- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- Unusual transformation of 4-hydroxy/methoxybenzylic alcohols via C[sbnd]C ipso-substitution reaction using proton-exchanged montmorillonite as media
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We present here proton-exchanged montmorillonite-mediated an unusual transformation of 4-hydroxy and 4-methoxybenzylic alcohols to form symmetrical benzylic ethers and diarylmethanes under mild conditions. Nuclear magnetic resonance spectroscopy and density functional theory calculations support a plausible mechanism, which includes a distinctive aromatic C[sbnd]C ipso-substitution reaction with a hydroxymethyl group as the C-based leaving group.
- Chen, Dongyin,Chen, Xuan,Dong, Zezhong,Jiang, Nan,Li, Fei,Yun, Yangfang,Zhou, Yu
-
supporting information
(2020/11/12)
-
- Aryl Boronic Acid Catalysed Dehydrative Substitution of Benzylic Alcohols for C?O Bond Formation
-
A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C?O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid.
- Estopi?á-Durán, Susana,Donnelly, Liam J.,Mclean, Euan B.,Hockin, Bryony M.,Slawin, Alexandra M. Z.,Taylor, James E.
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p. 3950 - 3956
(2019/02/16)
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- A General Catalytic Method for Highly Cost- and Atom-Efficient Nucleophilic Substitutions
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A general formamide-catalyzed protocol for the efficient transformation of alcohols into alkyl chlorides, which is promoted by substoichiometric amounts (down to 34 mol %) of inexpensive trichlorotriazine (TCT), is introduced. This is the first example of a TCT-mediated dihydroxychlorination of an OH-containing substrate (e.g., alcohols and carboxylic acids) in which all three chlorine atoms of TCT are transferred to the starting material. The consequently enhanced atom economy facilitates a significantly improved waste balance (E-factors down to 4), cost efficiency, and scalability (>50 g). Furthermore, the current procedure is distinguished by high levels of functional-group compatibility and stereoselectivity, as only weakly acidic cyanuric acid is released as exclusive byproduct. Finally, a one-pot protocol for the preparation of amines, azides, ethers, and sulfides enabled the synthesis of the drug rivastigmine with twofold SN2 inversion, which demonstrates the high practical value of the presented method.
- Huy, Peter H.,Filbrich, Isabel
-
supporting information
p. 7410 - 7416
(2018/04/30)
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- Iodine-catalyzed transformation of aryl-substituted alcohols under solvent-free and highly concentrated reaction conditions
-
Iodine-catalyzed transformations of alcohols under solvent-free reaction conditions (SFRC) and under highly concentrated reaction conditions (HCRC) in the presence of various solvents were studied in order to gain insight into the behavior of the reaction intermediates under these conditions. Dimerization, dehydration and substitution were the three types of transformations observed with benzylic alcohols. Dimerization and substitution reactions were predominant in the case of primary- and secondary alcohols, whereas dehydration prevailed in the case of tertiary alcohols. The relative reactivity of substituted 1-phenylethanols in I2-catalyzed dimerization under SFRC provided a good Hammett plot ρ+ = -2.8 (r2 = 0.98), suggesting the presence of electron-deficient intermediates with a certain degree of developed charge in the rate-determining step.
- Jereb, Marjan,Vra?i?, Dejan
-
p. 747 - 762
(2018/01/17)
-
- Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid
-
The synthesis of thioethers starting from alcohols and thiols in the presence of amorphous solid acid catalysts is reported. A silica alumina catalyst with a very low content in alumina gave excellent results in terms of both activity and selectivity also under solvent-free conditions. The reaction rate follows the electron density of the carbinol atom in the substrate alcohol and yields up to 99% and can be obtained for a wide range of substrates under mild reaction conditions.
- Santoro, Federica,Mariani, Matteo,Zaccheria, Federica,Psaro, Rinaldo,Ravasio, Nicoletta
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supporting information
p. 2627 - 2635
(2017/01/09)
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- Base-Free Iridium-Catalyzed Hydrogenation of Esters and Lactones
-
Half-sandwich iridium bipyridine complexes catalyze the hydrogenation of esters and lactones under base-free conditions. The reactions proceed with a variety of ester and lactone substrates. Mechanistic studies implicate a pathway involving rate-limiting hydride transfer to the substrate at high pressures of H2 (≥50 bar).
