- Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides
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We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated in situ. The combination of an isophthalonitrile photocatalyst and sodium formate promotes diverse aryl radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.
- Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.,Williams, Oliver P.,Yeung, Charles S.
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supporting information
p. 10882 - 10889
(2021/07/31)
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- Amphipathic sulfonamidobenzamides mimicking small antimicrobial marine natural products; investigation of antibacterial and anti-biofilm activity against antibiotic resistant clinical isolates
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There is an urgent need for novel antimicrobial agents to address the threat of bacterial resistance to modern society. We have used a structural motif found in antimicrobial marine hit compounds as a basis for synthesizing a library of antimicrobial sulf
- Igumnova, Elizaveta M.,Mishchenko, Ekaterina,Haug, Tor,Blencke, Hans-Matti,Sollid, Johanna U. Ericson,Fredheim, Elizabeth G. Aarag,Lauksund, Silje,Stensv?g, Klara,Str?m, Morten B.
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p. 4930 - 4941
(2018/09/11)
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- Investigation of oxygen-free Sonogashira step growth synthesis of mono-terminated di-tert-butyl-substituted oligo(phenylene ethynylene)s (OPEs)
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A series of oligomers, the hetero-coupled mono-terminated di-tert-butyl-substituted phenylene ethynylene dimer, trimer, tetramer, and pentamer have been successfully synthesized in a stepwise process and characterized. Their electronic properties have bee
- Bai, Xinyan,Chen, Xueyi,Barnes, Charles,Dias, Jerry R.,Sandreczki
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p. 1105 - 1111
(2013/02/23)
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- Microwave mediated protection of hindered phenols and alcohols
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Hindered phenols and alcohols were protected as their corresponding ethers using different alkylating agents in presence of KOH/DMSO under microwave irradiation.
- Pothi, Tejas,Dawange, Mahesh,Chavan, Kamlesh,Sharma, Rajiv,Deka, Nabajyoti
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p. 706 - 711
(2013/03/28)
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- Easier preparation of 2,6-Di-tert-butylphenyl derivatives 1
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Despite steric shielding by the 2,6-di-tert-butylphenyl group (super-2,6-xylyl=xyl*), inexpensive sodium phenolate (xyl*-ONa) reacts with dimethyl sulfate to produce only xyl*-OCH3 (94%) with complete suppression of the alternative 4-methylation. Reductive cleavage of xyl*-OCH3 by elemental lithium with the help of an electron carrier generates xyl*-Li, which in turn yields xyl*-CO2H (63%). The corresponding 4-methyl-derivatives of these compounds were obtained analogously. The acid chloride xyl*-COCl (77% yield) acylates HalMgCH 2R to give only xyl*-COCH3 (86%) or xyl*-COEt (97%). These two ketones react with n-butyllithium (no carbonyl addition) and Cl-PO(OEt)2 to furnish only the enol phosphates xyl*-C(=CH 2)OPO(OEt)2 (84%) or xyl*-C(=CHCH 3)OPO(OEt)2 (up to 70%), respectively. Only 1,2-elimination occurs when the latter two products are treated with tert-butyllithium, affording xyl*-CCH (68%) or xyl*-CCMe (88%), respectively. Georg Thieme Verlag Stuttgart - New York.
