- Kinetics and Mechanisms of the Reactions of Ketenes with Water and Alcohols in Dioxane Solutions
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The spontaneous addition of water to diphenyl- and to dimethyl-ketene in dioxane-H2O and dioxane-D2O mixtures is third order in the stoicheiometric water concentration, s, when s H2O/kD2O = 1.7-2.3 for all the systems studied.The addition of ethanol to diphenylketene in dioxane-ethanol mixtures has a kinetic pattern very similar to that for addition of water to this ketene, except that the change to a lower order occurs when s = 5M.The variation of the activation parameters with medium composition is also very similar for all these spontaneous additions: at low water or ethanol concentrations Ea = 1+/- 1 kcal mol-1, and ΔS++ = -60 +/- 8 cal K-1 mol-1; at higher concentrations Ea rises somewhat, and ΔS++ becomes less negative.The results are considered in the light of previous work.It is concluded that water and alcohol add to ketenes by a common mechanism in non-hydroxylic solvents of low dielectric constant, and that this involves a cyclic, hydrogen-bonded transition state such as (1).Hydroxide ions (ca. 5*1E-3M) have no effect on the rate of water addition in dioxane, but hydrogen ions have powerful effects: the addition to diphenylketene is inhibited, that to dimethylketene is catalysed.These observations are explained.The isotope effect kH3O+/kD3O+ = 1.9 for the catalysis.We propose a catalytic mechanism with a cyclic transition state (3) involving a dominant slow proton transfer to the ketene β-carbon atom.
- Poon, Nai L.,Satchell, Derek P.N.
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- A Comparison of the Mechanism of Hydrolysis of Diphenylketene and Dimethylketene in Diethyl Ether Solution
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The spontaneous hydrolysis of diphenylketene in diethyl ether solution at 25 deg C is first order in the ketene concentration and third order in the stoicheiometric water concentration; unlike the hydrolysis of dimethylketene, it is not-auto-catalytic and hydrolysis is negligibly catalised by added carboxylic acids.Added boron trifluoride strongly inhibits the hydrolysis of diphenylketene in ether but powefully catalyses that of dimethylketene; the formation of the strong Broensted acid H2OBF3 (association constant K = 120 +/- 20 l mol-1 at 25 deg C) underlines these effects.A pKa value of ca. 0.5 is deduced for this acid and the results as a whole point to the marked inability of diphenylketene , compared with dimethylketene, to accept protons from Broensted acids.Predominantly nucleophilic attack on the ketene is, however, easier for the diphenyl-derivative whose spontaneous hydrolysis varies between ca. 5- and ca. 40-fold faster over the range of stoicheoimetric water concentrations used.
- Poon, Nai L.,Satchell, Derek P. L.
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- The mechanism of the reaction of diphenylketene with bases in aqueous solution: Nucleophilic attack versus general base catalysis of ketene hydration
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Diphenylketene was generated in aqueous solution by flash photolysis, and rates of its decay accelerated by 30 bases of various structure were determined. The rate constants so obtained did not show the regular dependence on basic strength expected if the bases were serving as general base catalysts assisting the attack of water on the ketene, but they did vary with polarizability and steric bulk of the base in the way expected for direct nucleophilic attack of the base on the carbonyl carbon atom of the ketene. Assignment of a direct nucleophilic role to the bases is supported by the formation of amide products in addition to diphenylacetic acid in the reaction of diphenylketene accelerated by ammonia and morpholine, and quantitative analysis of the product ratios shows that these two bases serve only as nucleophiles and that the diphenylacetic acid is formed by uncatalyzed reaction of diphenylketene with solvent water.
- Andraos,Kresge
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- COBALT-CATALYZED SYNTHESIS OF α-ARYLPROPIONIC AND DIARYLACETIC ACIDS
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The cobalt-catalyzed carbonylation of ArCH(R)X (R=CH3, C6H5; X=Cl, Br) in alcoholic solvents under atmospheric pressure of CO is reported.Selective, high yield synthesis of the corresponding acids ArCH(R)COOH can be achieved within a very narrow range of experimental conditions by controlling kinetically the reversible interconversion of intermediate aryl and alkylcobalt complexes.The important roles of the base and of the alcoholic medium are briefly discussed.
- Francalanci, F.,Gardano, A.,Foa, M.