- Brewster, Timothy P.,Rezayee, Nomaan M.,Culakova, Zuzana,Sanford, Melanie S.,Goldberg, Karen I.
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p. 3113 - 3117
(2016/07/06)
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- Sulfated tungstate as hydroxyl group activator for preparation of benzyl, including p-methoxybenzyl ethers of alcohols and phenols
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Sulfated tungstate was found to be an effective heterogeneous and reusable catalyst for hydroxy group activation–mediated preparation of benzylic ethers including p-methoxybenzylic ethers of a wide range of alcohols and phenols under mild reaction conditions.
- Katkar, Kamlesh V.,Veer, Sachin D.,Akamanchi, Krishnacharya G.
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p. 1893 - 1901
(2016/11/25)
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- Moisture-Tolerant Frustrated Lewis Pair Catalyst for Hydrogenation of Aldehydes and Ketones
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In this paper, we report on the development of a bench-stable borane for frustrated Lewis pair catalyzed reduction of aldehydes, ketones, and enones. The deliberate fine-tuning of structural and electronic parameters of Lewis acid component and the choice of Lewis base provided for the first time, a moisture-tolerant FLP catalyst. Related NMR and DFT studies underpinned the unique behavior of this FLP catalyst and gave insight into the catalytic activity of the resulting FLP catalyst.
- Gy?m?re, ádám,Bakos, Mária,F?ldes, Tamás,Pápai, Imre,Domján, Attila,Soós, Tibor
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p. 5366 - 5372
(2015/09/15)
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- Self-Assembly of Disorazole C1 through a One-Pot Alkyne Metathesis Homodimerization Strategy
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Abstract Alkyne metathesis is increasingly explored as a reliable method to close macrocyclic rings, but there are no prior examples of an alkyne-metathesis-based homodimerization approach to natural products. In this approach to the cytotoxic C2-symmetric marine-derived bis(lactone) disorazole C1, a highly convergent, modular strategy is employed featuring cyclization through an ambitious one-pot alkyne cross-metathesis/ring-closing metathesis self-assembly process.
- Ralston, Kevin J.,Ramstadius, H. Clinton,Brewster, Richard C.,Niblock, Helen S.,Hulme, Alison N.
-
supporting information
p. 7086 - 7090
(2015/06/08)
-
- Organohalide-catalyzed dehydrative O-alkylation between alcohols: A facile etherification method for aliphatic ether synthesis
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Organohalides are found to be effective catalysts for dehydrative O-alkylation reactions between alcohols, providing selective, practical, green, and easily scalable homo- and cross-etherification methods for the preparation of useful symmetrical and unsymmetrical aliphatic ethers from the readily available alcohols. Mechanistic studies revealed that organohalides are regenerated as reactive intermediates and recycled to catalyze the reactions.
- Xu, Qing,Xie, Huamei,Chen, Pingliang,Yu, Lei,Chen, Jianhui,Hu, Xingen
-
supporting information
p. 2774 - 2779
(2015/05/27)
-
- Selective catalytic synthesis of unsymmetrical ethers from the dehydrative etherification of two different alcohols
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The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4- catalyzes selective etherification of two different alcohols to form unsymmetrically substituted ethers. The catalytic method exhibits a broad substrate scope while tolerating a range of heteroatom functional groups in forming unsymmetrical ethers, and it is successfully used to directly synthesize a number of highly functionalized chiral nonracemic ethers.
- Kim, Junghwa,Lee, Dong-Hwan,Kalutharage, Nishantha,Yi, Chae S.
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p. 3881 - 3885
(2015/01/16)
-
- Zinc-catalyzed reduction of aldehydes with a hydrosilane leading to symmetric ethers and silyl ethers
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The efficient reductive etherification of aromatic or aliphatic aldehydes using a reducing system that combines Zn(OTf)2 with either TMDS or Et3SiH is described. The present reducing system can also be applied to the hydrosilylation of aromatic aldehydes having either a strong electron-withdrawing group or a pyridine ring.