- Knorr, Rudolf,Rossmann, Eva Christine,Knittl, Monika
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experimental part
p. 2124 - 2128
(2010/09/04)
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- Pyridine, Pyrimidine and Pyrazine Derivatives as Cxcr3 Receptor Modulators
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The invention encompasses compounds of Formula I or pharmaceutically acceptable salts thereof, which are modulators of the CXCR3 chemokine receptor function useful for the treatment or prevention of pathogenic inflammatory processes, autoimmune diseases o
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Page/Page column 15
(2009/02/11)
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- Syntheses of sterically hindered zwitterionic pyridinium phenolates as model compounds in nonlinear optics
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Pyridinium phenolates possess a dissymmetric delocalised π-electron system providing a huge quadratic nonlinearity. They are a promising class of molecules for applications in photoelectronics and photonics. Semiempirical calculations indicate that the interplanar angle between the two aromatic rings leads to enhancement in the NLO properties of these compounds. The confirmation of this feature may be provided by the study of a new series of sterically hindered pyridinium phenolates 2a-e bearing two tert-butyl substituents at the ortho position(s) of the phenolate functionality. Such bulky groups would enhance the solubility of zwitterions in organic solvents and would limit the formation of aggregates. Their efficient preparations by using Suzuki cross-coupling reactions involving 3,5-dialkylated 4-bromopyridine N-oxides are described herein. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Diemer, Vincent,Chaumeil, Helene,Defoin, Albert,Fort, Alain,Boeglin, Alex,Carre, Christiane
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experimental part
p. 1767 - 1776
(2009/04/11)
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- Highly Diastereoselective Intermolecular β-Addition of Alkyl Radicals to Chiral 2-(Arylsulfinyl)-2-cycloalkenones
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The diastereoselectivity of intermolecular β-addition of alkyl radicals to 2-(arylsulfinyl)-2-cycloalkenones depends largely upon the structure of the arylsulfinyl group. The reaction of 2-cyclopentenones or 2-cyclohexenones having a sterically bulky arylsulfinyl group such as (3,5-di-tert-butyl-4-methoxyphenyl)sulfinyl, (2,4,6-triisopropylphenyl)sulfinyl or (2,4,6-trimethylphenyl)sulfinyl group gives 3-alkyl-2-(arylsulfinyl)-1-cyclopentanones or 3-alkyl-2-(arylsulfinyl)-1-cyclohexanones in excellent yields and with high diastereoselectivity. Both the X-ray crystallographic analysis and the NOE experiment in the 1H NMR spectrum of (S)-2-[(2,4,6-triisopropylphenyl)sulfinyl]- and (S)-2-[(2,4,6-trimethylphenyl)sulfinyl]-2-cyclopentenone reveal an effective shielding of one of the olefin faces at the β-position by o-isopropyl and o-methyl groups. The addition of bidentate Lewis acids reverses the stereoselection through chelating the intermediates to give the addition products with high diastereoselectivity.
- Mase, Nobuyuki,Watanabe, Yoshihiko,Ueno, Yoshio,Toru, Takeshi
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p. 7794 - 7800
(2007/10/03)
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- Factors Influencing the Acid Lability of Substituted Arylsulphonyl Arginine Protecting Groups
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The kinetics of hydrolysis of new, NG-protected 2,4,6-triisopropylbenzene-sulphonyl (6), 4-methoxy-3,5-di-tert-butylbenzenesulphonyl (12) and phenanthrene-3-sulphonyl (17) Fmoc derivatives of L-arginine (1) in comparison with commercially available Fmoc-Arg(Mtr)-OH (Mtr = 4-methoxy-2,3,6-trimethyl-benzenesulphonyl (2)) are studied.The acid lability of the arylsulphonyl group is decreasing as follows Mtr > Tip > Mtbs > Phen.The effect of electron-donating alkyl groups as substituents in increasing the acid lability of the arylsulphonyl residue seems to be in the order of methyl > isopropyl > tert-butyl, while the effect of extended delocalization does not appreciably increase the acid lability. - Keywords: 2,4,6-Triisopropylbenzenesulphonyl (Tip), 4-methoxy-3,5-di-tert-butylbenzenesulphonyl (Mtbs), Phenanthrene-3-sulphonyl (Phen) Residues
- Ali, Syed Safdar,Echner, Hartmut,Khan, Khalid Mohammed,Schroeder, Christoph,Hasan, Mashooda,et al.
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p. 1425 - 1433
(2007/10/02)
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- Enhancement of the Resonance Interaction of Out-of-Plane Methoxy Groups By Ortho Substituents in Crowded Anisoles
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The 17O and 13C NMR chemical shifts of substituted anisoles provide evidence that the resonance interaction of methoxy groups which are perpendicular to the aromatic ring in crowded anisoles is influenced, to varying degrees, by ortho substituents.Enhance
- Schuster, Ingeborg I.,Parvez, Masood,Freyer, Alan J.
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p. 5819 - 5825
(2007/10/02)
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- Molecular Orbital Calculations and 13C NMR Studies To Explain a Regiospecific Demethylation of 3-Alkyl-1,2-dimethoxybenzenes
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This study was performed to explain a regiospecific demethylation of 3-alkyl-1,2-dimethoxybenzenes.PRDDO-MO calculations show that the low-energy conformation of the carbon of a methoxy group having two ortho neighbors on a benzene ring is located out of the plane of the aromatic ring, whereas a methoxy group with only one ortho neighbor executes restricted rotation in the plane of the ring.The carbon portion of the methoxy group is turned away from the neighboring substituent.These calculations also show that the atomic charge on the oxygen atom in the former caseexceeds that in the latter.The carbon of a methoxy group with two ortho neighbors yields 13C NMR T1 relaxation times longer than those with only one ortho neighbor, also suggesting that the methoxy group with two ortho neighbors is crowded out of the plane of the aromatic ring. 13C NMR chemical shifts of these ortho-substituted methoxybenzenes did not correlate well with shifts predicted from published additive parameters; this again suggests an unusual methoxy group orientation and distribution of electrons.The forced rotation of a methoxy group out of the plane of the benzene ring diminishes the release of electrons from the methoxy group to the benzene ring.The resulting higher atomic charge on the oxygen and the orientation of the oxygen orbitals facilitate complexation with Lewis acids and methoxy group cleavage.
