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Articoli di riviste sul tema "Photo-cyclization"

Autore: Grafiati

Pubblicato: 2 novembre 2024

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1

Zhao, Lishuang, Hongyue Zhang, Jianing Cui, Meiqi Zhao, Zhiqiang Wang, Qunfeng Yue e Yingxue Jin. "Photo-induced synthesis and in vitro antitumor activity of Fenestin A analogs". New Journal of Chemistry 41, n. 23 (2017): 14044–48. http://dx.doi.org/10.1039/c7nj03363j.

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2

Yao, Zhuojun, Xueting Wu, Xiaocui Zhang, Qin Xiong, Shichao Jiang e Zhipeng Yu. "Synthesis and evaluation of photo-activatable β-diarylsydnone-l-alanines for fluorogenic photo-click cyclization of peptides". Organic & Biomolecular Chemistry 17, n. 28 (2019): 6777–81. http://dx.doi.org/10.1039/c9ob00898e.

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3

Rajeshkumar, Venkatachalam, e Mihaiela C. Stuparu. "A photochemical approach to aromatic extension of the corannulene nucleus". Chemical Communications 52, n. 64 (2016): 9957–60. http://dx.doi.org/10.1039/c6cc04910a.

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4

Connor, Dennis A., Donald R. Arnold, Pradip K. Bakshi e T. Stanley Cameron. "Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 9: methanol-2,6-dimethyl-1,6-heptadiene, and 1,4-dicyanobenzene". Canadian Journal of Chemistry 73, n. 6 (1 giugno 1995): 762–71. http://dx.doi.org/10.1139/v95-096.

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Abstract (sommario):

The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction of methanol, 2,6-dimethyl-1,6-heptadiene, and 1,4-dicyanobenzene yields three distinct types of 1:1:1 adducts: an acyclic product, 4-(1-methoxymethyl-1,5-dimethyl-5-hexenyl)benzonitrile (8, 5%); a cis–trans pair of cyclohexanes, 4-(3-methoxymethyl-1,3-dimethylcyclohexyl)benzonitrile (9cis (12%) and 9trans (11%)); and a cis–trans pair of cycloheptanes, 4-(4-methoxy-1,4-dimethylcycloheptyl)benzonitrile (10cis (12%) and 10trans (10%)). Variation in the concentration of the nucleophile, methanol, and codonor, biphenyl, affects the product ratio and it has been possible to establish the mechanisms for the formation of these products. The acyclic product is formed by a typical photo-NOCAS reaction, that is, addition (anti-Markovnikov) across one of the heptadiene double bonds. The cyclohexane products are formed following 1,6-endo cyclization of the intermediate β-alkoxy radical. And the cycloheptane products result from 1,7-endo,endo cyclization of the initially formed 2,6-dimethyl-1,6-heptadiene radical cation. Comparison of the relative rates of these cyclization processes can be made with those of the next smaller homolog, 2,5-dimethyl-1,5-hexadiene. Keywords: photochemistry, photoinduced electron transfer, radical ions, radicals, cyclization.

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5

Chen, Ling, Yu-Ming Cui, Zheng Xu, Jian Cao, Zhan-Jiang Zheng e Li-Wen Xu. "An efficient approach toward formation of polycyclic coumarin derivatives via carbocation-initiated [4+2] cycloaddition and atom-economical photo-irradiated cyclization". Chemical Communications 52, n. 74 (2016): 11131–34. http://dx.doi.org/10.1039/c6cc05698a.

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Polycyclic coumarin derivatives were easily prepared by carbocation initiated [4+2] cycloaddition of propargyl silyl ethers with ynamides and fluorescent analysis-oriented photo-irradiated cyclization.

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6

Kim, Kyung-su, You Kyoung Chung, Hyunwoo Kim, Chae Yeon Ha, Joonsuk Huh e Changsik Song. "Additive-free photo-mediated oxidative cyclization of pyridinium acylhydrazones to 1,3,4-oxadiazoles: solid-state conversion in a microporous organic polymer and supramolecular energy-level engineering". RSC Advances 11, n. 4 (2021): 1969–75. http://dx.doi.org/10.1039/d0ra09581h.

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7

Mizutsu, Ryo, Ryosuke Asato, Colin J. Martin, Mihoko Yamada, Yoshiko Nishikawa, Shohei Katao, Miku Yamada, Takuya Nakashima e Tsuyoshi Kawai. "Photo-Lewis Acid Generator Based on Radical-Free 6π Photo-Cyclization Reaction". Journal of the American Chemical Society 141, n. 51 (8 dicembre 2019): 20043–47. http://dx.doi.org/10.1021/jacs.9b11821.

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8

Arnold, Donald R., Kimberly A. McManus e Xinyao Du. "Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6: methanol, nonconjugated dienes, and 1,4-dicyanobenzene". Canadian Journal of Chemistry 72, n. 2 (1 febbraio 1994): 415–29. http://dx.doi.org/10.1139/v94-063.

