- Access to functionalized quinones via the aromatic oxidation of phenols bearing an alcohol or olefinic function catalyzed by supported iron phthalocyanine
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The controlled oxidation at only one position of compounds with several oxidizable sites, while keeping the other sites intact, has been demonstrated for phenols bearing alcohol or olefinic functional groups. Iron tetrasulfophthalocyanine supported on silica was found to be an efficient catalyst for the preparation of functionalized quinones under mild conditions, with tert-butylhydroperoxide as the oxidant. A novel rapid and mild one-pot procedure for the covalent grafting of iron tetrasulfophthalocyanine onto silica has been developed. The supported catalyst was characterized by chemical analysis, a specific surface study, UV-vis spectroscopy and XPS. A non-radical mechanism for this unusual selective oxidation has been revealed by 18O labelling experiments. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Zalomaeva, Olga V.,Sorokin, Alexander B.
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Read Online
- MgBr2 supported on Fe3O4@SiO2?~?urea nanoparticle: An efficient catalyst for ortho-formylation of phenols and oxidation of benzylic alcohols
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Urea was successfully immobilized on the surface of chloropropyl-modified Fe3O4@SiO2 core–shell magnetic nanoparticles, then supported by MgBr2 and acts as a unique catalyst for oxidation of benzylic alcohols to aldehydes and ketones, and ortho-formylation of phenols to salicylaldehydes. The prepared catalyst was characterized by FT-IR, transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, dispersive X-ray spectroscopy, CHN and TGA. It was found that Fe3O4@SiO2?~?urea/MgBr2 showed higher catalytic activity than homogenous MgBr2, and could be reused several times without significant loss of activity.
- Soleimani, Ebrahim,Yaesoobi, Nadieh,Ghasempour, Hamid Reza
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- Efficient microwave-assisted regioselective one pot direct: Ortho -formylation of phenol derivatives in the presence of nanocrystalline MgO as a solid base catalyst under solvent-free conditions
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In this research, at first nanocrystalline MgO was prepared and then the solvent-free reactions of phenol derivatives with paraformaldehyde in the presence of the obtained nanocrystalline MgO as a new catalyst under microwave irradiation were investigated. In this reaction, ortho-hydroxyaromatic aldehydes were yielded as products. This method seems to be comparable with other reported methods due to its high yield and regioselectivity. The significant features of this method are short reaction times, high yields, and easy and quick isolation of the products.
- Naeimi, Hossein,Zakerzadeh, Elham
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- Platinum(II) complexes with tetradentate schiff bases as ligands: Synthesis, Characterization and detection of DNA interaction by differential pulse voltammetry
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Five sterically hindered platinum(II) complexes with tetradentate schiff bases as ligands, [Pt(L)] (L= N,N'-bisalicylidene-1,2-ethylenediamine (L 1), N,N'-bisalicylidene-1,2-cyclohexanediamine (L2), N,N'-bis(5-hydroxylsalicylidene)-1,2-cyclohexanediamine (L3), N,N'-bisalicylidene-1,2-diphenylethylenediamine (L4) and N,N'-bis(3-tert-butyl-5-methyl-salicylidene)-1,2- diphenylethylenediamine (L5) ) have been synthesized and characterized by IR spectroscopy and elemental analysis. The sterical hindrance of antitumor drug candidates potentially makes them less susceptible to deactivation by sulphur containing proteins and helping to overcome resistance mechanisms. The interaction of these metal complexes with fish sperm single-stranded DNA (ssDNA) was studied electrochemically based on the oxidation signals of guanine and adenine. Differential pulse voltammetry was employed to monitor the DNA interaction in solution by using renewable pencil graphite electrode. The results indicate that ligands with different groups can strongly affect the interaction between [Pt(L)] complexes and ssDNA due to sterical hindrances and complex [Pt(L 1)] has the best interaction with DNA among the five complexes.
- Li, Lijun,Tian, Chao,Wang, Cheng,Wang, Guangyuan,Wang, Lianzeng,Du, Jianlong
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- CoTPP-CATALYZED REARRANGEMENT OF 1.4-ENDOPEROXIDES
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Bicyclic endoperoxides with strained and perturbed diene moiety have been submitted to CoTPP-catalyzed rearrangement.Side reaction, like formation of epoxyenone, has been suppressed and yield of the formation of bisepoxides highly increased.