- Sakai, Norio,Nonomura, Yoshifumi,Ikeda, Reiko,Konakahara, Takeo
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p. 489 - 491
(2013/06/26)
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- The efficiency of the metal catalysts in the nucleophilic substitution of alcohols is dependent on the nucleophile and not on the electrophile
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In this study, we investigate the effect of the electrophiles and the nucleophiles for eight catalysts in the catalytic SN1 type substitution of alcohols with different degree of activation by sulfur-, carbon-, oxygen-, and nitrogen-centered nucleophiles. The catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols and follow the trend of alcohol reactivity. However, when it comes to the nucleophile, the eight catalysts show general and specific variances in the efficiency and selectivity to perform the desired substitution. Interestingly, the selectivity of the alcohols to produce the desired substitution products was found to be independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation. Catalysts based on iron(III), bismuth(III), and gold(III) show higher conversions for S-, C-, and N-centered nucleophiles, and BiIII was the most efficient catalyst in all combinations. Catalysts based on rhenium(I) or rhenium(VII), palladium(II), and lanthanum(III) were the most efficient in performing the nucleophilic substitution on the various alcohols with the O-centered nucleophiles. These catalysts generate the symmetrical ether as a by-product from the reactions of S-, C-, and N-centered nucleophiles as well, resulting in lower chemoselectivity. Who's the boss? In a comprehensive study of catalytic S N1 type direct substitution of alcohols, the catalysts do not show any general variance in efficiency or selectivity with respect to the alcohols but are highly variable with respect to the nucleophiles. The reactivity of the alcohols is independent of the electrophilicity of the generated carbocations but highly dependent on the ease of formation of the cation.
- Biswas, Srijit,Samec, Joseph S. M.
-
supporting information
p. 974 - 981
(2013/08/25)
-
- Total synthesis of virgatolide B
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The first total synthesis of the benzannulated spiroketal virgatolide A is presented. Key features include sp3-sp2 Suzuki coupling of an enantiomerically enriched β-trifluoroboratoamide and an aryl bromide, regioselective intramolecular carboalkoxylation, and a 1,3-anti-selective Mukaiyama aldol reaction followed by global deprotection/cyclization with regioselectivity governed by internal hydrogen bonding.
- Hume, Paul A.,Furkert, Daniel P.,Brimble, Margaret A.
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supporting information
p. 4588 - 4591
(2013/09/24)
-
- Competition of C-H and C-O fragmentation in substituted p-methoxybenzyl ether radical cations generated by photosensitized oxidation
-
Laser and steady-state photolysis, sensitized by 2,4,6-triphenylpyrylium tetrafluoroborate (TPP+BF4-), of 4-methoxybenzyl ethers [4-CH3O-C6H4CH(OR 1)R, 1a: R = H, R1 = CH3; 1b: R = H, R 1 = C(CH3)3; 1c: R = CH3, R 1 = C(CH3)3; 1d: R = 4-CH3O-C 6H4, R1 = CH3] was carried out in CH3CN in the presence of oxygen. In particular, steady-state irradiation of 1a, b and d produced benzylic alcohols (together with a small amount of acetamide for 1a and 1b) and the oxidation carbonyl compounds (esters and ketones); 4-methoxy-α-methylbenzyl alcohol was the only product observed with 1c. Time-resolved investigations of 1c and 1d gave evidence of the intermediate benzylic carbocation, coming from the ether radical cation formed within the laser pulse by an electron transfer process from the ether to the TPP+ excited state. These results suggested that, besides the deprotonation of the benzyl carbon, the cleavage of the C-OR1 bond is also operative in the reaction pathways of the ether radical cation. The comparison of these results with those obtained in the photolysis of 1c with the uncharged 9,10-dicyanoanthracene (DCA) upholds a particular behavior of TPP+BF4-, probably due to the specific electrostatic interactions of BF4- with the radical cation. This is also supported by quantum mechanical calculation results performed at the B3LYP/6-31G(d) level to obtain the charge and spin density distributions of radical cations, free and complexed with BF4 -.
