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You searched for: Subject term irradiation Remove constraint Subject term: irradiation Subject term stereochemistry Remove constraint Subject term: stereochemistry
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1. Advances in the E → Z Isomerization of Alkenes Using Small Molecule Photocatalysts

Author:
Tomáš Neveselý; Max Wienhold; John J. Molloy; Ryan Gilmour
Source:
Chemical reviews 2021 v.122 no.2 pp. 2650-2694
ISSN:
1520-6890
Subject:
alkenes; catalytic activity; cis-trans isomerism; energy transfer; fabrics; irradiation; photocatalysts; photochemistry; photosensitivity; regioselectivity; stereochemistry; stereospecificity
Abstract:
... Geometrical E → Z alkene isomerization is intimately entwined in the historical fabric of organic photochemistry and is enjoying a renaissance (Roth et al. Angew. Chem., Int. Ed. Engl. 1989 28, 1193–1207). This is a consequence of the fundamental stereochemical importance of Z-alkenes, juxtaposed with frustrations in thermal reactivity that are rooted in microscopic reversibility. Accessing excite ...
DOI:
10.1021/acs.chemrev.1c00324

2. On-Demand Chirality Transfer of Human Serum Albumin to Bis(thiophen-2-yl)hexafluorocyclopentenes through Their Photochromic Ring Closure

Author:
Yuri Saeki; Megumi Kayanuma; Aki Nitta; Yasuteru Shigeta; Izuru Kawamura; Tetsuya Nakagawa; Takashi Ubukata; Yasushi Yokoyama
Source:
Journal of organic chemistry 2021 v.86 no.18 pp. 12549-12558
ISSN:
1520-6904
Subject:
carbon; dicarboxylic acids; enantioselectivity; esterification; esters; human serum albumin; irradiation; molecular dynamics; optical isomerism; organic chemistry; stereochemistry
Abstract:
... Photochromic 1,2-bis(5-carboxy-3-methyl-2-thienyl)hexafluorocyclopentene and its dimethyl ester incorporated in human serum albumin (HSA) showed highly enantioselective photochromic ring-closing reactions upon 366 nm light irradiation. The absolute stereochemistry of the major ring-closed form of the dicarboxylic acid at the newly formed sp³ carbon atoms was determined to be (S,S) by the process o ...
DOI:
10.1021/acs.joc.1c00849

3. A Change from Kinetic to Thermodynamic Control Enables trans-Selective Stereochemical Editing of Vicinal Diols

Author:
Yu-An Zhang; Xin Gu; Alison E. Wendlandt
Source:
Journal of the American Chemical Society 2021 v.144 no.1 pp. 599-605
ISSN:
1520-5126
Subject:
blue light; catalysts; chemoselectivity; glycols; hydrogen; irradiation; isomerization; redox reactions; stereochemistry; thermodynamics
Abstract:
... Here, we report the selective, catalytic isomerization of cis-1,2-diols to trans-diequatorial-1,2-diols. The method employs triphenylsilanethiol (Ph₃SiSH) as a catalyst and proceeds under mild conditions in the presence of a photoredox catalyst and under blue light irradiation. The method is highly chemoselective, broadly functional group tolerant and provides concise access to trans-diol products ...
DOI:
10.1021/jacs.1c11902

4. One new sesquiterpene and one new iridoid derivative from Valeriana amurensis

Author:
Yang-Guo Xie; Xin-Cai Zhao; Syed Shams ul Hassan; Xiao-Yong Zhen; Ishaq Muhammad; Shi-kai Yan; Xing Yuan; Hui-liang Li; Hui-zi Jin
Source:
Phytochemistry letters 2019 v.32 pp. 6-9
ISSN:
1874-3900
Subject:
Valeriana; X-ray diffraction; anti-inflammatory activity; inhibitory concentration 50; irradiation; macrophages; nitric oxide; sesquiterpenoids; spectral analysis; stereochemistry
Abstract:
... One new sesquiterpene 1S, 3S, 4S, 7S 3,4-dihydroxy-bisabolol (1), one new iridoid amurensin A (2) and 10 known compounds were isolated from the whole plants of Valeriana amurensis. Their structures were established on the basis of extensive spectroscopic analysis and the absolute stereochemistry of compound 1 was assigned by X-ray diffraction analysis with Cu-Kα irradiation. All of compounds were ...
DOI:
10.1016/j.phytol.2019.04.020

5. Revisiting the photochemical synthesis of [FeFe]-hydrogenase mimics: reaction optimization, mechanistic study and electrochemical behaviour