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- Electrosynthesis of 2-benzhydrylidene-4,4-diphenyl-[1,3]oxathiolan-5-one: The reaction pathway
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The pathway for the electrochemical formation of 2-benzhydrylidene-4,4-diphenyl-[1,3]oxathiolan-5-one (2), in dichloromethane tetraethylammonium bromide on graphite cathode is proposed. It involves reaction between electrogenerated diphenylketene (3), 2-bromo-2,2-diphenylacetyl bromide (1) and sulfide anion. The latter is formed from H2S generated in the anodic compartment and electrogenerated bases.
- Lozano, Jose I.,Barba, Fructuoso
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- Anodic oxidation of benzil hydrazones in the presence of halide ions
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Benzil hydrazones were subjected to electrolytic oxidation in MeOH containing halide ion source, such as KI and KBr. The results show that the reaction products were dependent on both the electrolytes and the substituents. In the presence of KI, benzoylphenyldiazomethanes were obtained, whereas in the presence of KBr, benzil dimethyl acetals were obtained.
- Okimoto, Mitsuhiro,Takahashi, Yukio
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- Synthesis of l -octaarginine through microencapsulated palladium-catalyzed allyl ester deprotection
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Octaarginine has been described as a molecular transporter. We report a useful synthesis of orthogonally protected l-octaarginine by using a method based on a microencapsulated palladium catalyst. Known palladium-based methods for allyl ester deprotection have been modified to facilitate purification of the unprotected intermediates. This improvement in the purification step has also been tested with a variety of allyl α-amino esters and allyl α,β-unsaturated esters.
- Pérez-López, Ana M.,González-Calderón, Dávir,Occorso, Antonio,Galindo-ángel, Javier,Domínguez-Seglar, José F.,Tamayo, Juan A.,Díaz-Gavilán, Mónica,Gómez-Vidal, José A.
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- X-ray crystallographic studies and comparative reactivity studies of a sodium diisopropylamide (NDA) complex and related hindered amides
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Two related sodium amide complexes derived from secondary amines with bulky organic substituents have been synthesised and crystallographically characterised. Both [(iPr)2NNa(TMEDA)]2 and [Cy(iPr)NNa(TMEDA)]2 adopt dimeric crystal structures with a central, planar (nitrogen-metal)2 azametallocycle, a now familiar feature in both lithium amide and sodium amide chemistry. TMEDA ligands chelate in their usual bidentate manner making the Na+ cations four-coordinate with a distorted tetrahedral geometry. In the latter complex, the amido substituents are disposed in a trans conformation with respect to the (NNa)2 ring plane. The deprotonating ability of the former complex has been tested against that of the parent amide [(iPr)2NNa]∞ and the lithium congener [(iPr)2NLi]∞ (LDA) in a series of simple organic reactions: selective enolate formation from 2-octanone and 2-methylcyclohexanone; synthesis of diphenylacetic acid via diphenylmethane. In general, the performance of the sodium reagents compares favourably with that of the lithium reagent.
- Andrews, Philip C.,Barnett, Nicholas D.R.,Mulvey, Robert E.,Clegg, William,O'Neil, Paul A.,Barr, Donald,Cowton, Lucy,Dawson, Andrea J.,Wakefield, Basil J.
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- Bis-Rhodamines Bridged with a Diazoketone Linker: Synthesis, Structure, and Photolysis
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Two fluorophores bound with a short photoreactive bridge are fascinating structures and remained unexplored. To investigate the synthesis and photolysis of such dyes, we linked two rhodamine dyes via a diazoketone bridge (?COCN2?) attached to p
- Belov, Vladimir N.,Bossi, Mariano L.,Hell, Stefan W.,Shojaei, Heydar
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- Relative activity of metal cathodes towards electroorganic coupling of CO2 with benzylic halides
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Electrochemical reduction of benzylic halides represents a convenient route to generating carbanions for their subsequent coupling with CO2 to obtain various carboxylic acids. Despite the industrial prospects of this synthetic process, it still lacks systematic studies of the efficient catalysts and reaction media design. In this work, we performed a detailed analysis of the catalytic activity of a series of different metal electrodes towards electroreduction of benzylic halides to corresponding radicals and carbanions using cyclic voltammetry. Specifically, we screened and summarized the performance of 12 bulk metal cathodes (Ag, Au, Cu, Pd, Pt, Ni, Ti, Zn, Fe, Al, Sn, and Pb) and 3 carbon-based materials (glassy carbon, carbon cloth, and carbon paper) towards electrocarboxylation of eight different benzylic halides and compare it to direct CO2 reduction in acetonitrile. Extensive experimental studies along with a detailed analysis of the results allowed us to map specific electrochemical properties of different metal electrodes, i.e., the potential zones related to the one- and two-electron reduction of organic halides as well as the potential windows where the electrochemical activation of CO2 does not occur. The reported systematic analysis should facilitate the development of nanostructured electrodes based on group 10 and 11 transition metals to further optimize the efficiency of electrocarboxylation of halides bearing specific substituents and make this technology competitive to current synthetic methods for the synthesis of carboxylic acids.