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Irradiation, through Pyrex, of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1) and 1,5-hexadiene (9) leads to formation of ortho and meta cyclic adducts (13–16) arising from the intermediate exciplex. There was no evidence for interaction between the two double bonds of this nonconjugated diene. The oxidation potential of 9 is high enough (> 3 V vs. sce) to preclude single electron transfer (SET); no photo-NOCAS products are formed. Similar irradiation of acetonitrile–methanol solutions of 1 and 2-methyl-1,5-hexadiene (10) does yield a photo-NOCAS product (17); reaction occurs only on the more heavily substituted double bond. The additional substitution on the double bond lowers the oxidation potential (2.70 V vs. sce) of this diene to the point where SET from 10 to the excited singlet state of 1 can occur. In this case, no cycloaddition products are formed; the exciplex is quenched by electron transfer. There was no evidence for interaction between the two double bonds of the initially formed radical cation 10+•, or between the terminal double bond and the β-alkoxyalkyl radical of the intermediate leading to the photo-NOCAS product. The photo-NOCAS product (19) was also formed when 2,5-dimethyl-1,5-hexadiene (11) was subjected to these reaction conditions. In this case, when biphenyl (4) was added as a codonor, in addition to the photo-NOCAS product, products (21cis and trans) resulting from cyclization of the initially formed acyclic radical cation 11+• to give the 1,4-dimethylcyclohexane-1,4-diyl radical cation were also observed. This 1,6-endo, endo cyclization of 11+• must be rapid enough to compete with reaction with methanol. There was no evidence for cyclization (neither 1,4-exo nor 1,5-endo) of the intermediate β-alkoxyalkyl radical. When the radical cation of 2,5-dimethyl-1,4-hexadiene (12+•) is generated under these reaction conditions, photo-NOCAS products 22 and 23 are formed at the more heavily substituted double bond, along with the conjugated tautomer 2,5-dimethyl-2,4-hexadiene (24). The mechanisms for these transformations are discussed.

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9

Zhou, Zhao-Zhao, Jia-Hui Zhao, Xue-Ya Gou, Xi-Meng Chen e Yong-Min Liang. "Visible-light-mediated hydrodehalogenation and Br/D exchange of inactivated aryl and alkyl halides with a palladium complex". Organic Chemistry Frontiers 6, n. 10 (2019): 1649–54. http://dx.doi.org/10.1039/c9qo00240e.

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Photo-induced radical reductive dehalogenation of inactivated aryl/alkyl bromides and chlorides with a palladium complex is described. Reductive cyclization, dehalogenative deuteration, and radical addition process can be achieved smoothly.

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10

Sun, Bin, Rongcheng Shi, Kesheng Zhang, Xiaoli Tang, Xiayue Shi, Jiayun Xu, Jin Yang e Can Jin. "Photoinduced homolytic decarboxylative acylation/cyclization of unactivated alkenes with α-keto acid under external oxidant and photocatalyst free conditions: access to quinazolinone derivatives". Chemical Communications 57, n. 49 (2021): 6050–53. http://dx.doi.org/10.1039/d1cc02415a.

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A green and efficient strategy for the synthesis of quinazolinone derivatives via photo-induced decarboxylative cascade radical acylation/cyclization of unactivated alkenes has been developed under oxidant and photocatalyst free conditions.

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11

Abou-Elzahab, Μ. Μ., S. Ν. Ayyad e Μ. T. Zimaity. "Ring Expansion of Carbocyclic β-Keto-ester with Acetylenic Esters". Zeitschrift für Naturforschung B 41, n. 3 (1 marzo 1986): 363–66. http://dx.doi.org/10.1515/znb-1986-0312.

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The β-keto-ester 1b and 7 reacted with dimethyl acetylenedicarboxylate (DMAD) to give the cyclooctadienone derivatives (2a and 3b). the acid hydrolysis of which afforded the anhydride 4. Also 1a, b reacted with ethyl propiolate and gave substituted cyclooctadienone (6a, b). Michael reaction of 11 with DMAD gave adduct 12 which underwent cyclization via photo-cycloaddition (2+2) to give the photo-product (14).

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12

An, Yuanyuan, Yunyan Kuang e Jie Wu. "Synthesis of trifluoromethylated 3,4-dihydroquinolin-2(1H)-ones via a photo-induced radical cyclization of benzene-tethered 1,7-enynes with Togni reagent". Organic Chemistry Frontiers 3, n. 8 (2016): 994–98. http://dx.doi.org/10.1039/c6qo00267f.

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A photoinduced radical cyclization of benzene-tethered 1,7-enynes with Togni reagent in the presence of sodium iodide is developed. This transformation works well without any metals or photo-redox catalysts at room temperature.

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13

Wei, Wen-hao, Takenori Tomohiro, Masato Kodaka e Hiroaki Okuno. "Photo-regulated cyclization reactions of tetraazamacrocycles with azobenzene derivatives †". Journal of the Chemical Society, Perkin Transactions 1, n. 23 (1999): 3397–98. http://dx.doi.org/10.1039/a907030c.

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14

Fouad, Farid S., Curtis F. Crasto, Yiqing Lin e Graham B. Jones. "Photoactivated enediynes: targeted chimeras which undergo photo-Bergman cyclization". Tetrahedron Letters 45, n. 41 (ottobre 2004): 7753–56. http://dx.doi.org/10.1016/j.tetlet.2004.08.130.

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15

Liu, Zhong-Li, Wei Yu, Qiang Liu, Bing Han, Wei Zhang e Li Yang. "Photo-Induced Radical Cyclization of Aromatic Halides with Sodium Borohydride". Synlett, n. 14 (2005): 2248–50. http://dx.doi.org/10.1055/s-2005-872243.

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16

Evenzahav, Ariella, e Nicholas J. Turro. "Photochemical Rearrangement of Enediynes: Is a “Photo-Bergman” Cyclization a Possibility?" Journal of the American Chemical Society 120, n. 8 (marzo 1998): 1835–41. http://dx.doi.org/10.1021/ja9722943.