Author:
Sergio Aguado; Luis Casarrubios; Carmen Ramírez de Arellano; Miguel A. Sierra
Source:
RSC advances 2020 v.10 no.50 pp. 29855-29867
ISSN:
2046-2069
Subject:
alkynes; cycloaddition reactions; electrochemistry; irradiation; olefin; photochemical reactions; stereochemistry
Abstract:
... The photoreaction of [(μ-S)₂Fe₂(CO)₆] and alkenes or alkynes has been optimized to readily obtain functionalized [FeFe]-hydrogenase mimics. Irradiation under low CO pressure in THF produces the corresponding photo-adducts in good/acceptable (alkenes/alkynes) yields, with retention of the starting olefin stereochemistry. DFT-calculations provide plausible reaction pathways in both, singlet and trip ...
DOI:
10.1039/d0ra06002j

6. A new class of flavonoids bearing macrocyclic polyethers by stereoselective photochemical cycloaddition reaction

Author:
Hiroki Ishikawa; Naohiro Uemura; Ryo Taira; Kento Sano; Yasushi Yoshida; Takashi Mino; Yoshio Kasashima; Masami Sakamoto
Source:
Tetrahedron 2019 pp. -
ISSN:
0040-4020
Subject:
X-ray diffraction; chemical structure; cycloaddition reactions; dimerization; esters; flavonoids; irradiation; photolysis; stereochemistry; stereoselectivity
Abstract:
... A new class of flavonoids bearing cyclic polyethers involving a phenyl ring was conveniently provided by the intramolecular photochemical dimerization of 2-chromonecarboxylic esters. Irradiation of 2-chromonecarboxylate with a polyether tethered at both ends promoted intramolecular [2 + 2] cyclobutane formation leading to 14- to 27-membered cyclic polyethers. The efficiency depended on the substit ...
DOI:
10.1016/j.tet.2019.06.007

7. Multifunctional property exploration: Bi₄O₅I₂ with high visible light photocatalytic performance and a large nonlinear optical effect

Author:
Ruonan Yin; Yang Li; Kangdi Zhong; Hang Yao; Yamin Zhang; Kangrong Lai
Source:
RSC advances 2019 v.9 no.8 pp. 4539-4544
ISSN:
2046-2069
Subject:
irradiation; methyl orange; methylene blue; photocatalysis; photocatalysts; powders; rhodamines; stereochemistry
Abstract:
... Exploration of the versatility of materials is very important for increasing the utilization of materials. Herein, we successfully prepared Bi₄O₅I₂ powders via a facile solvothermal method. The Bi₄O₅I₂ photocatalyst exhibited significantly higher photocatalytic activity as compared to the common BiOI photocatalyst in the degradation of methyl orange, methylene blue and rhodamine B under visible li ...
DOI:
10.1039/c8ra08984a

8. Photocyclization of Tetra- and Pentapeptides Containing Adamantylphthalimide and Phenylalanines: Reaction Efficiency and Diastereoselectivity

Author:
Margareta Sohora; Mario Vazdar; Irena Sović; Kata Mlinarić-Majerski; Nikola Basarić
Source:
Journal of organic chemistry 2018 v.83 no.24 pp. 14905-14922
ISSN:
1520-6904
Subject:
amino acids; chemical structure; cyclic peptides; decarboxylation; diastereoselectivity; electron transfer; irradiation; molecular dynamics; organic chemistry; oxidation; photolysis; phthalimide; stereochemistry
Abstract:
... A series of tetrapeptides and pentapeptides was synthesized bearing a phthalimide chromophore at the N-terminus. The C-terminus of the peptides was strategically substituted with an amino acid, Phe, Phe(OMe), or Phe(OMe)₂ characterized by different oxidation potentials. The photochemical reactivity of the peptides was investigated by preparative irradiation and isolation of photoproducts, as well ...
DOI:
10.1021/acs.joc.8b01785

9. Stereochemistry in control of photochemical reactivity: 2,6-Diaryl-4H-spiro[cyclohexane-1,2′-indene]-1′,3′,4-triones

Author:
Vladimir Lokshin; Vladimir Khodorkovsky
Source:
Tetrahedron 2018 v.74 pp. 418-424
ISSN:
0040-4020
Subject:
chemical reactions; cis-trans isomers; cyclohexanones; irradiation; photochemistry; stereochemistry; wavelengths
Abstract:
... Photochemical reaction of trans-2,6-diaryl-4H-spiro[cyclohexane-1,2′-indene]-1′,3′,4-triones gives rise to the formation of the ylidenephthalide derivatives as previously observed for 2,2-disubstituted 1,3-indandiones. In contrast, the respective cis-isomers afford different products originating from the unprecedented reversible cyclohexanone cycle breaking (photo-induced retro-Michael reaction). ...
DOI:
10.1016/j.tet.2017.12.014