- Balci, Metin,Suetbeyaz, Yasar
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Read Online
- Preparation method of 2, 5-dihydroxy benzaldehyde
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The invention discloses a preparation method of 2, 5-dihydroxy benzaldehyde, which is used for preparing an important intermediate of a liquid crystal compound, and relates to the technical field of liquid crystals. The preparation method comprises the steps of by taking p-methoxyphenol as a raw material, alkyl nitrile as a solvent, paraformaldehyde as a formylation reagent and magnesium chloride and triethylamine as catalysts, reacting for 2-4 hours, extracting reaction liquid by using an organic solvent, washing with water, drying, and evaporating to remove the solvent to obtain liquid 2-hydroxy-5-methoxybenzaldehyde, and then by using toluene as a solvent, and enabling the obtained 2-hydroxy-5-methoxybenzaldehyde to be subjected to a demethylation reaction under the action of anhydrous aluminum trichloride to obtain 2, 5-dihydroxy benzaldehyde; and reacting for 2-4 hours, washing the reaction liquid with water, extracting with an organic solvent, drying, evaporating to remove the solvent, and crystallizing the solvent. The method has the advantages of cheap and easily available raw materials, simple operation and convenient industrial production.
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Paragraph 0017; 0020-0022; 0025-0026
(2021/07/17)
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- METHOD FOR PRODUCING 2-HYDRAZINOBENZOTHIAZOLE DERIVATIVE
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The present invention provides a novel method for producing a 2-hydrazinobenzothiazole derivative. The present invention also provides a method for producing a compound by using the 2-hydrazinobenzothiazole derivative obtained by the production method, and a composition that contains the compound. The present invention also provides a polymerizable composition that is useful in producing film-shaped polymers and contains the compound obtained by the production method. The invention of the present application provides a method for producing a compound represented by general formula (I-C), the method including a step of reacting a compound represented by general formula (I-B) with a compound represented by general formula (I-A) in the presence of at least one compound selected from the group consisting of metal amides, metal hydrides, metal alkoxides, and organic alkali metals. A compound derived from the compound produced by the production method, and a composition that contains the compound are also provided.
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Paragraph 0130; 0135
(2020/06/15)
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- Bisketene Equivalents as Diels-Alder Dienes
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2,5-Bis(tert-butyldimethylsilyloxy)furans are established as vicinal bisketene equivalents for application as dienes in the Diels-Alder reaction. Cycloaddition with olefinic dienophiles, under exceptionally mild conditions, enables convergent access to highly substituted para-hydroquinones in unprotected form via a one-pot Diels-Alder/ring-opening/tautomerization sequence. The synthesis of para-benzoquinones from acetylenic dienophiles, including benzynes, is also demonstrated, and 2,5-bis(tert-butyldimethylsilyloxy)pyrroles are established as competent dienes for the synthesis of para-iminoquinones. Application in natural product synthesis enables gram-scale access to the neuroprotective agent (±)-indanostatin.
- Dissanayake, Isuru,Hart, Jacob D.,Becroft, Emma C.,Sumby, Christopher J.,Newton, Christopher G.
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supporting information
p. 13328 - 13333
(2020/09/03)
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- Substrate-Induced Dimerization Assembly of Chiral Macrocycle Catalysts toward Cooperative Asymmetric Catalysis
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An artificial system of substrate-induced dimerization assembly of chiral macrocycle catalysts enables a highly cooperative hydrogen-bonding activation network for efficient enantioselective transformation. These macrocycles contain two thiourea and two chiral diamine moieties and dimerize with sulfate to form a sandwich-like assembly. The macrocycles then adopt an extended conformation and reciprocally complement the hydrogen-bonding interaction sites. Inspired by the guest-induced dynamic assembly, these macrocycles catalyze the decarboxylative Mannich reaction of cyclic aldimines containing a sulfamate heading group. The imine substrate can be activated toward nucleophilic attack of β-ketoacid by a cooperative hydrogen-bonding network enabled by sulfamate-induced dimerization assembly of the macrocycle catalysts. Highly efficient (>95 % yield in most cases) and enantioselective (up to 97.5:2.5 er) transformation of a variety of substrates using only 5 mol % macrocycle was achieved.