- Engelhardt, Helen,Klinkova, Anna,Medvedev, Jury J.,Medvedeva, Xenia V.
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- Desulfonylative Electrocarboxylation with Carbon Dioxide
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Electrocarboxylation of organic halides is one of the most investigated electrochemical approaches for converting thermodynamically inert carbon dioxide (CO2) into value-added carboxylic acids. By converting organic halides into their sulfone derivatives, we have developed a highly efficient electrochemical desulfonylative carboxylation protocol. Such a strategy takes advantage of CO2as the abundant C1 building block for the facile preparation of multifunctionalized carboxylic acids, including the nonsteroidal anti-inflammatory drug ibuprofen, under mild reaction conditions.
- Zhong, Jun-Song,Yang, Zi-Xin,Ding, Cheng-Lin,Huang, Ya-Feng,Zhao, Yi,Yan, Hong,Ye, Ke-Yin
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supporting information
p. 16162 - 16170
(2021/09/02)
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- Room Temperature Coupling of Aryldiazoacetates with Boronic Acids Enhanced by Blue Light Irradiation
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A visible-light-promoted photochemical protocol is reported for the coupling of aryldiazoacetates with boronic acids. This photochemical reaction shows great enhancement compared to the same protocol performed in the absence of light. Except for a few cases, the room temperature coupling in the dark (thermal process) generally does not work. When it does, it is likely to also involve free carbenes as key intermediates. Alternatively, photochemical reactions show a broad scope, can be performed under air and tolerate a wide variety of functional groups. Reaction-evolution monitoring, DFT calculations and control experiments have been used to evaluate the main aspects of this intricate mechanistic scenario. Biologically active molecules Adiphenine, Benactyzine and Aprophen have been prepared as examples of synthetic applications.
- da Silva, Amanda F.,Afonso, Marco A. S.,Cormanich, Rodrigo A.,Jurberg, Igor D.
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supporting information
p. 5648 - 5653
(2020/04/22)
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- Catalytic C-C coupling of diazo compounds with arylboronic acids: Using surface modified sewage sludge as catalyst
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A green, mild and efficient synthesis of diarylmethines using sewage sludge-derived carbonaceous materials (SW) by perchloric acid catalyzed coupling reactions between diazo compounds and arylboronic acids was developed. The reaction shows a high level of functional tolerance and a broad substrate scope. Furthermore, the highly selective 1,2-alkyl shift products were furnished through the sterically demanding R4, R5 migration of diazo compounds (3-diazochromanone). The structures of 1,2-shift products have been further confirmed by single-crystal X-ray analysis. Significantly, the synthesis of the core structures of darifenacin (a clinical drug for overactive bladder syndrome, OAB) and diclofensine (a stimulant drug showing antidepressant and monoamine reuptake inhibitor activity) further demonstrated the efficacy and synthetic potential of this method. This journal is
- Huang, Fei,Huang, He,Hughes, Timothy,Xie, Yuxing,Xu, Jun,Yu, Yang,Zhang, Zhipeng
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supporting information
p. 4165 - 4173
(2020/07/14)
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- Achiral Derivatives of Hydroxamate AR-42 Potently Inhibit Class i HDAC Enzymes and Cancer Cell Proliferation
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AR-42 is an orally active inhibitor of histone deacetylases (HDACs) in clinical trials for multiple myeloma, leukemia, and lymphoma. It has few hydrogen bond donors and acceptors but is a chiral 2-arylbutyrate and potentially prone to racemization. We report achiral AR-42 analogues incorporating a cycloalkyl group linked via a quaternary carbon atom, with up to 40-fold increased potency against human class I HDACs (e.g., JT86, IC50 0.7 nM, HDAC1), 25-fold increased cytotoxicity against five human cancer cell lines, and up to 70-fold less toxicity in normal human cells. JT86 was ninefold more potent than racAR-42 in promoting accumulation of acetylated histone H4 in MM96L melanoma cells. Molecular modeling and structure-activity relationships support binding to HDAC1 with tetrahydropyran acting as a hydrophobic shield from water at the enzyme surface. Such potent inhibitors of class I HDACs may show benefits in diseases (cancers, parasitic infections, inflammatory conditions) where AR-42 is active.