10. Total Synthesis of Zaragozic Acid C: Implementation of Photochemical C(sp3)–H Acylation

Author:
Kawamata Takahiro; Nagatomo Masanori; Inoue Masayuki
Source:
Journal of the American Chemical Society 2017 v.139 no.5 pp. 1814-1817
ISSN:
1520-5126
Subject:
acylation; irradiation; octane; squalene; stereochemistry
Abstract:
... Zaragozic acid C (1) was isolated as a potent squalene synthase inhibitor. The 2,8-dioxabicyclo[3.2.1]octane core of 1 is decorated with the three hydroxycarbonyl (C3,4,5), two hydroxy (C4,7), one acyloxy (C6), and one alkyl (C1) groups. Installation of the contiguous C4- and C5-fully substituted carbons presents a formidable synthetic challenge. Our approach to address this problem used a two-ste ...
DOI:
10.1021/jacs.6b13263

11. Substituent Directed Phototransformations of BN-Heterocycles: Elimination vs Isomerization via Selective B–C Bond Cleavage

Author:
Yang Deng-Tao; Mellerup Soren K.; Peng Jin-Bao; Wang Xiang; Li Quan-Song; Wang Suning
Source:
Journal of the American Chemical Society 2016 v.138 no.36 pp. 11513-11516
ISSN:
1520-5126
Subject:
boron; color; irradiation; isomerization; stereochemistry; ultraviolet radiation
Abstract:
... Electron-rich and -poor BN-heterocycles with benzyl-pyridyl backbones and two bulky aryls on the boron (Ar = tipp, BN-1, Ar = MesF, BN-2) have been found to display distinct molecular transformations upon irradiation by UV light. BN-1 undergoes an efficient photoelimination reaction forming a BN-phenanthrene with ΦPE = 0.25, whereas BN-2 undergoes a thermally reversible, stereoselective, and quant ...
DOI:
10.1021/jacs.6b07899

12. Synthesis and stereochemistry of cis-2,6-diphenyl-1-alkylpiperidines

Author:
H. Surya Prakash Rao; Elamvazhuthi Poonguzhali
Source:
Tetrahedron letters 2015 v.56 no.45 pp. 6190-6193
ISSN:
0040-4039
Subject:
amination; anisotropy; formates; irradiation; liquids; moieties; nuclear magnetic resonance spectroscopy; polyethylene; stereochemistry
Abstract:
... Facile and efficient synthesis of N-alkyl-2,6-diphenylpiperidines (NADPPs) was achieved by reductive amination cyclization (RAC) reaction on 1,5-diketones using alkylammonium formate. The reaction is a useful extension of classical Leuckart reductive amination. The RAC reaction is convenient and product isolation is simple when conducted under microwave (MW) irradiation in polyethylene glycol-200 ...
DOI:
10.1016/j.tetlet.2015.09.085

13. An Efficient Light-Driven P450 BM3 Biocatalyst

Author:
Tran Ngoc-Han; Nguyen Daniel; Dwaraknath Sudharsan; Mahadevan Sruthi; Chavez Garrett; Nguyen Angelina; Dao Thanh; Mullen Sarah; Nguyen Thien-Anh; Cheruzel Lionel E.
Source:
Journal of the American Chemical Society 2013 v.135 no.39 pp. 14484-14487
ISSN:
1520-5126
Subject:
biocatalysts; chemical bonding; cytochrome P-450; dodecanoic acid; electrons; enzymes; heme; hydroxylation; irradiation; photosensitizing agents; stereochemistry
Abstract:
... P450s are heme thiolate enzymes that catalyze the regio- and stereoselective functionalization of unactivated C–H bonds using molecular dioxygen and two electrons delivered by the reductase. We have developed hybrid P450 BM3 heme domains containing a covalently attached Ru(II) photosensitizer in order to circumvent the dependency on the reductase and perform P450 reactions upon visible light irrad ...
DOI:
10.1021/ja409337v
PubMed:
24040992
PubMed Central:
PMC3938315

14. Control of Conformer Population and Product Selectivity and Stereoselectivity in Competitive Photocyclization/Rearrangement of Chiral Donor–Acceptor Dyad

Author:
Nishiuchi Emi; Mori Tadashi; Inoue Yoshihisa
Source:
Journal of the American Chemical Society 2012 v.134 no.19 pp. 8082-8085
ISSN:
1520-5126
Subject:
irradiation; solvents; stereochemistry; temperature; wavelengths
Abstract:
... The conformer population and the relative excitation efficiency of each conformer, assessed by theoretical and experimental examinations, enabled us to precisely control the chemo- and diastereoselectivities of the competitive photocyclization/rearrangement reaction of a chiral donor–acceptor (D/A) dyad by irradiation wavelength, solvent polarity, and reaction temperature. Manipulating the ground- ...
DOI:
10.1021/ja302768w