- Ao, Yu-Fei,Guo, Hao,Meng, Wei,Wang, De-Xian,Wang, Qi-Qiang,Zhang, Lie-Wei,Zhou, Hao
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supporting information
p. 2623 - 2627
(2020/02/04)
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- METHOD FOR PRODUCING ESTER GROUP-CONTAINING COMPOUND
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The present invention provides a novel method for producing an ester group-containing compound and a derivative produced using the compound as a synthetic intermediate. The invention also provides a polymerizable composition containing the compound obtained by the production method and a film-shaped polymer obtained by polymerizing the polymerizable composition. The present invention is a method for producing an ester group-containing compound, the method including a mixing step of mixing a condensing agent, a Bronsted acid, a carboxylic acid, and a phenol or an alcohol to prepare a reaction mixture. The Bronsted acid selected is other than the condensing agent, the carboxylic acid, and the phenol.
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Paragraph 0131
(2019/03/08)
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- Method for producing ester group-containing compound being useful for optical material applications such as optical compensation films
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The present invention provides a novel method for producing an ester group-containing compound and a derivative produced by using the compound as a synthetic intermediate. The present invention also provides a polymerizable composition containing the compound obtained by the production method and a film-shaped polymer obtained by polymerizing the polymerizable composition. The present invention is a method for producing an ester group-containing compound, the method including a mixing step of mixing a condensing agent, a Bronsted acid, carboxylic acid, and phenol or alcohol to prepare a reaction mixture. The Bronsted acid is selected from anything other than the condensing agent, the carboxylic acid, and the phenol.
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Paragraph 0192; 0197
(2019/07/16)
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- Method for producing 2-hydrazinobenzothiazole derivative also providing a polymerizable composition which is useful for producing a film-like polymer
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The present invention provides a novel method for producing a 2-hydrazinobenzothiazole derivative. The present invention also provides a method for producing a compound using the 2-hydrazinobenzothiazole derivative obtained by the production method, and a composition containing the compound. The present invention also provides a polymerizable composition which is useful for producing a film-like polymer and contains the compound obtained by the production method. The present invention provides a method for producing a compound represented by general formula (I-C), which comprises a step for reacting a compound represented by general formula (I-B) and a compound represented by general formula (I-A) in the presence of at least one compound selected from the group consisting of metal amides, metal hydrides, metal alkoxides and organic alkali metals; the present invention also relates to a compound derived from the compound produced by the production method and a composition containing the compound.
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Paragraph 0150; 0151; 0157
(2019/09/04)
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- Preparation method of 2,5-dihydroxybenzaldehyde
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The invention provides a method for synthesizing 2,5-dihydroxybenzaldehyde. The method comprises the following steps: with p-dimethoxybenzene as a raw material, carrying out bromination reaction, Grignard reaction and demethylation reaction to obtain the 2,5-dihydroxybenzaldehyde. The preparation conditions are mild, the process is simple, and the industrial application value is high.
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Paragraph 0013; 0018-0020; 0025-0026
(2019/10/29)
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- POLYMERIZABLE COMPOUND AND OPTICALLY ANISOTROPIC BODY
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The present invention provides a compound represented by the general formula (I), and a polymerizable composition containing the compound. When the polymerizable composition containing the compound represented by the formula (I) is used to form a filmy product, the resulting filmy product exhibits less change over time in phase difference and reverse wavelength dispersion and when the filmy polymer is irradiated with UV light, peeling from a substrate is unlikely to be caused. Further, the invention provides a polymer obtained through polymerization of the polymerizable composition and an optically anisotropic body obtained using the polymer.
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Paragraph 0091; 0094; 0110
(2018/11/21)
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- METHOD FOR PRODUCING POLYMERIZABLE COMPOUND
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The polymerizable compound has a hydrazone moiety. The present invention also provides a polymerizable composition in which discoloration and reduction of aligning property do not easily occur. Furthermore, the present invention provides a polymer obtained by polymerizing a polymerizable composition containing a compound obtained by the production method and an optically anisotropic body using the polymer. The present invention provides a method for producing a polymerizable compound including a step of reacting a compound represented by General Formula (I-B-a) with a compound represented by General Formula (I-B-b) to obtain a compound represented by General Formula (I-C), and provides a composition which contains a compound obtained by this production method.