- Carlotti, Benedetta,Del Giacco, Tiziana,Elisei, Fausto
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p. 489 - 499
(2013/07/11)
-
- A Mild PPTS-Catalyzed Acetalization of α,β-Unsaturated Aldehydes: The First Single-Step Protocol towards Benzylic Acetals
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A mild and convenient procedure for the synthesis of highly sensitive benzylic acetals from α,β-unsaturated aldehydes and the corresponding benzylic alcohols is reported. The new method provides a single-step access to these compounds for the first time.
- B?se, Dietrich,Lübcke, Marvin,Pietruszka, J?rg
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p. 729 - 733
(2013/04/10)
-
- The direct reductive amination of electron-deficient amines with aldehydes: The unique reactivity of the Re2O7 catalyst
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An unprecedented direct reductive amination of electron-deficient amines such as Cbz-, Boc-, EtOCO-, Fmoc-, Bz-, ArSO2-, Ar2PO-, etc. protected amines with aldehydes is achieved using the Re2O 7 catalyst and silanes as the hydride source. Excellent regioselective mono-alkylation and chemoselective reductive-amination were observed.
- Das, Braja Gopal,Ghorai, Prasanta
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supporting information; experimental part
p. 8276 - 8278
(2012/09/22)
-
- A very practical and selective method for PMB protection of alcohols
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A very simple, practical and efficient one-step heterogeneous protocol for the PMB protection of alcohols using Amberlyst-15 has been developed. The stability and hazard issues regarding PMBCl and PMBBr are totally avoided by directly using anisyl alcohol for the protection. Alcohols are protected in very good yields. The selective mono-PMB protection of diols as well as di-PMB protection of diols was achieved in good yields, along with the demonstration of recyclability of the catalyst.
- Chavan, Subhash P.,Harale, Kishor R.
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scheme or table
p. 4683 - 4686
(2012/09/05)
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- The reductive etherification of carbonyl compounds using polymethylhydrosiloxane activated by molecular iodine
-
Aldehydes and ketones undergo a smooth reductive etherification by polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding symmetrical ethers in excellent yields. This new reagent system (PMHS/I2) provides a simple and convenient route for the preparation of symmetrical ethers from carbonyl compounds.
- Yadav,Subba Reddy,Shiva Shankar,Swamy
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experimental part
p. 46 - 48
(2010/03/24)
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- A mild method for the protection of alcohols using a para-methoxybenzylthio tetrazole (PMB-ST) under dual acid-base activation
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With a view to expand the repertoire of chemoselective methods applicable to sensitive and multifunctional substrates, the p-methoxybenzylation of alcohols under essentially neutral conditions is reported. This was achieved by the silver triflate (AgOTf) activation of 5-(p-methoxybenzylthio)-1-phenyl-1H-tetrazole (PMB-ST) in the presence of 2,6-di-tert-butyl-4-methylpyridine (DTBMP).
- Kotturi, Santosh R.,Tan, Jason S.,Lear, Martin J.
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scheme or table
p. 5267 - 5269
(2009/12/24)
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- Dual behavior of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions
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The dual behavior phenomenon of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions (SFRCs) is described; the governing factor is the stability of the carbonium ion generated from the alcohol; high concentration reaction conditions (HCRCs) or dilute solutions are much less suitable. In the case of benzylic alcohols, loss of optical activity was noted, whereas alkyl alcohols furnished a product with retention of stereochemistry.
- Jereb, Marjan,Vra?i?, Dejan,Zupan, Marko
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scheme or table
p. 2347 - 2352
(2009/09/06)
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- Preparation of potassium alkoxymethyltrifluoroborates and their cross-coupling with aryl chlorides
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(Chemical Equation Presented) A wide variety of alkoxymethyltrifluoroborate substrates were prepared via SN2 displacement of potassium bromomethyltrifluoroborate with various alkoxides in excellent yields. These alkoxymethyltrifluoroborates were effectively cross-coupled with several aryl chlorides. This method provides a unique dissonant disconnect that allows greater flexibility in the design of new and improved synthetic pathways.