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17

Wei, Wen-hao, Takenori Tomohiro, Masato Kodaka e Hiroaki Okuno. "ChemInform Abstract: Photo-Regulated Cyclization Reactions of Tetraazamacrocycles with Azobenzene Derivatives." ChemInform 31, n. 19 (8 giugno 2010): no. http://dx.doi.org/10.1002/chin.200019141.

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18

Buchner, Magnus R., Bernhard Wahl e Klaus Ruhland. "Intramolecular photo-cyclization and consecutive rearrangement reactions of diazo-functionalized olefin-esters". Journal of Photochemistry and Photobiology A: Chemistry 252 (gennaio 2013): 183–93. http://dx.doi.org/10.1016/j.jphotochem.2012.12.005.

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19

Yamaguchi, Eiji, Yusuke Sudo, Norihiro Tada e Akichika Itoh. "Rare Metal-Free Photo-Aerobic Intramolecular Dehydrogenative Cyclization Reaction towards Polycyclic Heteroarenes". Advanced Synthesis & Catalysis 358, n. 20 (12 settembre 2016): 3191–95. http://dx.doi.org/10.1002/adsc.201600291.

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20

Oremus, Vladimír, Lubor Fišera, Hans-Joachim Timpe e Ute Lammel. "An unusually selective photo-induced rearrangement of 4-alkoxycarbonyl-5-formyl-2,3-dihydro-6H-1,3-oxazines. A new route to preparation of condensed lactones". Collection of Czechoslovak Chemical Communications 53, n. 12 (1988): 3171–78. http://dx.doi.org/10.1135/cccc19883171.

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Abstract (sommario):

3-R-Alkoxycarbonyl-5-formyl-2,3-dihydro-6H-1,3-oxazines IIa-IIc (R = methyl, ethyl, isopropyl) as primary photoproducts formed by a rearrangement of 3-R-alkoxycarbonyl-3a,4,6,6a-tetrahydrofuro[3,4-d]isoxazoles Ia-Ic undergo cyclization to bicyclic lactones IIIa-IIIc due to further irradiation. The photochemical transformation of compounds II into III constitutes a new kind of photo-induced rearrangement. The quantum yields are very little dependent on the presence of oxygen and polarity of the solvent. The proposed concerted mechanism of the photorearrangement is discussed.

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21

Yang, Qian, Rui Wang, Jie Han, Chenchen Li, Tao Wang, Yong Liang e Zunting Zhang. "Photo-induced tandem cyclization of 3-iodoflavones with electron rich five-membered heteroarenes". RSC Advances 7, n. 68 (2017): 43206–11. http://dx.doi.org/10.1039/c7ra07793a.

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Vinyl radicals were generated from 3-iodoflavones and occurred tandem cyclizations to synthesis a broad variety of novel polycyclic xanthone frameworks in good yields under mild and environmentally reaction conditions.

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22

Leitich, Johannes, Ingeborg Heise, Stephan Werner, Carl Krürger e Kurt Schaffner. "The photo-Nazarov cyclization of 1-cyclohexenyl phenyl ketone revisited. Observation of intermediates". Journal of Photochemistry and Photobiology A: Chemistry 57, n. 1-3 (aprile 1991): 127–51. http://dx.doi.org/10.1016/1010-6030(91)85011-5.

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23

Zhu, Benchuan, Guannan Qian, Yuli Xiao, Sheng Deng, Meng Wang e Aiguo Hu. "A convergence of photo-bergman cyclization and intramolecular chain collapse towards polymeric nanoparticles". Journal of Polymer Science Part A: Polymer Chemistry 49, n. 24 (6 ottobre 2011): 5330–38. http://dx.doi.org/10.1002/pola.25013.

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24

Arnold, Donald R., Dennis A. Connor, Kimberly A. McManus, Pradip K. Bakshi e T. Stanley Cameron. "The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 11: Involving (R)-(+)-α-terpineol and (R)-(+)-limonene, substituting on 1,4-dicyanobenzene". Canadian Journal of Chemistry 74, n. 4 (1 aprile 1996): 602–12. http://dx.doi.org/10.1139/v96-064.

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Irradiation of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1), biphenyl (5), and (R)-(+)-limonene (21) leads to formation of the 1:1:1 (methanol:21:1) photo-NOCAS adducts: 4-[(1R,2S,4R)-4-isopropenyl-2-methoxy-1-methylcyclohexyl]benzonitrile (23, 30%), 4-[(1S,2R,4R)-4-isopropenyl-2-methoxy-1-methylcyclohexyl]benzonitrile (24, 2%), 4-[(1R,2R,5R)-5-isopropenyl-2-methoxy-2-methylcyclohexyl]benzonitrile (25, 3%), and 4-[(1S,2S,5R)-5-isopropenyl-2-methoxy-2-methylcyclohexyl]benzonitrile (26, 1%). When an acetonitrile solution (no added methanol) of 1,4-dicyanobenzene (1), biphenyl (5), and (R)-(+)-α-terpineol (22) was irradiated under these conditions, the products were the cyclized 1:1 (22:1) photo-NOCAS adducts: (1R,2S,5R)-2-(4-cyanophenyl)-2,6,6-trimethyl-7-oxabicyclo[3.2.1]octane (27,21%) and (1S,4R,6R)-6-(4-cyanophenyl)-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane (28, 2%). Structural assignments were based primarily upon detailed analysis of 1H and 13C nmr spectra and, for four of the products (24, 26, 27, and 28), structures were firmly established by X-ray crystallography. The mechanism for the formation of these products is discussed, with emphasis on the intramolecular reactions of the intermediate alkene radical cations. Molecular mechanics (MM3) calculations gave information regarding the structure and energy of the conformers of 21 and 22 that was useful for predicting/explaining the observed reactivity on the basis of approach vector analysis; the transition state for cyclization incorporates the nucleophile and the alkene radical cation carbon atoms at the vertices of an obtuse triangle orthogonal to the plane of the π-system. Key words: photoinduced electron transfer, radical cations, cyclization, terpenes.