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Paragraph 0142; 0147
(2019/01/04)
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- Co-immobilization of Laccase and TEMPO in the Compartments of Mesoporous Silica for a Green and One-Pot Cascade Synthesis of Coumarins by Knoevenagel Condensation
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Co-immobilization of bio- and chemocatalysts produces sustainable, recyclable hybrid systems that open new horizons for green cascade approaches in organic synthesis. Here, the co-immobilization of laccase and 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) in mesoporous silica was used for the one-pot aqueous synthesis of 30 coumarin-3-carboxylate derivatives under mild conditions through the condensation of in situ oxidized 2-hydroxybenzyl alcohols and malonate derivatives. A maximum yield was obtained after incubating at pH 6.0 and 45 °C for 24 h. An efficient organic synthesis was catalyzed by the hybrid catalyst in 10 % organic solvent. More than 95 % of the initial activity of the enzyme was preserved after 10 cycles, and no significant catalyst deactivation occurred after 10 runs. This new system efficiently catalyzed the in situ aerobic oxidation of salicyl alcohols, followed by Knoevenagel condensation, which confirmed the possibility of producing efficient hybrid catalysts by co-immobilization of catalytic species in mesoporous materials.
- Mogharabi-Manzari, Mehdi,Amini, Mohsen,Abdollahi, Mohammad,Khoobi, Mehdi,Bagherzadeh, Ghodsieh,Faramarzi, Mohammad Ali
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p. 1542 - 1546
(2018/02/28)
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- POLYMERIZABLE COMPOUND AND OPTICALLY ANISOTROPIC BODY
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In light of requests to reduce or reverse the wavelength dispersion of the birefringence of a phase-retardation film in order to increase the viewing angle of a liquid crystal display, the present invention provides a polymerizable compound that reduces, for example, the likelihood of crystals precipitating in a polymerizable composition including the polymerizable compound and enables the polymerizable composition to have high preservation stability and a polymerizable composition including the polymerizable compound which reduces the likelihood of inconsistencies being formed in a film-like polymer produced by polymerizing the polymerizable composition. Another object of the present invention is to provide a polymer produced by polymerizing the polymerizable composition and an optically anisotropic body including the polymer.
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Paragraph 0140-0154
(2018/02/03)
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- Efficient symmetrical bidentate dioxime ligand-accelerated homogeneous palladium-catalyzed Suzuki-Miyaura coupling reactions of aryl chlorides
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A series of N,O-bidentate ligands were synthesized using the Vilsmeier-Haack reaction and oximation. 2,5-Dihydroxyterephthalaldehyde dioxime (L8) as an efficient N,O-symmetrical bidentate ligand was prepared from hydroquinone. It was studied as a high activity ligand for palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of aryl chlorides with arylboronic acids under mild conditions. The coupling reactions were performed in the presence of PdCl2 as the catalyst, L8 as the ligand, Na2CO3 as the base, PEG-400 as the PTC and in ethanol/water (1?:?1) as an environmentally benign solvent at 85 °C. Plentiful biaryls were obtained by the optimized reaction with good yields at a low palladium loading of 0.20 mol%.
- Song, Jinyi,Zhao, Hongyan,Liu, Yang,Han, Huatao,Li, Zhuofei,Chu, Wenyi,Sun, Zhizhong
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supporting information
p. 372 - 376
(2016/12/30)
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- A Novel Covalent mTOR Inhibitor, DHM25, Shows in Vivo Antitumor Activity against Triple-Negative Breast Cancer Cells
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Constitutive activation of the PI3K/mTOR signaling pathway contributes to carcinogenesis and metastasis in most, if not all, breast cancers. From a chromene backbone reported to inhibit class I PI3K catalytic subunits, several rounds of chemical syntheses led to the generation of a new collection of chromologues that showed enhanced ability to kill PI3K-addicted cancer cells and to inhibit Akt phosphorylation at serine 473, a hallmark of PI3K/mTOR activation. This initial screen uncovered a chromene designated DHM25 that exerted potent antitumor activity against breast tumor cell lines. Strikingly, DHM25 was shown to be a selective and covalent inhibitor of mTOR using biochemical and cellular analyses, modeling, and a large panel of kinase activity assays spanning the human kinome (243 kinases). Finally, in vivo, this novel drug was an efficient inhibitor of growth and metastasis of triple-negative breast cancer cells, paving the way for its clinical application in oncology. (Figure Presented).