- Molander, Gary A.,Canturk, Belgin
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supporting information; experimental part
p. 2135 - 2138
(2009/05/26)
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- High-efficiency conversion of trimethylsilyl ethers to their corresponding ethers using carbon-based solid acid as a new catalyst in heterogeneous mixtures
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Carbon-based solid acid was used as a new catalyst for conversion of trimethylsilyl ethers to their corresponding ethers in heterogeneous mixtures. The experiments were done moderately at room temperature, and high yields in suitable times were obtained under these conditions. Copyright Taylor & Francis Group, LLC.
- Shokrollahi, Arash,Zali, Abbas,Pouretedal, Hamid Reza
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p. 371 - 375
(2008/04/01)
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- Synthesis of para-methoxybenzyl (PMB) ethers under neutral conditions
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2-(4-Methoxybenzyloxy)-4-methylquinoline reacts with methyl triflate in the presence of alcohols to generate a neutral organic salt that transfers the para-methoxybenzyl (PMB) protecting group onto alcohols in high yield and under mild conditions. The Royal Society of Chemistry.
- Nwoye, Ernest O.,Dudley, Gregory B.
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p. 1436 - 1437
(2008/02/02)
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- A general method for the preparation of ethers using water-resistant solid lewis acids
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(Chemical Equation Presented) This most ethereal of cascades: Water-resistant single isolated Lewis acids within the framework of molecular sieves act as excellent general catalysts for the synthesis of ethers (see scheme). On this basis, an environmentally friendly process has been developed for the preparation of fine chemicals that involves a one-pot Meerwein-Ponndorf-Verley reduction/etherification cascade.
- Corma, Avelino,Renz, Michael
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p. 298 - 300
(2008/02/08)
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- The role of aromatic radical cations and benzylic cations in the 2,4,6-triphenylpyrylium tetrafluoroborate photosensitized oxidation of ring-methoxylated benzyl alcohols in CH2Cl2 solution
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A steady-state and laser flash photolysis (LFP) study of the TPPBF 4-photosensitized oxidation of ring-methoxylated benzyl alcohols has been carried out. Direct evidence on the involvement of intermediate benzyl alcohol radical cations and benzylic cations in these reactions has been provided through LFP experiments. The reactions lead to the formation of products (benzaldehydes, dibenzyl ethers, and diphenylmethanes) whose amounts and distributions are influenced by the number and relative position of the methoxy substituents. This behavior has been rationalized in terms of the interplay between the stabilities of benzyl alcohol radical cations and benzyl cations involved in these processes. A general mechanism for the TPPBF 4-photosensitized reactions of ring-methoxylated benzyl alcohols has been proposed, where the a-OH group of the parent substrate acts as the deprotonating base promoting α-C-H deprotonation of the benzyl alcohol radical cation (formed after electron transfer from the benzyl alcohol to TPP*) to give a benzyl radical and a protonated benzyl alcohol, precursor of the benzylic cation. This hypothesis is in contrast with previous studies, where formation of the benzyl cation was suggested to occur from the neutral benzyl alcohol through the Lewis acid action of excited TPP+ (TPP*).
- Branchi, Barbara,Bietti, Massimo,Ercolani, Gianfranco,Angeles Izquierdo,Miranda, Miguel A.,Stella, Lorenzo
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p. 8874 - 8885
(2007/10/03)
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- Efficient methods for the preparation of alkyl-aryl and symmetrical or unsymmetrical dialkyl ethers between alcohols and phenols or two alcohols by oxidation-reduction condensation
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Oxidation-reduction condensation via alkoxydiphenylphosphines (diphenylphosphinite esters) (1), generated in situ from chlorodiphenylphosphine (2) and alcohols, 2,6-dimethyl-1,4-benzoquinone (3), and phenols proceeds smoothly to afford alkyl-aryl ethers in good to high yields under neutral conditions. In a similar fashion, a new and efficient method for the preparation of symmetrical or unsymmetrical dialkyl ethers in good to high yields is established via tetrafluoro-1,4-benzoquinone (fluoranil) (4), alcohols, and 1 formed in situ from nBuLi-treated alcohols and 2. This method is applicable also to the etherification of chiral secondary or tertiary alcohols with retention or inversion of configurations. The inverted ethers are afforded by treating chiral alkoxydiphenylphosphines and achiral alcohols, while the reaction of achiral alkoxydiphenylphosphines and chiral alcohols forms retained ethers.
