- Photocatalyst-controlled and visible light-enabled selective oxidation of pyridinium salts
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This study proposes two different methods of photocatalytic-controlled and visible light-induced selective oxidation of pyridiniums with air as the terminal oxidant. The key to these transformations is to choose the appropriate light source and photocatal
- Peng, Xiang-Jun,He, Hai-Ping,Liu, Qian,She, Kun,Zhang, Bao-Qi,Wang, Heng-Shan,Tang, Hai-Tao,Pan, Ying-Ming
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p. 753 - 760
(2021/03/31)
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- Acid-Promoted Intramolecular Decarbonylative Coupling Reactions of Unstrained Ketones: A Modular Approach to Synthesis of Acridines and Diaryl Ketones
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Herein, we reported Lewis acid-or Br?nsted acid-promoted intramolecular C(sp2)-C(sp2) bond cleavage and a novel C(sp2)-C(sp2) bond-forming cascade reaction to synthesize the acridine motif. The metal-free oxidation of the alkyne motif generated the in situ ketone group extracted via a decarbonylation reaction. The mechanistic studies revealed that the electrophilic N-iodo species triggered key decarbonylation reactions via consecutive dearomatization/aromatization reactions. In addition, we exploited this acid-promoted C-C bond activation system with internal alkynes to synthesize bis(heteroaryl) ketones.
- Dhandabani, Ganesh Kumar,Shih, Chia-Ling,Wang, Jeh-Jeng
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supporting information
p. 1955 - 1960
(2020/03/04)
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- Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding
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Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3)?H] to ketones [C(sp2)=O] or esters [C(sp3)?O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine–enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD–DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.
- Guha, Somraj,Sekar, Govindasamy
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p. 14171 - 14182
(2018/09/10)
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- Palladium-Catalyzed Room-Temperature Acylative Suzuki Coupling of High-Order Aryl Borons with Carboxylic Acids
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This note describes a dimethyl dicarbonate-assisted, Pd(OAc)2/PPh3-catalyzed acylative Suzuki coupling of carboxylic acids with diarylborinic acids or tetraarylboronates for practical and efficient synthesis of sterically undemanding aryl ketones at room temperature. More than just cost-effective alternatives to aryl boronic acids, diarylborinic acids and tetraarylboronates displayed higher reactivity in the acylative Suzuki coupling. A variety of alkyl aryl ketones, including those bearing a hydroxy, bromo, or carbonyl group, could be readily obtained in modest to excellent yields.
- Si, Shufen,Wang, Chen,Zhang, Nan,Zou, Gang
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p. 4364 - 4370
(2016/06/09)
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- Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen
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The methylene group of various substituted 2- and 4-benzylpyridines, benzyldiazines and benzyl(iso)quinolines was successfully oxidized to the corresponding benzylic ketones using a copper or iron catalyst and molecular oxygen as the stoichiometric oxidant. Application of the protocol in API synthesis is exemplified by the alternative synthesis of a precursor to the antimalarial drug Mefloquine. The oxidation method can also be used to prepare metabolites of APIs which is illustrated for the natural product papaverine. ICP-MS analysis of the purified reaction products revealed that the base metal impurity was well below the regulatory limit.
- Sterckx, Hans,De Houwer, Johan,Mensch, Carl,Herrebout, Wouter,Tehrani, Kourosch Abbaspour,Maes, Bert U.W.