- Fouqué, Amélie,Delalande, Olivier,Jean, Mickael,Castellano, Rémy,Josselin, Emmanuelle,Malleter, Marine,Shoji, Kenji F.,Hung, Mac Dinh,Rampanarivo, Hariniaina,Collette, Yves,Van De Weghe, Pierre,Legembre, Patrick
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p. 6559 - 6573
(2015/09/07)
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- Water-soluble monochloroplatinum(II) complexes with amino acid derived Schiff bases as ligands: Synthesis, characterisation and antitumour activity
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A series of water-soluble monochloroplatinum(II) complexes K[PtCl(L)] (L = amino acid derived schiff base) have been synthesised as potential anticancer agents and characterised by 1H NMR, elemental analysis, IR spectroscopy and molar conductivity measurements. These compounds were tested for their DNA interaction ability with salmon sperm DNA and their in vitro anticancer activities have been validated against Hela and A549 cell lines by the CCK-8 assay. Whilst some complexes had better cytotoxic activities against the Hela cell line compared with cisplatin, all the complexes had little cytotoxicity against the A549 cell line compared with cisplatin.
- Li, Li-Jun,Tian, Chao,Wang, Zheng,Wang, Guang-Yuan,Wang, Lian-Zeng,Du, Jian-Long
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experimental part
p. 85 - 89
(2012/05/19)
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- Potassium phosphate catalyzed efficient synthesis of 3-carboxycoumarins
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An efficient and rapid synthesis of 3-carboxycoumarins has been expediently accomplished by a reaction of salicylaldehyde with Meldrum's acid using potassium phosphate as an inexpensive catalyst at ambient temperature.
- Undale, Kedar A.,Gaikwad, Dipak S.,Shaikh, Tarannum S.,Desai, Uday V.,Pore, Dattaprasad M.
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experimental part
p. 1039 - 1042
(2012/10/08)
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- Demethylation of aromatic methyl ethers using ionic liquids under microwave irradiation
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An efficient demethylation reaction for aromatic methyl ethers has been developed. Deprotection reactions give high yields with butylpyridinium bromide under microwave irradiation. Basic and acidic functional groups are tolerated if the reaction is performed under acidic conditions.
- Passiniemi, Mikko,Myllymaeki, Mikko J.,Vuokko, Juha,Koskinen, Ari M.P.
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scheme or table
p. 48 - 52
(2012/04/10)
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- CuI-catalyzed hydroxylation of aryl bromides under the assistance of 5-bromo-2-(1H-imidazol-2-yl)pyridine and related ligands
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A number of substituted 2-pyridin-2-yl-1H-benzoimidazoles and 2-(1H-imidazol-2-yl)pyridines were screened for promoting CuI-catalyzed hydroxylation of aryl bromides, which led to the discovery of the combination of CuI and 5-bromo-2-(1H-imidazol-2-yl)pyridine as an effective catalytic system for this transformation. Both electron-rich and electronic-deficient aryl bromides could be converted into the corresponding substituted phenols in good to excellent yields.
- Jia, Jianhuan,Jiang, Chenglin,Zhang, Xiaojing,Jiang, Yongwen,Ma, Dawei
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supporting information; experimental part
p. 5593 - 5595
(2011/11/06)
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- A simple and practical copper-catalyzed approach to substituted phenols from aryl halides by using water as the solvent
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Water surprise! A simple and practical copper-catalyzed approach to substituted phenols by hydroxylation of aryl halides has been developed by using environmentally benign water as the solvent (see scheme). The method proceeds under mild conditions and is tolerant towards various functional groups in the substrates.
- Yang, Daoshan,Fu, Hua
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supporting information; experimental part
p. 2366 - 2370
(2010/06/15)
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- Photolabile protection of 1,2- and 1,3-diols with salicylaldehyde derivatives
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(Chemical Equation Presented) 1,2- and 1,3-diols, including carbohydrates, can be readily caged as acetals of 5-methoxy- or 5-hydroxysalicylaldehydes. Irradiation of these acetals with 300 nm light results in their efficient (Φ = 0.2-0.3) cleavage, regenerating an aldehyde and a glycol in excellent chemical yield. Photoreactive 5-hydroxysalicylaldehyde acetals can be produced by mild in situ reduction of photostable p-quinone precursors.