- Shintou, Taichi,Mukaiyama, Teruaki
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p. 7359 - 7367
(2007/10/03)
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- 4-CYANO-4-DEFORMYLSORDARIN DERIVATIVES
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4-Cyano-4-deformylsordarin derivatives are antifungal agents useful in the treatment and/or prevention of human and animal fungal infections, as well as in the control of phytopathogenic fungi in crops.
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- 4-CYANO-4-DEFORMYLSORDARICIN DERIVATIVES
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4-Cyano-4-deformylsordaricin derivatives are antifungal agents useful in the treatment and/or prevention of human and animal fungal infections, as well as in the control of phytopathogenic fungi in crops.
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- Electrostatic catalysis by ionic aggregates: Scope and limitations of Mg(ClO4)2 as acylation catalyst
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Alkali and alkaline earth metal perchlorates exhibit electrostatic catalysis in the activation of anhydrides for the acylation reaction. Perchlorates with higher values of the charge-size function of the metal ion exhibit better catalytic activity following the order Mg(ClO4) 2>Ba(ClO4)2>LiClO4. Acylation of structurally diverse phenols, thiols, alcohols, and amines have been carried out with stoichiometric amounts of anhydride at room temperature under solvent free conditions in the presence of catalytic amount of Mg(ClO4) 2. Sterically hindered and electron deficient phenols are efficiently acylated. Acylation with sterically hindered anhydrides such as iso-butyric, pivalic, and benzoic anhydrides are carried out with phenols and alcohols in excellent yields. Acid-sensitive alcohols are acylated in excellent yields without any competitive side reactions.
- Chakraborti, Asit K.,Sharma, Lalima,Gulhane, Rajesh,Shivani
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p. 7661 - 7668
(2007/10/03)
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- Silica Sulfuric Acid: An Efficient Catalyst for the Direct Conversion of Primary and Secondary Trimethylsilyl Ethers to their Corresponding Ethers under Mild and Heterogeneous Conditions
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Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence silica sulfuric acid with good to excellent yields under mild and heterogeneous conditions.
- Zolfigol, Mohammad Ali,Mohammadpoor-Baltork, Iraj,Mirjalili, Bibi Fatemeh,Bamoniri, Abdolhamid
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p. 1877 - 1879
(2007/10/03)
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- The use of Nafion-H as an efficient catalyst for the direct conversion of primary and secondary trimethylsilyl ethers to their corresponding ethers under mild and heterogeneous conditions
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Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence Nafion-H with good to excellent yields under mild and heterogeneous conditions.
- Zolfigol, Mohammad Ali,Mohammadpoor-Baltork, Iraj,Habibi, Davood,Mirjalili, BiBi Fatemeh,Bamoniri, Abdolhamid
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p. 8165 - 8167
(2007/10/03)
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- 4-cyano-4-deformylsordaricin derivatives
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4-Cyano-4-deformylsordaricin derivatives are antifungal agents useful in the treatment and/or prevention of human and animal fungal infections, as well as in the control of phytopathogenic fungi in crops.
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-
- Organic reactions catalyzed by methylrhenium trioxide: Dehydration, amination, and disproportionation of alcohols
-
Methylrhenium trioxide (MTO) is the first transition metal complex in trace quantity to catalyze the direct formation of ethers from alcohols. The reactions are independent of the solvents used: benzene, toluene, dichloromethane, chloroform, acetone, and in the alcohols themselves. Aromatic alcohols gave better yields than aliphatic. Reactions between two different alcohols could also be used to prepare unsymmetric ethers, the best yields being obtained when one of the alcohols is aromatic. MTO also catalyzes the dehydration of alcohols to form olefins at room temperature, aromatic alcohols proceeding in better yield. When primary (secondary) amines were used as the limiting reagent, direct amination of alcohols catalyzed by MTO gave good yields of the expected secondary (tertiary) amines at room temperature. Disproportionation of alcohols to alkanes and carbonyl compounds was also observed for aromatic alcohols in the presence of MTO. On the basis of the results of this investigation and a comparison with the interaction between MTO and water, a concerted process and a mechanism involving carbocation intermediates have been suggested.
