cholesterol enriched erythrocyte membrane. Archives of Biochemistry and Biophysics. Decreased membrane fluidity and altered susceptibility to peroxidation and lipid composition in overweight and obese female erythrocytes. Membrane fluidity and oxygen diffusion in cholesterol-enriched endothelial cells. Clinical Hemorheology and Microcirculation.

On respiratory impairment in cancer cells. Gillies R. Novartis Foundation Symposium. Stavridis J. Oxidation: the Cornerstone of Carcinogenesis. New York: Springer; Grek C, Tew K. Redox metabolism and malignancy. Current Opinion in Pharmacology. Mitochondria in cancer: at the crossroads of life and death. Chinese Journal of Cancer. Hielscher A, Gerecht S. Hypoxia and free radicals: role in tumor progression and the use of engineering-based platforms to address these relationships. Reactive oxygen species, nutrition, hypoxia and diseases: problems solved? The interplay of reactive oxygen species, hypoxia, inflammation, and sirtuins in cancer initiation and progression.

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    A mild radical cascade reaction is based on sulfonyl radical generation from the appropriate sodium sulfinate and Eosin Y 11a under blue LED irradiation Scheme 15 a. More stable form of radical —radical undergoes subsequent addition to the double bond of generating radical , which yields radical by intramolecular cyclization. The photocatalytic cycle is completed by the reaction of Eosin hydride with proton, which leads to the release of hydrogen from the reaction mixture.

    Similar to N -containing heterocycles, their oxygen analogues can be also found in many natural products and pharmaceuticals [ 54 , 55 ], attracting broad interests by scientific community. A new route toward the synthesis of a functionalized furan ring has been recently disclosed by Lei and co-workers [ 56 ]. This highly selective method of constructing substituted furans is based on the usage of Methylene Blue 13 as catalyst in combination with NH 4 2 S 2 O 8 as a terminal oxidant. General mechanism for this transformation is disclosed in Scheme 16 b.

    Subsequent hydrogen atom transfer between and sulfate radical anion forms intermediate , which undergoes intermolecular addition to the triple bond of alkyne with the formation of radical Next, intramolecular radical addition to the carbonyl oxygen forms a five-membered O-heterocycle radical. In addition to heteroaromatic compounds, their non-aromatic oxygen-containing analogues are equally important.

    Butyrolactones are a class of heterocycles highly prevalent in nature, indicating many interesting bioactivities [ 57 , 58 ]. Given their importance, many synthetic strategies for their preparations have been elaborated, including photoredox catalysis. The photoredox reaction is carried out using the Fukuzimi acridinium 12 photooxidant, easily accessible oxime acids and alkenes Using given methodology, various lactones with high functional group variations are accessible in very good yields Scheme 17 a. Next, the radical reacts with the oxime acid resulting in the formation of the radical Subsequent deprotonation of compound , followed by intramolecular 5- exo -trig radical cyclization furnishes N -centered radical Finally, hydrogen atom transfer between and affords final product and regenerates the acridinium catalyst 12 in its ground state.

    Authors indicated, however, that another mechanistic pathway without the use of H-atom donor co-catalyst might be involved. The synthesis of structurally similar butyrolactones by metal-free visible-light-mediated catalysis has been also described by Liu [ 61 ] and Shah groups [ 62 ]. An impressive example of a chiral ion-pair photoredox organocatalyst [ 64 ] in enantioselective hydroetheryfication of alkenols in stereoselective synthesis of tetrahydrofuran analogs has been recently disclosed by Luo and co-workers [ 65 ]. The described work showed that ion pair catalysts indicate improved activity compared to Fukuzimi catalysts 12 and proves that visible-light-mediated catalysis is feasible for stereoselective transformations Scheme 18 a.

    This reaction is based on the three stage process: single electron transfer, cyclization, and hydrogen transfer and has been described already in detail by Nicewicz group [ 60 ]. Phosphate anion in ion pair catalyst endows a longer lifetime of the chiral photocatalysts triplet state, introduces chirality, and assists in the H-shift Scheme 18 b.

    Ionic approach for polyene cyclization has been extensively explored, thus constituting the main synthetic strategy of polyene ring synthesis [ 69 ]. However, stereoselective radical cyclization can also have significant benefits [ 70 ]. In this context, Zhang and Luo group [ 71 ] demonstrated visible-light-induced cyclization of polyenes in the synthesis of various oxygen-containing heterocycles Scheme 20 a. The reported protocol is based on radical cascade cyclization using Eosin Y 11a as a catalyst and green LEDs. In Scheme 20 b, a reasonable mechanism for this transformation is suggested.