- Kostikov, Alexey P.,Popik, Vladimir V.
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scheme or table
p. 5277 - 5280
(2009/06/18)
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- Oxidation of aromatic alcohols in irradiated aqueous suspensions of commercial and home-prepared rutile TiO2: A selectivity study
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The photocatalytic oxidation of benzyl alcohol (BA) and 4-methoxybenzyl alcohol (MBA) has been performed in pure water by using commercial TiO 2 samples (Sigma-Aldrich, Merck, Degussa P25) and rutile TiO 2 prepared from TiCl4 at low temperature. Particular attention has been devoted to the identification of the produced aromatic compounds along with the formed CO2. Oxidation products such as the corresponding aromatic aldehyde and acid, as well as mono- and dihydroxylated aldehydes have been detected. The home-prepared rutile sample showed a marked selectivity towards the formation of the aromatic aldehyde (38 and 60% for BA and MBA, respectively), resulting in a three- to sevenfold improvement relative to commercial samples, with the only byproduct being CO2. This catalyst was found to be the most selective in the formation of aldehyde in water. By using the commercial or the calcined home-prepared samples, many hydroxylated aromatic compounds were detected besides the aldehyde and the acid. This finding points to a higher selectivity performance of the home-prepared rutile relative to the commercial TiO2 samples. Some of the home-prepared samples were also dialysed to check the influence of the presence of Cl-1 species on catalyst reactivity and selectivity. We have attempted to explain the different reaction rate and selectivity observed for MBA and BA.
- Augugliaro, Vincenzo,Caronna, Tullio,Loddo, Vittorio,Marci, Giuseppe,Palmisano, Giovanni,Palmisano, Leonardo,Yurdakal, Sedat
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experimental part
p. 4640 - 4646
(2009/05/08)
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- 2,5-Dihydroxybenzyl and (1,4-dihydroxy-2-naphthyl)methyl, novel reductively armed photocages for the hydroxyl moiety
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(Chemical Equation Presented) Irradiation of alcohols, phenols, and carboxylic acids "caged" with the 2,5-dihydroxybenzyl group or its naphthalene analogue results in the efficient release of the substrate. The initial byproduct of the photoreaction, 4-hydroxyquinone-2-methide, undergoes rapid tautomerization into methyl p-quinone. The UV spectrum of the latter is different from that of the caging chromophore, thus permitting selective irradiation of the starting material in the presence of photochemical products. These photoremovable protecting groups can be armed in situ by the reduction of photochemically inert p-quinone precursors.
- Kostikov, Alexey P.,Popik, Vladimir V.
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p. 9190 - 9194
(2008/03/14)
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- Total synthesis of the quinone epoxide dimer (+)-torreyanic acid: Application of a biomimetic oxidation/electrocyclization/Diels-Alder dimerization cascade
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An asymmetric synthesis of the quinone epoxide dimer (+)-torreyanic acid (48) has been accomplished employing [4 + 2] dimerization of diastereomeric 2H-pyran monomers. Synthesis of the related monomeric natural product (+)-ambuic acid (2) has also been achieved which establishes the biosynthetic relationship between these two natural products. A tartrate-mediated nucleophilic epoxidation involving hydroxyl group direction facilitated the asymmetric synthesis of a key chiral quinone monoepoxide intermediate. Thermolysis experiments have also been conducted on a model dimer based on the torreyanic acid core structure and facile retro Diels-Alder reaction processes and equilibration of diastereomeric 2H-pyrans have been observed. Theoretical calculations of Diels-Alder transition states have been performed to evaluate alternative transition states for Diels-Alder dimerization of 2H-pyran quinone epoxide monomers and provide insight into the stereocontrol elements for these reactions.
- Li, Chaomin,Johnson, Richard P.,Porco Jr., John A.