15. Direct Determination of Absolute Molecular Stereochemistry in Gas Phase by Coulomb Explosion Imaging

Author:
Martin Pitzer; Maksim Kunitski; Allan S. Johnson; Till Jahnke; Hendrik Sann; Felix Sturm; Lothar Ph. H. Schmidt; Horst Schmidt-Böcking; Reinhard Dörner; Jürgen Stohner; Julia Kiedrowski; Michael Reggelin; Sebastian Marquardt; Alexander Schießer; Robert Berger; Markus S. Schöffler
Source:
Science 2013 v.341 no.6150 pp. 1096-1100
ISSN:
0036-8075
Subject:
X-ray diffraction; electrons; enantiomers; explosions; gases; image analysis; irradiation; stereochemistry
Abstract:
... Absolute Images Molecules are held together by a balance of charge between negative electrons and positive nuclei. When multiple electrons are expelled by laser irradiation, the remaining, mutually repulsive nuclei fly apart in a Coulomb explosion. Instead of traditional x-ray diffraction methods that require crystalline samples, Pitzer et al. (p. 1096) show that by tracking the fragment trajector ...
DOI:
10.1126/science.1240362

16. Direct evidence for the ring opening of monosaccharide anions in the gas phase: photodissociation of aldohexoses and aldohexoses derived from disaccharides using variable-wavelength infrared irradiation in the carbonyl stretch region

Author:
Darin J. Brown; Sarah E. Stefan; Giel Berden; Jeffrey D. Steill; Jos Oomens; John R. Eyler; Brad Bendiak
Source:
Carbohydrate research 2011 v.346 no.15 pp. 2469-2481
ISSN:
0008-6215
Subject:
absorption; aldohexoses; anions; aqueous solutions; disaccharides; dissociation; energy; gases; irradiation; photolysis; solvents; spectral analysis; stereochemistry; wavelengths
Abstract:
... All eight d-aldohexoses and aldohexoses derived from the non-reducing end of disaccharides were investigated by variable-wavelength infrared multiple-photon dissociation (IRMPD) as anions in the negative-ion mode. Spectroscopic evidence supports the existence of a relatively abundant open-chain configuration of the anions in the gas phase, based on the observation of a significant carbonyl absorpt ...
DOI:
10.1016/j.carres.2011.06.018

17. Chiral bis(amino acid)- and bis(amino alcohol)-oxalamide gelators. Gelation properties, self-assembly motifs and chirality effects

Author:
Leo Frkanec; Mladen Žinić
Source:
Chemical communications 2010 v.46 no.4 pp. 522-537
ISSN:
1364-548X
Subject:
Fourier transform infrared spectroscopy; amino acids; amino alcohols; chemical communication; crystal structure; enantiomers; fluorides; gelation; hydrogels; hydrogen bonding; irradiation; luminescence; mixing; nuclear magnetic resonance spectroscopy; optical isomerism; photoisomerization; solvents; stereochemistry; stilbenes; toluene; transmission electron microscopy
Abstract:
... Bis(amino acid)- and bis(amino alcohol)oxalamide gelators represent the class of versatile gelators whose gelation ability is a consequence of strong and directional intermolecular hydrogen bonding provided by oxalamide units and lack of molecular symmetry due to the presence of two chiral centres. Bis(amino acid)oxalamides exhibit ambidextrous gelation properties, being capable to form gels with ...
DOI:
10.1039/b920353m

18. Competitive isomerization and dimerization in co-crystals of 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol and sorbic acid: a new look at stereochemical requirements for [2+2] dimerization

Author:
Shao-Liang Zheng; Oanh Pham; Christophe M. L. Vande VeldeOn leave from: Department of Chemistry, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, Belgium. Current address: Laboratoire de Chimie des Polymères, Université Libre de Bruxelles, CP 206/1 Boulevard du Triomphe, 1050, Brussels, Belgium.; Milan Gembicky; Philip Coppens
Source:
Chemical communications 2008 v. no.22 pp. 2538-2540
ISSN:
1364-548X
Subject:
dimerization; irradiation; isomerization; photochemical reactions; sorbic acid; stereochemistry; stereospecificity; temperature; ultraviolet radiation
Abstract:
... Competitive [2+2] photodimerization and E→Z isomerization reactions occur in a co-crystal of 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol upon irradiation with 325 nm light. At 90 K both reactions are observed, whereas at 280 K the dimerization reaction is very fast and inhibits isomerization as the nature of the chromophore is affected by the reaction. The temperature dependence of the stereospecif ...
DOI:
10.1039/b802103a