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25

Böcker, Jana K., Wolfgang Dörner e Henning D. Mootz. "Rational design of an improved photo-activatable intein for the production of head-to-tail cyclized peptides". Biological Chemistry 400, n. 3 (25 febbraio 2019): 417–27. http://dx.doi.org/10.1515/hsz-2018-0367.

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Abstract Head-to-tail cyclization of genetically encoded peptides and proteins can be achieved with the split intein circular ligation of peptides and proteins (SICLOPPS) method by inserting the desired polypeptide between the C- and N-terminal fragments of a split intein. To prevent the intramolecular protein splicing reaction from spontaneously occurring upon folding of the intein domain, we have previously rendered this process light-dependent in a photo-controllable variant of the M86 intein, using genetically encoded ortho-nitrobenzyltyrosine at a structurally important position. Here, we report improvements on this photo-intein with regard to expression yields and rate of cyclic peptide formation. The temporally defined photo-activation of the purified stable intein precursor enabled a kinetic analysis that identified the final resolution of the branched intermediate as the rate-determining individual reaction of the three steps catalyzed by the intein. With this knowledge, we prepared an R143H mutant with a block F histidine residue. This histidine is conserved in most inteins and helps catalyze the third step of succinimide formation. The engineered intein formed the cyclic peptide product up to 3-fold faster within the first 15 min after irradiation, underlining the potential of protein splicing pathway engineering. The broader utility of the intein was also shown by formation of the 14-mer sunflower trypsin inhibitor 1.

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26

Hasegawa, Eietsu, Kazuma Mori, Shiori Tsuji, Kazuki Nemoto, Taku Ohta e Hajime Iwamoto. "Visible Light-Promoted Metal-Free Reduction of Organohalides by 2-Naphthyl or 2-Hydroxynaphthyl-Substituted 1,3-Dimethylbenzimidazolines". Australian Journal of Chemistry 68, n. 11 (2015): 1648. http://dx.doi.org/10.1071/ch15396.

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The visible light-promoted reduction reactions of some organohalides were investigated using 2-aryl-1,3-dimethylbenzimidazolines (Ar-DMBIH) possessing 2-naphthyl or 2-hydroxynaphthyl substituents. In these reduction reactions, single-electron transfer from photo-excited Ar-DMBIH, attained by Xe lamp irradiation through an appropriate glass-filter (λ > 390 nm), to the halide substrates leads to the carbon–halogen bond cleavage, followed by the rearrangements of the formed carbon radicals such as 5-exo hexenyl cyclization and the Dowd–Beckwith ring expansion. Addition of 1,8-diazabicyclo[5.4.0]undec-7-ene was found to enhance the reducing ability of hydroxynaphthyl-substituted DMBIH. A household white light-emitting diode was also used as a light source for these reactions.

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27

Arnold, Donald R., e Kimberly A. McManus. "Photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction: methanol, beta-myrcene, and 1,4-dicyanobenzene. Intramolecular cyclization of an ene-diene radical cation". Canadian Journal of Chemistry 76, n. 9 (1 settembre 1998): 1238–48. http://dx.doi.org/10.1139/v98-156.

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The photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction of methanol, 7-methyl-3-methylene-1,6-octadiene ( β-myrcene, 1), and 1,4-dicyanobenzene yields five 1:1:1 adducts:cis-2-(4-cyanophenyl)-4-(1-methoxy-1-methylethyl)-1-methylenecyclohexane (15), trans-2-(4-cyanophenyl)-4-(1-methoxy-1-methylethyl)-1-methylenecyclohexane (16), 1-(4-cyanophenylmethyl)-4-(1-methoxy-1-methylethyl)cyclohexene (17), 4-[4-methoxy-3,3-dimethylcyclohex-(E)-1-ylidenyl]methylbenzonitrile (18), and 4-(1-vinyl-4-trans-methoxy-3,3-dimethylcyclohexyl)benzonitrile (19). All of these adducts are cyclic; variation in the product ratio as a function of methanol concentration indicates cyclization is occurring, 1,6-endo, with both the initially formed radical cation and with the intermediate β-alkoxyalkyl radicals. Evidence based upon comparison of the ionization and oxidation potential of β-myrcene with model alkenes and with conjugated dienes indicates the initial electron transfer involves the trisubstituted mono alkene moiety; the diene moiety, mono-substituted at a nodal position, has a higher oxidation potential. High-level ab initio molecular orbital calculations (MP2/6-31G*//HF/6-31G*) provide useful information regarding the nature (relative energies and charge and spin distribution) of the intermediate radical cations, which supports the proposed reaction mechanism. Key words: photoinduced electron transfer, radicals, radical cations, β-myrcene, cyclization.