- Zhu, Zuolin,Espenson, James H.
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p. 324 - 328
(2007/10/03)
-
- Halichondrins and related compounds
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Novel chemical compounds that can be used to synthesize halichondrin B and norhalichondrin B, and related derivatives. The total synthesis of halichondrin B and norhalichondrin B is also disclosed.
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- Phenacylpyridiniothiocephalosporins
-
An antibacterial 3-vic-dihydroxyaroylmethylpyridiniothiomethyl cephalosporin (I) and its salts represented by the following formula: STR1 (wherein, R1 is amino group or acylamino; R2 is hydrogen or methoxy; R3 is hydrogen atom or substituent; R4 is vic-dihydroxyaryl; R5 is straight or branched lower alkylene; R6 is hydrogen, a carboxy-protecting group or combined with Y a negative charge; X is --O--, --S-- or sulfinyl; and Y is a counter-ion of pyridinio or combined with R6 a negative charge), a disinfecting and treating method of bacterial infection using it, and synthetic methods thereof are provided.
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-
-
- Piperaziniocephalosporins
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Antibacterial hydroxyarylpiperazinocephalosporins of the formula: STR1 wherein R1 is amino or acylamino; R2 is H or methoxy; R3 is alkyl; R4 is --(P--C--Q)n --, where P and Q each are H, alkyl or OH, or P and Q combine to form oxo, and n is 0 or 4; R5 is substituted or unsubstituted hydroxyaryl; R6 has a negative charge and is COO, or an anion in combination with an optionally protected carboxy; and X is O, S or S→O; an antibacterial preparation containing the same; a method for killing bacteria and preventing or treating bacterial infection by using the same; and syntheses of the cephalosporins are provided.
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-
- Reduction of carbonyl compounds promoted by silicon hydrides under the influence of trimethylsilyl-based reagents
-
The synthetic utility of hydrosilanes under the influence of trimethylsilyl-based reagents as new reducing systems is described. 1,1,3,3-Tetramethyldisiloxane (TMDS) reagent in combination with iodotrimethylsilane or bromotrimethylsilane produces alkyl halides from aldehydes in good to excellent yields.Polymethylhydrosiloxane (PMS) in the presence of iodotrimethylsilane also produces benzyl iodides in excellent yields.On the contrary, PMS reagent was found unsuitable for the synthesis of benzyl bromides.Similary, TMDS reagent in combination with trimethylsilyl triflate produces symmetrical ethers from aldehydes without concomitant formation of competitive products.Under similar conditions, PMS reagent failed to provide the expected symmetrical ethers and Friedel-Crafts products were formed.Reduction of quinones to hydroquinones is also described.
- Aizpurua, Jesus M.,Lecea, Begona,Palomo, Claudio
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p. 2342 - 2347
(2007/10/02)
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- PHOTOCHEMICAL REACTION OF ALCOHOLS - II. IRRADIATION OF AROMATIC ALCOHOLS
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The UV irradiation of aromatic alcohols leads to the formation of several products: carbonyl compounds, ethers, α-glycols and tetra-aryl-1,4-dioxanes.The photoformation of α-glycols is qualitatively and quantitatively compared to the photoreduction of the carbonyl compounds.It is noteworthy that the glycols are formed with a stereochemistry very different depending upon whether the substrate is an alcohol or a carbonyl compound.The structure, configuration and conformation of the 1,4-dioxanes obtained are studied as well as their origin.Other aspects of the photochemistry of the alcohols are analyzed using hydroperoxides as model substrates.
- Balsells, R. Erra,Frasca, A. R.
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p. 2525 - 2538
(2007/10/02)
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- Synthesis of aryl ethers of bis(hydroxymethyl) ether
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Process for preparing mono- and diaryl ethers of bis(hydroxymethyl) ether by reaction of the dialkyl esters of polyoxymethylene glycols with phenol or substituted phenol. In a preferred embodiment the reaction is carried out in the presence of a catalyst.
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