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supporting information
p. 144 - 153
(2016/04/05)
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- NOVEL ACRYLAMIDE DERIVATIVES AS ANTIMALARIAL AGENTS
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The invention relates to novel acrylamide derivatives of the formula (I) wherein R1, R 2, R 3, X, and ring A are as defined in the description, and their use as active ingredients in the preparation of pharmaceutical compo
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Page/Page column 72
(2014/09/29)
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- Tuning the redox chemistry of 4-benzoyl-N-methylpyridinium cations through para substitution. Hammett linear free energy relationships and the relative aptitude of the two-electron reduced forms for H-bonding
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In anhydrous CH3CN a series of nine 4-(4-substituted-benzoyl)-N-methylpyridinium cations (substituent: -OCH3, -CH3, -H, -SCH3, -Br, -C≡CH, -CHO, -NO2, and -+S(CH3)2) demonstrate two chemically reversible, well-separated one-electron (1-e) reductions in the same potential range as other main stream redox catalysts such as quinones and viologens. Hammett linear free energy plots yield excellent correlation between the E1/2 values of both waves and the substituent constants σp-X. The reaction constants for the two 1-e reductions are ρ1 = 2.60 and ρ2 = 3.31. The lower ρ1 value is associated with neutralization of the pyridinium ring, and the higher ρ2 value with the negative charge developing during the 2nd-e reduction. Structure-function correlations point to a purely inductive role for substitution in both 1-e reductions. The case of the 4-(4-nitrobenzoyl)-N-methylpyridinium cation is particularly noteworthy, because the 4-nitrobenzoyl moiety undergoes reduction before the 2nd reduction of the 4-benzoyl-N-methylpyridinium system. Correlation of the third wave of this compound with the 2nd-e reduction of the others yields σp-NO2- = -0.97 ± 0.02, thus placing the -NO2- group among the strongest electron donors. Solvent deuterium isotope effects and maps of the electrostatic potential (via PM3 calculations) as a function of substitution support that 2-e reduced forms develop H-bonding with proton donors (e.g., CH3-OH) via the O-atom. The average number of CH3OH molecules entering the H-bonding association increases with e-donating substituents. H-bonding shifts the 2nd reduction wave closer to the first one. This has important practical implications, because it increases the equilibrium concentration of the 2-e reduced form from disproportionation of the 1-e reduced form.
- Leventis, Nicholas,Rawaswdeh, Abdel-Monem M.,Zhang, Guohui,Elder, Ian A.,Sotiriou-Leventis, Chariklia
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p. 7501 - 7510
(2007/10/03)
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- Diphenylpropionic acids as new AT1 selective angiotensin II antagonists
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The synthesis and pharmacological evaluation of a new series of potent AT1 selective diphenylpropionic acid nonpeptide angiotensin II receptor antagonists are reported. The new compounds were evaluated for in vitro AT1 (rat liver) an
- Almansa, Carmen,Gómez, Luis A.,Cavalcanti, Fernando L.,De Arriba, Alberto F.,Rodríguez, Ricardo,Carceller, Elena,García-Rafanell, Julián,Forn, Javier
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p. 2197 - 2206
(2007/10/03)
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- Therapeutically useful 1-phenyl-2-piperidinoalkanol derivatives
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Compounds of the formula: STR1 wherein R1 is hydrogen, halogen, trifluoromethyl, alkyl, hydroxyl, alkyoxy, benzyloxy, alkanoyloxy, or benzoyloxy, or when R2 is hydroxyl or methoxy in the 4-position and R3 is hydrogen, R1 may also represent hydroxymethyl carbamoyl or alkoxycarbonyl, R2 is hydrogen, halogen, alkyl, hydroxyl, or alkoxy, R3 is hydrogen or alkyl, R4 is alkyl (in which case the compounds are (±)-erythro) or when R3 represents hydrogen, R4 may also be hydrogen, and R5 is hydrogen, halogen, alkyl, alkoxy, or three methoxy groups in the 3-, 4- and 5-positions and pharmaceutically acceptable acid addition salts thereof, with the exclusion of compounds wherein: (a) one of R1 and R2 is in the 4-position and is hydroxyl, alkoxy or benzyloxy, the other is in the 3-position and is hydrogen, hydroxyl, alkoxy or benzyloxy, and R3 and R5 are hydrogen and wherein: (b) R1 is in the 4-position and is halogen, R4 is methyl and R2, R3 and R5 are hydrogen, are useful as medicaments.
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