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28

McManus, Kimberly A., e Donald R. Arnold. "The photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 10: intramolecular reactions involving alk-4-enols and 1,4-dicyanobenzene". Canadian Journal of Chemistry 73, n. 12 (1 dicembre 1995): 2158–69. http://dx.doi.org/10.1139/v95-268.

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Our study of the photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction has been extended to include alk-4-enols. Irradiation of acetonitrile solutions of the alk-4-enols, 6-methyl-5-hepten-2-ol (16) and 5-methyl-5-hexen-2-ol (17), and the aromatic, 1,4-dicyanobenzene (1), leads to cyclized 1:1 (alk-4-enol:aromatic) adducts. The addition of biphenyl (5) to the irradiation mixture, serving as a codonor, increases the yields and the efficiency of formation of the adducts. The structures assigned to the products trans-2-(isopropyl 4-cyanophenyl)-5-methyltetrahydrofuran (18, 29%) and cis-2-(isopropyl 4-cyanophenyl)-5-methyltetrahydrofuran (19, 24%) from 16 (reaction [5]), and r-2-(methyl 4-cyanophenyl)-2,t-5-dimethyltetrahydrofuran (20, 13%), r-2-(methyl 4-cyanophenyl)-2,c-5-dimethyltetrahydrofuran (21, 7%), r-3-(4-cyanophenyl)-3,t-6-dimethyltetrahydropyran (22, 11%), and r-3-(4-cyanophenyl)-3,c-6-dimethyltetrahydropyran (23, 2%), from 17 (reaction [6]), rests mainly upon analysis of the 1H and 13C nuclear magnetic resonance spectra. The structures of 19, 22, and 23 were firmly established by X-ray crystallography. The observed ratio of regioisomers indicates a strong preference for 1,5-exo-trig, relative to 1,6-endo-trig, cyclization of the intermediate alk-4-enol radical cation. The mechanistic implication of these results is discussed. Keywords: photoinduced electron transfer, radical ions, cyclization of radical cations, intramolecular reactions of radical cations.

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29

Mattioli, Roberto, Daniel Di Risola, Rodolfo Federico, Alessia Ciogli, Francesco Gasparrini, Claudio Villani, Mario Fontana et al. "Effect of Natural Deep Eutectic Solvents on trans-Resveratrol Photo-Chemical Induced Isomerization and 2,4,6-Trihydroxyphenanthrene Electro-Cyclic Formation". Molecules 27, n. 7 (6 aprile 2022): 2348. http://dx.doi.org/10.3390/molecules27072348.

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trans-Resveratrol is a natural bioactive compound with well-recognized health promoting effects. When exposed to UV light, this compound can undergo a photochemically induced trans/cis isomerization and a 6π electrochemical cyclization with the subsequent formation of 2,4,6-trihydroxyphenanthrene (THP). THP is a potentially harmful compound which can exert genotoxic effects. In this work we improved the chromatographic separation and determination of the two resveratrol isomers and of THP by using a non-commercial pentafluorophenyl stationary phase. We assessed the effect of natural deep eutectic solvents (NaDES) as possible photo-protective agents by evaluating cis-resveratrol isomer and THP formation under different UV-light exposure conditions with the aim of enhancing resveratrol photostability and inhibiting THP production. Our results demonstrate a marked photoprotective effect exerted by glycerol-containing NaDES, and in particular by proline/glycerol NaDES, which exerts a strong inhibitory effect on the photochemical isomerization of resveratrol and significantly limits the formation of the toxic derivative THP. Considering the presence of resveratrol in various commercial products, these results are of note in view of the potential genotoxic risk associated with its photochemical degradation products and in view of the need for the development of green, eco-sustainable and biocompatible resveratrol photo-stable formulations.

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30

Ren, Miaofeng, Xiaoyang Yan, Xiaojing Lai, Jin-Biao Liu, Hongwei Zhou e Guanyinsheng Qiu. "Nitrenium ion-based ipso-addition and ortho-cyclization of arenes under photo and iron dual-catalysis". Molecular Catalysis 528 (agosto 2022): 112413. http://dx.doi.org/10.1016/j.mcat.2022.112413.

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31

In-Seop-Cho, Chao-Pin Lee e Patrick S. Mariano. "Stereochemical aspects of photo-set induced diradical cyclization reactions as part of isoquinoline alkaloid synthetic strategies". Tetrahedron Letters 30, n. 7 (gennaio 1989): 799–802. http://dx.doi.org/10.1016/s0040-4039(01)80617-1.

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32

Warzecha, K. D., X. Xing e M. Demuth. "Cyclization of terpenoid polyalkenes via photo-induced electron transferversatile single-step syntheses of mono- and polycycles". Pure and Applied Chemistry 69, n. 1 (1 gennaio 1997): 109–12. http://dx.doi.org/10.1351/pac199769010109.

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33

Moormann, Widukind, Daniel Langbehn e Rainer Herges. "Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials". Beilstein Journal of Organic Chemistry 15 (20 marzo 2019): 727–32. http://dx.doi.org/10.3762/bjoc.15.68.