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p. 5095 - 5106
(2007/10/03)
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- Oxygen-Carbon bond dissociation enthalpies of benzyl phenyl ethers and anisoles. An example of temperature dependent substituent effects
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For some time it has been assumed that the direction and magnitude of the effects of Y-substituents on the Z-X bond dissociation enthalpies (BDE's) in compounds of the general formula 4-YC6H4Z-X could be correlated with the polarity of the Z-X bond undergoing homolysis. Recently we have shown by DFT calculations on 4-YC6H4CH2-X (X = H, F, Cl, Br) that the effects of Y on CH2-X BDE's are small and roughly equal for each X, despite large changes in C-X bond polarity. We then proposed that when Y have significant effects on Z-X BDE's it is due to their stabilization or destabilization of the radical. This proposal has been examined by studying 4-YC6H4O-X BDE's for X = H, CH3, and CH2C6H5 both by theory and experiment. The magnitudes of the effects of Y on O-X BDE's were quantified by Hammett type plots of ΔBDE's vs σ+ (Y). Calculations reveal that changes in O-X BDE's induced by changing Y are large and essentially identical (ρ+ = 6.7-6.9 kcal mol-1) for these three classes of compounds. The calculated ρ+ values are close to those obtained experimentally for X = H at ca. 300 K and for X = CH2C6H5 at ca. 550 K. However, early literature reports of the effects of Y on O-X BDE's for X = CH3 with measurements made at ca. 1000 K gave ρ+ ≈ 3 kcal mol-1. We have confirmed some of these earlier, high-temperature O-CH3 BDE's and propose that at 1000 K, conjugating groups such as -OCH3 are essentially free rotors, and no longer lie mainly in the plane of the aromatic ring. As a consequence, the 298 K DFT-calculated ΔBDE for 4-OCH3-anisole of -6.1 kcal mol-1 decreases to -3.8 kcal mol-1 for free rotation, in agreement with the ca. 1000 K experimental value. In contrast, high-temperature O-CH3 ΔBDE's for three anisoles with strongly hindered substituent rotation are essentially identical to those that would be observed at ambient temperatures. We conclude that substituent effects measured at elevated temperatures may differ substantially from those appropriate for 298 K.
- Pratt,De Heer,Mulder,Ingold
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p. 5518 - 5526
(2007/10/03)
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- Pathway of anthracene modification under simulated solar radiation
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Exposure of polycyclic aromatic hydrocarbons (PAHs) to sunlight results in rapid structural photomodification generally via oxidation reactions. These PAH modification products are in many cases more toxic than their parent compounds. In this study, anthracene (ANT), a rapidly photooxidized PAH, was irradiated with simulated solar radiation (SSR, 100 μmol m-2 s- 1) in aqueous solution to examine the photomodification pathway. The photoproducts formed were identified by HPLC. The ANT product profile after 9 h in SSR was very complex, with more than 20 compounds detected. The photoproducts formed were anthraquinones, benzoic acids, benzaldehydes and phenols showing the process to be oxidative in nature. Some of the anthraquinones were themselves subject to photooxidation, and were thus intermediates in the product pathway. The kinetics of ANT photooxidation revealed a pseudo first-order reaction with a half-life of 2 h under the SSR source used. The kinetics of product formation allowed deduction of a probable photomodification pathway. This study indicates that PAH photooxidation products are likely to exist as complex, dynamically changing mixtures in PAH contaminated aquatic environments.
- Mallakin, Ali,George Dixon,Greenberg, Bruce M.
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p. 1435 - 1441
(2007/10/03)
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- [60]Fullerene Adducts with Improved Electron Acceptor Properties
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The synthesis of C60-based dyads in which the C60 core is covalently attached to a strong electron acceptor moiety such as quinones, TCNQ or DCNQI derivatives, has been carried out by 1,3-dipolar cycloaddition of "in situ" generated azomethyne ylides or nitrile oxides to C60. As expected, the obtained pyrrolidino[3′,4′:1,2][60]fullerenes exhibit reduction potentials of the C60 framework which are cathodically shifted in comparison with the parent C60. In contrast, isoxazolo[4′,5′:1,2][60]-fullerenes show reduction waves for the fullerene core that are anodically shifted in comparison with the parent C60, which indicates that they are remarkably stronger acceptors than C60.The electron acceptor organic addend also undergoes an anodic shift due to the electronic interaction with the C60 moiety. The molecular geometry of pyrrolidinofullerenes has been calculated at the semiempirical PM3 level and reveals a highly distorted geometry for the acceptor moiety in compound 13, and a most stable conformation in which both dicyanomethylene units are far away from the C60 surface.