    The generated radical undergoes intramolecular radical cascade cyclization together with the hydrogen shift to the intermediate In addition to the sulfonated quinolines Scheme 6 , its oxygen containing analogs—cumarines can be also obtained. In this context, various alkynes undergoe arylsulfonylation with arylsulfinic acid and TBHP using Eosin Y 11a as a catalyst. It is noteworthy that appropriate cumarines can be obtained in good yields with a wide functional group tolerance [ 72 ].

    An efficient and straightforward strategy for building functionalized, N - or O -bearing heteroatoms is the 1,3-dipolar cycloaddition [ 73 ]. Xia, Yang and collaborators [ 74 ] described visible-light-mediated anti -regioselective 1,3-dipolar cycloaddition of nitrones with alkenes Scheme 21 a.

    The nitrones are cyclized with styrenes and aliphatic alkenes via a polar radical crossover cycloaddition reaction using triphenylpyrrylium catalyst 8b under blue light irradiation. This transformation is based on the mechanism presented in Scheme 21 b. Electrophilic addition of intermediate to nitrone , followed by a radical cyclization leads to the intermediate This intermediate act as an oxidant enabling regeneration of the catalyst by electron transfer alongside with the product formation.

    The authors also suggest a possible radical chain propagation between and alkene Woo group [ 75 ] unveiled that nitrones can be also generated in situ from oxaziridines in photoredox conditions. On the basis of a series of experiments, the following mechanism is proposed by the authors Scheme 22 b. The radical cation is then converted into the nitrone radical through the ring opening process. Due to the importance of this group, Cho and co-workers developed oxidative cyclization of amidoximes under visible-light conditions [ 77 ].

    Described protocol involves the intramolecular oxidative cyclization of amidoximes in the presence of the triphenylpyrylium 8c catalyst and molecular oxygen as the oxidant, promoted by compact fluorescent lamp Scheme 23 a. Opposite to all previous examples, in this particular transformation T p -F PPT act as both an electrophilic catalyst and a photocatalyst due to the fact that reaction works also in the dark, although less efficient. The authors proposed a possible mechanism for this transformation Scheme 23 b. Reaction starts by the nucleophilic addition of to the triphenylpyrrylium ion and generates intermediate , which undergoes homolytic dissociation and produce two radicals: and Additionally, this process is accelerated by the visible-light irradiation.

    The catalyst is then regenerated by the molecular oxygen oxidation of intermediate. Beside catalyst regeneration cycle, the radical undergoes an intramolecular 1,5-hydrogen atom transfer HAT and produces the radical Subsequent oxidation of the compound to the iminium ion by molecular oxygen or excited catalyst followed by intramolecular cyclization yields the final product Many natural or synthetic compounds containing oxazoline scaffold have been found to possess some level of interesting bioactivities [ 78 ].

    Moreover, these structures are important building blocks in the syntheses of many chiral ligands in stereoselective synthesis [ 79 ]. Therefore, novel methodologies for the synthesis of these structural motifs are highly desirable. In this context, Nicewicz and co-workers disclosed photoredox-catalyzed hydrofunctionalization of unsaturated amides and thioamides in the synthesis of 2-oxazolines and 2-thiazolines [ 80 ].

    This intramolecular functionalization is based on dual catalytic system comprised from and phenyl disulphide Scheme 24 a. In Scheme 24 b, a reasonable mechanism for this transformation is suggested. Subsequent cyclization and proton loss affords cyclic radical intermediate Finally, hydrogen atom transfer from thiophenol generates product and a thiyl radical Presented procedure is based on the cleavage of an aryl trifluoromethoxy ether and in situ conversion of formed fluorophosgene for the synthesis of carbamates, carbonates, and urea derivatives Scheme 25 a.

    The reported protocol is based on the single-electron reduction of 4- trifluoromethoxy benzonitrile and its fragmentation into fluorophosgene a , which undergoes further intramolecular cyclization with 1,2-diamines, aminoalcohols or diols Scheme 25 b. In this way, carbonates, various carbamates, and urea derivatives can be prepared in moderate to excellent yields.

    Quinazolines are another class of heterocyclic compounds extensively studied.

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    Itoh et al. A possible mechanism as proposed by the authors is disclosed in Scheme 26 b. Initially, cyclization between the diamine and the aldehyde takes place leading to the diamine Subsequent energy transfer from triplet RB catalyst to oxygen produces reactive singlet oxygen 1 O 2 responsible for the oxidation of the compound into the final product More recently, Das group also demonstrated cyclization of the diamines and aldehydes into heterocycles , but in different reaction conditions [ 83 ] Scheme In this context, a corresponding amine formed upon cyclization of diamine and aldehyde is dehydrogenated and aromatized to the product Tang group demonstrated that the given methodology tolerates a wide range of functional groups with a higher reaction efficiency [ 84 ].