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Abstract (sommario):

Seven symmetrically 3,3’-substituted diazocines were synthesized. Functional groups include alcohol, azide, amine and vinyl groups, which are suitable for polymer synthesis. Upon irradiation at 385 and 530 nm the diazocines perform a reversible, pincer-type movement switching the 3,3’-distance between 6.1 Å (cis, stable isomer) and 8.2 Å (trans, metastable isomer). Key reactions in the synthesis are an oxidative C–C coupling of 2-nitrotoluenes (75–82% yield) and a reductive ring closure to form the diazocines (56–60% yield). The cyclization of the dinitro compound to the azo compound was improved in yield and reproducibility, by over-reduction to the hydrazine and reoxidation to the azo unit. In contrast to 3,3’- and 4,4’-diaminodiazocine, which have been implemented in macromolecules for conformation switching, our compounds exhibit improved photophysical properties (photostationary states, separation of absorption bands in the cis and trans configuration). Hence they are promising candidates as molecular switches in photo and mechanoresponsive macromolecules and other smart materials.

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34

Singh, Ravinder, Hsin-Yen Wu, Atul Kumar Dwivedi, Ashutosh Singh, Chien-Min Lin, Putikam Raghunath, Ming-Chang Lin, Tung-Kung Wu, Kung-Hwa Wei e Hong-Cheu Lin. "Monomeric and aggregation emissions of tetraphenylethene in a photo-switchable polymer controlled by cyclization of diarylethene and solvent conditions". Journal of Materials Chemistry C 5, n. 38 (2017): 9952–62. http://dx.doi.org/10.1039/c7tc03071a.

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35

He, Shang Hua, Gang Liu e Shi Qiang Cui. "Study on Photochromic Materials with a Novel Photochromic Diarylethene use for Polarization Holographic Recording". Advanced Materials Research 763 (settembre 2013): 61–64. http://dx.doi.org/10.4028/www.scientific.net/amr.763.61.

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Abstract (sommario):

A novel unsymmetrical photochromic diarylethene 1-(2, 5-dimethyl-3-thienyl)-2-[2-methyl-5-(2,2-dibutylfluorene)-3-thienyperfluorocyclo-pentene (1o) was synthesized and its photochromic and fluorescent properties were investigated. Diarylethene 1 changed the color from colorless to hyacinthine upon irradiation with 297 nm UV light, in which absorption maxima were observed at 554 nm in hexane and at 565 nm in PMMA amorphous film, respectively. This new photochromic system also exhibited remarkable fluorescence intensity both in solution and in PMMA film. The fluorescence spectra showed a systematic red-shift with the emission intensity of diarylethene 1 in a photo-stationary state was quenched to ca. 64%. The cyclization and cycloreversion quantum yields of 1 in hexane were determined to be 0.56 and 0.002. Polarization multiplexed image recording can be carried out in this diarylethene 1c/PMMA film as recording medium film.

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36

Migliorini, M. G., P. Galvan, G. Sbrana, G. P. Donzelli e C. Vecchi. "Bilirubin photoconversion induced by monochromatic laser radiation. Comparison between aerobic and anaerobic experiments in vitro". Biochemical Journal 256, n. 3 (15 dicembre 1988): 841–46. http://dx.doi.org/10.1042/bj2560841.

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Structural and geometric photoisomerization of bilirubin bound to human serum albumin was investigated. Solutions were irradiated with monochromatic light emitted by an Ar ion laser, the 457.9, 488.0 and 514.5 nm wavelengths being selected. Photoproducts were separated and analysed by h.p.l.c. Visible-absorption spectra of pure ZZ-bilirubin, ZE-bilirubin and lumirubin in the eluent were registered in the 350-550 nm region by collecting single fractions by h.p.l.c. Wavelength-dependence of bilirubin photoconversion was studied within photoequilibrium and up to a large decrement of the total concentration. Experiments were performed in aerobic and anaerobic conditions in order to assess the contribution of the photo-oxidation to the overall process. The presence of O2 was found to increase the rate of bilirubin degradation and unexpectedly to favour lumirubin production. The ability of 514.5 nm irradiation to induce bilirubin cyclization was definitively confirmed.

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37

Zou, Long, Lei Wang, Li Sun, Xiaofei Xie e Pinhua Li. "Photo-driven haloazidation cyclization of 1,5-enynes having cyano groups with TMSN3 and NIS/NCS/NBS under metal-free conditions". Chemical Communications 56, n. 57 (2020): 7933–36. http://dx.doi.org/10.1039/d0cc02471f.

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Abstract (sommario):

A visible-light-driven three-component haloazidation cyclization of 1,5-enynes having cyano groups with TMSN₃ and N-iodo(bromo/chloro)succinimide (NIS/NCS/NBS) under metal-free conditions was developed.

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38

Grondin, Joseph, Christian Aupetit, Jean-Marc Vincent e Thierry Tassaing. "Cyclic Carbonates through the Photo-Induced Carboxylative Cyclization of Allylic Alcohol with CO2: A Comprehensive Kinetic Study of the Reaction Mechanism by In Situ ATR-IR Spectroscopy". Catalysts 13, n. 6 (26 maggio 2023): 939. http://dx.doi.org/10.3390/catal13060939.

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A one-pot multicomponent green process is investigated for the synthesis of perfluoroalkylated cyclic carbonate which merges the photo-promoted Atom Transfer Radical Addition (ATRA) of a perfluoroalkyl iodide (Rf-I) onto allyl alcohols with the Lewis-base-promoted carboxylative cyclization. The evolution of the complex mixture during the reaction was monitored by in situ ATR-IR and Raman spectroscopies that provided insights into the reaction mechanism. The effect on the kinetics and the carbonate yields of key parameters such as the stoichiometry of reagents, the nature of the Lewis base and the solvent, the temperature and the pressure were evaluated. It was found that high yields were obtained using strong Lewis bases that played both the role of activating the allyl alcohol for the generation of the allyl carbonate in the presence of CO2 and promoting the ATRA reaction through the activation of C4F9I by halogen bonding. This protocol was also extended to various unsaturated alcohols.