- Illescas, Beatriz M.,Martin, Nazario
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p. 5986 - 5995
(2007/10/03)
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- Fischer's base as a protecting group: Protection and deprotection of 2- hydroxybenzaldehydes
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The hydroxyl and aldehyde groups of 2-hydroxybenzaldehydes were protected by the reaction with Fischer's base and deprotected by the ozonolysis in methanol at -78°C to give the corresponding 2- hydroxybenzaldehydes in good to high yields. (C) 2000 Elsevier Science Ltd.
- Cho, Young Jin,Lee, Seung Hwan,Bae, Jong Woo,Pyun, Hyung-Jung,Yoon, Cheol Min
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p. 3915 - 3917
(2007/10/03)
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- Process for nucleophilic fluoroalkylation of aldehydes
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Aryl difluoromethyl sulfone adds to alkehydes under phase transfer conditions to give novel substituted alcohols of the general formula wherein R is an aryl, cycloaliphatic, sec- or tert-aliphatic, or heterocyclic group and Ar is an aryl group. The substituted alcohols of formula I are of particular utility as intermediates in the synthesis of a variety of useful end products. For example, the products of formula I may be utilized in desulfonylation reactions, oxidation reactions and fluorination reactions.
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- Desilylation of tert-Butyldimethylsilyl Ethers of Phenols
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Treatment of tert-butyldimethylsilyl ethers of phenols and diphenols with potassium fluoride in the presence of catalytic amounts of hydrobromic acid in dimethylformamide generates the corresponding phenols or diphenols in high yields.
- Sinhababu, Achintya K.,Kawase, Masami,Borchardt, Ronald T.
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p. 710 - 712
(2007/10/02)
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- HYDROXYLATION DU BENZALDEHYDE ET DE CETONES AROMATIQUES PAR LE PEROXYDE D'HYDROGENE EN MILIEU SUPERACIDE
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Benzaldehyde and aromatic ketones are hydroxylated by hydrogen peroxide in SbF5-HF without formation of products arising from Baeyer-Villiger oxidation.
- Gesson, Jean-Pierre,Jacquesy, Jean-Claude,Jouannetaud, Marie-Paule,Morellet, Guy
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p. 3095 - 3098
(2007/10/02)
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- REGIOSELECTIVE METALLATIONS OF (METHOXYMETHOXY)ARENES
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The methoxymethoxy substituent when attached to an aromatic ring functions as a moderately strong ortho-directing group in hydrogen-metal exchenge reactions.In many cases the propensity of the methoxymethoxylated arene toward ring metallations is greatly enhanced with concomitant suppression of undesirable side reactions such as nucleophilic attack and addition of metallating species.Unlike many other ortho-directing groups, the regio-direction of the methoxymethoxy substituent when in conjunction with other weaker directing groups is dependent upon the metallating medium.Thus, by changing the electron donating capacity of the metallating medium it is possible to selectively direct metallation to either of the positions ortho to the methoxymethoxy substituent.
- Ronald, Robert C.,Winkle, Mark R.
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p. 2031 - 2042
(2007/10/02)
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- Selective Reactions between Phenols and Formaldehyde. A Novel Route to Salicylaldehydes
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Treatment of phenols (1) with 2 mol equiv. of paraformaldehyde in aprotic and poorly electron-donating solvents in the presence of selected metal halides coupled with suitable bases produces salicylaldehydes (3) in high yields.The route is highly selective for ortho-formylation and also specific towards monoformylation.The crucial role of added bases is emphasized.
- Casiraghi, Giovanni,Casnati, Giuseppe,Puglia, Giuseppe,Sartori, Giovanni,Terenghi, Giuliana
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p. 1862 - 1865
(2007/10/02)
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- Process for preparing 2-hydroxybenzoic aldehydes
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There is disclosed a catalytic process for preparing, from phenols and formaldehyde 2-hydroxybenzoic aldehydes some of which are new in the art and, more particularly, a high-selectivity process for preparing the aldehydes by direct synthesis from phenols having at least a free ortho position and formaldehyde, in the presence of a catalyst consisting of anhydrous stannous and/or stannic chloride and of an aprotic binder.
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