- Jardon, Phillip W.,Vickery, Euin H.,Pahler, Leon F.,Pourahmady, Naser,Mains, Gilbert J.,Eisenbraun, Edmund J.
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p. 2130 - 2135
(2007/10/02)
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- AGGREGATION OF LITHIUM PHENOLATES IN WEAKLY POLAR APROTIC SOLVENTS.
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The aggregation of lithium phenolate, 3,5-dimethylphenolate, 2,6-dimethylphenolate, and 2,6-di-tert-butylphenolate in dioxalane, dimethoxyethane, and pyridine has been investigated by a variety of methods including studies of vapor pressure barometry, **1**3C chemical shifts, **7Li nuclear quadrupole coupling constants, and **1**3C spin-lattice relaxation times. The phenolates with no ortho substituents from tetramers under most conditions. In pyridine at low concentrations and temperature the tetramers coexist with dimers. Lithium 2,6-dimethylphenolate forms dimers under all conditions studied, and lithium 2,6-di-tert-butylphenolate exists as a monomer or an oligomer depending on conditions. Attempts to establish solvation numbers for the aggregates from solvent **1**3C relaxation times have not been successful, and the reason for the failure, very fast solvent exchange, is discussed. The kinetics and thermodynamics of exchange between dimers and tetramers of lithium 3,5-dimentylphenolate in pyridine have been investigated, and the mechanism of interconversion is shown to involve additional solvation of the tetramer prior to dissociation.
- Jackman,DeBrosse
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p. 4177 - 4184
(2007/10/02)
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- FLUORIDE SALTS ON ALUMINA AS REAGENTS FOR ALKYLATION OF PHENOLS AND ALCOHOLS.
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THE EFFECTIVENESS OF ALKALI METAL FLUORIDES IMPREGNATED ON ALUMINA AS A REAGENT FOR PROMOTING ALKYLATION WAS OPTIMIZED WITH RESPECT TO THE METAL CATION, THE AMOUNT OF IMPREGNATION, AND THE REACTION SOLVENT. POTASSIUM OR CAESIUM FLUORIDE ONALUMINA IN ACETONITRILE OR 1,2-DIMETHOXYETHANE WAS CONCLUDED TO BE THE BEST REACTION SYSTEM FOR GENERAL USE. O-ALKYLATION OF SUBSTITUTED PHENOLS, PRIMARY AND SECONDARY ALCOHOLS, AND A GLYCOL WAS CARRIED OUT MOSTLY IN GOOD YIELDS UNDER MILDCONDITIONS WITH SIMPLE EXPERIMENTAL PROCEDURES.
- ANDO,YAMAWAKI,KAWATE,SUMI,HANAFUSA
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p. 2504 - 2507
(2007/10/02)
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- Synthesis of Substituted Dibenzophospholes. Part 2. Syntheses of Intermediate Biphenyls and Quaterphenyls
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A general procedure for synthesis of 4",6'-dialkoxy-2',2"-diamino-m-quaterphenyls has been established.Copper(I) t-butoxide is used to prepare 2,6-dinitrophenyls from 1,3-dinitrobenzene and aryl iodides.One of the nitro-groups is then exchanged for a methoxy-group by sodium methoxide in hexamethylohosphoramide; the resulting 2-methoxy-6-nitrobiphenyls are then iodinated in the 5-position.Ullmann coupling then gives the dinitroquaterphenyls which are reduced to the diamines.An alternative route from 2,2',4,4'-tetranitrobiphenyl was explored; arylation was easy but alkoxydenitration was indiscriminate.Some 71 new derivatives of biphenyl, terphenyl, and quterphenyl are reported.
- Cornforth, John,Sierakowski, Andrew F.,Wallace Timothy W.
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p. 2299 - 2316
(2007/10/02)
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