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39

Huang, Michael H. "(Invited) Semiconductor Facet Effects Toward Photocatalysis". ECS Meeting Abstracts MA2024-01, n. 13 (9 agosto 2024): 1078. http://dx.doi.org/10.1149/ma2024-01131078mtgabs.

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Abstract (sommario):

Photo-induced charge transfer has been found to strongly depend on the exposed semiconductor surfaces. For instance, {110}-bound Cu2O rhombic dodecahedra exhibit a high photocatalytic activity toward dye degradation, but {100}-terminated Cu2O cubes are inert. Photocatalytic behaviors of Cu2O-based semiconductor heterostructures, such as Cu2O-ZnS and Cu2O-ZnO composites, can both enhance and suppress photocatalytic activity depending on the contacting planes at the heterojunction. Significantly, Cu2O photocatalytic activity can be greatly enhanced by functionalizing with conjugated molecules such as 4-nitrophenylacetylene (4-NA) to tune the surface band structure. This can turn the inactive cubes to possess a superior photocatalytic activity. Recently, Cu2O rhombic dodecahedra with and without 4-NA modification have been employed in photocatalytic hydroxylation of boronic acids, aryl sulfide oxidation, and amine coupling. SrTiO3 truncated rhombic dodecahedra were also found to be effective in amine coupling. Oxidative cyclization of thioamides is the latest example of surface control to photocatalytic organic transformations.

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40

Sun, Bin, Hao Ding, Hai‐Xia Tian, Pan‐Yi Huang, Can Jin, Chun‐Lei Wu e Run‐Pu Shen. "Photo‐Triggered Self‐Induced Homolytic Dechlorinative Sulfonylation/Cyclization of Unactivated Alkenes: Synthesis of Quinazolinones Containing a Sulfonyl Group". Advanced Synthesis & Catalysis 364, n. 4 (16 dicembre 2021): 766–72. http://dx.doi.org/10.1002/adsc.202101141.

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41

Campos, Pedro J., Míriam Caro e Miguel A. Rodríguez. "Role of the electron-donating methoxy group on the photo-induced cyclization of 2-azadienes: a mechanistic study". Tetrahedron 69, n. 37 (settembre 2013): 7950–55. http://dx.doi.org/10.1016/j.tet.2013.07.015.

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42

Keshari, Twinkle, Vishnu P. Srivastava e Lal Dhar S. Yadav. "Visible-light-initiated photo-oxidative cyclization of phenolic amidines using CBr4 – A metal free approach to 2-aminobenzoxazoles". RSC Advances 4, n. 11 (2014): 5815. http://dx.doi.org/10.1039/c3ra46314a.

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43

Leitich, Johannes, Ingeborg Heise, Jürgen Rust e Kurt Schaffner. "The Photo-Nazarov Cyclization of 1-Cyclohexenyl(phenyl)methanone Revisited − Trapping of the 2-Oxyallyl Intermediates by Olefins". European Journal of Organic Chemistry 2001, n. 14 (luglio 2001): 2719–26. http://dx.doi.org/10.1002/1099-0690(200107)2001:14<2719::aid-ejoc2719>3.0.co;2-z.

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44

Nagasaka, Tatsuhiro, Hikaru Sotome, Soichiro Morikawa, Lucas Martinez Uriarte, Michel Sliwa, Tsuyoshi Kawai e Hiroshi Miyasaka. "Restriction of the conrotatory motion in photo-induced 6π electrocyclic reaction: formation of the excited state of the closed-ring isomer in the cyclization". RSC Advances 10, n. 34 (2020): 20038–45. http://dx.doi.org/10.1039/d0ra03523h.

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45

Yang, Chen, Faisal Mehmood, Tsz Lung Lam, Sharon Lai-Fung Chan, Yuan Wu, Chi-Shun Yeung, Xiangguo Guan et al. "Stable luminescent iridium(iii) complexes with bis(N-heterocyclic carbene) ligands: photo-stability, excited state properties, visible-light-driven radical cyclization and CO2 reduction, and cellular imaging". Chemical Science 7, n. 5 (2016): 3123–36. http://dx.doi.org/10.1039/c5sc04458h.

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46

Polukhtine, Andrei, Grigori Karpov, Dinesh R. Pandithavidana, Alexander Kuzmin e Vladimir V. Popik. "Photochemical Triggering of the Bergman and Myers - Saito Cyclizations". Australian Journal of Chemistry 63, n. 7 (2010): 1099. http://dx.doi.org/10.1071/ch10185.

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Abstract (sommario):

Two strategies for the photochemical generation of reactive enediyne compounds and their subsequent cycloaromatization to p-benzyne or α,3-didehydrotoluene derivatives are discussed in this account. The first method employs a photo-Wolff reaction of stable 11- or 12-membered ring precursor enediynes containing the 2-diazo-1,3-diketone moiety. Irradiation of these compounds results in ring contraction and the formation of two isomeric enediynes possessing an enolized β-ketoester fragment. One of the isomers undergoes the conventional Bergman cyclization, whereas the other isomerizes into the enyne-allene tautomer, which rapidly cyclizes via a Myers–Saito mechanism. The second strategy consists of replacing the triple bond in a cyclic enediyne or enyne-allene structure with a cyclopropenone group, rendering them thermally stable. Photolysis of cyclopropenones results in efficient decarbonylation and the regeneration of a triple bond, restoring the enediyne π-system. The generation of reactive enediynes by non-resonant two-photon excitation using wavelengths within a ‘phototherapeutic window’ was also demonstrated. Photogenerated enediynes show significant nuclease activity, efficiently inducing single-strand dDNA cleavage.