    The cyano moiety is widely used in organic synthesis because it undergoes many important transformations [ 85 ]. Sun et al. This visible-light-induced cascade reaction is initiated by the intermolecular radical addition of alkyl carbazate to a double bond of N -arylacrylamide followed by cyano-mediated cyclization. The suggested mechanism is depicted in Scheme 28 b. Sequential dehydrogenation of followed by nitrogen release provides alkoxycarbonyl radical At this moment, generated radical reacts with double bond of the starting material leading to the intermediate , which undergoes intramolecular cyclization with cyano group to the radical intermediate path a.

    Alternatively, the radical can undergo intramolecular cyclization with the aromatic ring path b leading to the undesired product in trace amount. Final product is obtained by the deprotonation of intermediate On the basis of a series of control experiments, the authors proposed a plausible catalytic cycle Scheme 29 b. Quinazolinone structure is another important structural unit in heterocyclic chemistry [ 1 , 2 , 3 ]. Idrolone, Hydromox, and sildenafil citrate are the representative drugs containing quinazolinone motif.

    Presented strategy features mild reaction conditions and broad substrate suitability. On the basis of their experimental observations and literature studies, authors proposed the mechanism depicted in Scheme 30 b. Subsequent hydrogen atom removal from produces sulfur-centered radical , which undergoes addition to the double bond of and produces radical intermediate Finally, deprotonation of gives the expected product In addition to the given examples, other heterocycles containing multiple heteroatoms like imidazopyridines [ 89 ] or oxadiazoles [ 90 ] can be also obtained using metal-free visible-light-mediated catalysis.

    In this review, recent advances in the synthesis of nitrogen and oxygen heterocyclic compounds via a metal-free visible-light-induced catalysis have been discussed. It has been shown that various metal-free organic dyes are effective photo-redox catalysts in the synthesis of many structurally different heterocycles containing one or more heteroatoms. Both non-aromatic and aromatic heterocyclic units are readily accessible by using visible-light-mediated catalysis in a straightforward modular way. Reported works indicate that organic dyes capable of visible-light-spectra absorption act as an attractive alternative to the transition-metal complexes.

    The variety of the presented examples indicates the potential use of the described methodologies in organic synthesis, drug discovery, or materials science. Moreover, the use of inexpensive organic, transition metal-free catalysts makes described protocols very practical and hold promise for broader application in industry and scientific community.

    Synthesis of 3- trifluoromethyl indolinone derivatives under photoredox conditions. Conceptualization, M. Sample Availability: Samples of the compounds are not available from the authors. Europe PMC requires Javascript to function effectively. Recent Activity. The snippet could not be located in the article text.

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    This may be because the snippet appears in a figure legend, contains special characters or spans different sections of the article. Published online Apr PMID: Gianfranco Favi, Academic Editor. Received Mar 27; Accepted Apr Abstract Heterocycles are important class of structures, which occupy a major space in the domain of natural and bioactive compounds.

    Keywords: photocatalysis, photoredox, visible-light-induced catalysis, photoredox cyclization, organic dyes, heterocycles. Introduction Heterocycles are a very important class of structural motifs that can be found in many pharmaceuticals and natural products [ 1 , 2 , 3 ]. Open in a separate window. Figure 1. Selected example of current drugs containing heterocyclic scaffold. Figure 2. Application of Visible-Light-Mediated Catalysis in Synthesis of Heterocyclic Compounds Many organic compounds isolated from nature contain five- or six-membered heterocycle scaffolds.

    N-containing Heterocycles 2. Aromatic Heterocycles Nitrogen bearing heterocycles constitute the majority in the field of heterocyclic chemistry. O-Containing Heterocycles 2. Aromatic Heterocycles Similar to N -containing heterocycles, their oxygen analogues can be also found in many natural products and pharmaceuticals [ 54 , 55 ], attracting broad interests by scientific community.

    Non-Aromatic Heterocycles In addition to heteroaromatic compounds, their non-aromatic oxygen-containing analogues are equally important. Heterocycles Bearing More Than One Heteroatom An efficient and straightforward strategy for building functionalized, N - or O -bearing heteroatoms is the 1,3-dipolar cycloaddition [ 73 ]. Conclusions In this review, recent advances in the synthesis of nitrogen and oxygen heterocyclic compounds via a metal-free visible-light-induced catalysis have been discussed.

    Scheme 1. Scheme 2. Scheme 3. Dehydrogenative cascade trifluoromethylation and oxidation of 1,6-enynes. Scheme 4. Scheme 5.