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47

Keshari, Twinkle, Vishnu P. Srivastava e Lal Dhar S. Yadav. "ChemInform Abstract: Visible-Light-Initiated Photo-Oxidative Cyclization of Phenolic Amidines Using CBr4- A Metal Free Approach to 2-Aminobenzoxazoles." ChemInform 45, n. 40 (18 settembre 2014): no. http://dx.doi.org/10.1002/chin.201440144.

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48

Wonanke, A. D. Dinga, e Deborah L. Crittenden. "Beyond the Woodward-Hoffman Rules: What Controls Reactivity in Eliminative Aromatic Ring-Forming Reactions?" Australian Journal of Chemistry 71, n. 4 (2018): 249. http://dx.doi.org/10.1071/ch17564.

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Abstract (sommario):

The Mallory (photocyclization) and Scholl (thermal cyclohydrogenation) reactions are widely used in the synthesis of extended conjugated π systems of high scientific interest and technological importance, including molecular wires, semiconducting polymers, and nanographenes. While simple electrocyclization reactions obey the Woodward-Hoffman rules, no such simple, general, and powerful model is available for eliminative cyclization reactions due to their increased mechanistic complexity. In this work, detailed mechanistic investigations of prototypical reactions reveal that there is no single rate-determining step for thermal oxidative dehydrogenation reactions, but they are very sensitive to the presence and distribution of heteroatoms around the photocyclizing ring system. Key aspects of reactivity are correlated to the constituent ring oxidation potentials. For photocyclization reactions, planarization occurs readily and/or spontaneously following photo-excitation, and is promoted by heteroatoms within 5-membered ring adjacent to the photocyclizing site. Oxidative photocyclization requires intersystem crossing to proceed to products, while reactants configured to undergo purely eliminative photocyclization could proceed to products entirely in the excited state. Overall, oxidative photocyclization seems to strike the optimal balance between synthetic convenience (ease of preparation of reactants, mild conditions, tolerant to chemical diversity in reactants) and favourable kinetic and thermodynamic properties.

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49

Рязанцева, Тетяна. "MEMORY AND TIME IN OLES ILCHENKO’S PHOTOPOETRY". Слово і Час, n. 3 (30 giugno 2024): 19–35. http://dx.doi.org/10.33608/0236-1477.2024.03.19-35.

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Abstract (sommario):

The paper considers new creative approaches to the established types of poetry. Building on the theoretical definitions, taxonomies and observations formulated in the works of Aleida Assmann, Roland Barthes, Nina Chamata, Robert Crawford and Norman McBeath, Michael Nott, Irina Rajewski, James Smith, Susan Sontag, et al., the research argues that the artistic practices of photopoetry (“a form of photo-text that takes, for its primary components, poetry and photography”, Michael Nott) offer new ways to interpret certain topics of metaphysical poetry. The material for analysis is taken from a black and white photo-text book “Some Dreams or Kyiv That No Longer Exists” (2007) by a Geneva-based Ukrainian poet and artist Oles Ilchenko. The detailed analysis of it seeks to clarify the structural, stylistic, and semantic characteristics of Ilchenko’s photopoetry. The special attention is paid to the mechanics of cyclization, forms of intermedial interactions, and types of artistic collaboration in this project. It is also noted that the interpretative co-operation with the audience here depends on the readers/viewers’ personal memories and emotions evoked by these photographs and poems. Focusing on the motifs of memory, nostalgia, and transience of life, Ilchenko’s photopoetic cycle explores the metaphysical theme of Death and Time in its connection with the urban space of Kyiv. This project demonstrates that the long form photopoetry provides the 21st century author with some efficient creative instruments to interpret the realities “of peculiar kind” (James Smith), such as time and memory. The contrasting combination of verbal and visual elements in this book creates an effect of double visualization, which accentuates the dynamics and dramatic tension between the poems and the images. The cyclic composition of texts paired with the fragmented and modified photographs transforms the real urban space into a powerful metaphor of memory and personal loss.

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50

Zhang, Yunxiao, Jiaxin Wang, Youyuan Guo, Shanshan Liu e Xiao Shen. "Carbonyl Olefin Metathesis and Dehydrogenative Cyclization of Aromatic Ketones and gem‐Difluoroalkenes". Angewandte Chemie, 8 dicembre 2023. http://dx.doi.org/10.1002/ange.202315269.

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Abstract (sommario):

The beauty of one‐pot cascade reaction lies in the efficient disconnection and construction of several bonds in a single reaction flask, without the isolation of any intermediates. Herein, we report the first photo‐induced thermal‐promoted cascade reactions of readily available aromatic ketones and aromatic gem‐difluoroalkenes for the synthesis of phenanthrenes which possess potential utility in drug design and material science. The reaction combines carbonyl‐olefin metathesis (cascade photo‐induced [2+2] cyclization and thermal‐controlled retro [2+2] cyclization) and dehydrogenative cyclization (cascade photo‐induced conrotatory 6π electrocyclization and collidine‐promoted dehydrogenative aromatization) together in one pot. The oxidant‐free, acid‐free and metal‐free reaction shows broad substrate scope and wide functional group tolerance.

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