- Tng, Jiahui,Lim, Junxian,Wu, Kai-Chen,Lucke, Andrew J.,Xu, Weijun,Reid, Robert C.,Fairlie, David P.
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supporting information
p. 5956 - 5971
(2020/06/05)
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- Coordination behaviors of diphenylketene adsorbed in the nanocages of zeolite NaY and AgY
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We investigated in detail how polar cumulene molecules like diphenylketene were accommodated in faujasite zeolite pores based on 13C CP/MAS and DD/MAS NMR analyses as well as quantum chemical calculations after adsorbing the molecule into the zeolite NaY or AgY having “hard” sodium ions or “soft” silver ions. Since the diphenylketene has such a specific structure that a carbonyl group (a hard base) is accumulated by a carbon-carbon double bond (a soft π base), which is conjugated with two benzene rings (soft π bases), it is possible for the diphenylketene to adopt multicoordination modes to different metal ions in the zeolite. Compared with the coordination modes of benzophenone and 1,1-diphenylethene adsorbed in the NaY and AgY, those of diphenylketene were identified, and specific coordination behaviors in the zeolite’s supercages were classified depending on the hard or soft metal characters: The C=O and phenyl coordination modes to Na+ in NaY prevail, while the C=C and phenyl coordination to Ag+ in AgY is favored. We also unveiled the difference in the molecular mobility depending on the types of cations in the zeolite by comparing the 13C CP/MAS and DD/MAS NMR spectra.
- Shibata, Shintaro,Masui, Yoichi,Onaka, Makoto
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supporting information
p. 663 - 670
(2020/12/29)
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- Metal Free, Direct and Selective Deoxygenation of α-Hydroxy Carbonyl Compounds: Access to α,α-Diaryl Carbonyl Compounds
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An efficient, metal free, direct and selective deoxygenation of α-hydroxy carbonyl compounds is achieved with the aid of catalytic amount of aqueous HClO4 (70 %) and triethylsilane as hydride source. A variety of α-hydroxy-α,α-diaryl carbonyl compounds are selectively deoxygenated to give α,α-diaryl carbonyl compounds in good to excellent yields. Intermediacy of α-keto carbenium ion is proposed on the basis of some control experiments and atmospheric pressure chemical ionization mass spectral analysis.
- Kumar, Anil,Sandeep,Venugopalan, Paloth
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- Lithium-Free Synthesis of Sodium 2,2,6,6-Tetramethylpiperidide and Its Synthetic Applications
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Lithium-free synthetic methods for sodium 2,2,6,6-tetramethylpiperide (NaTMP) have been developed using sodium dispersion as a sole sodium source. The prepared NaTMP was used as a Br?nsted base, that exhibited some differences in reactivities from LiTMP. (Figure presented.).
- Asako, Sobi,Kodera, Masato,Nakajima, Hirotaka,Takai, Kazuhiko
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supporting information
p. 3120 - 3123
(2019/05/22)
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- Compound with alpha substituted phenyl structure as well as preparation method and sterilization agent thereof
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The invention relates to the technical field of sterilization and disinfection materials and in particular to a compound with an alpha substituted phenyl structure as well as a preparation method anda sterilization agent thereof. The compound with the alpha substituted phenyl structure, which is provided by the invention, has a sterilization effect by promoting solidification and denaturation ofproteins of pathogenic microorganisms, particularly has a good killing effect on pathogenic bacteria such as escherichia coli, staphylococcus aureus, pseudomonas aeruginosa and bacillus subtilis variants, in addition has no corrosion function on metals, is free of irritant smell, good in water solubility and green and environment-friendly, can be used as an effective component of sterilization agents and are widely applied to various industries.
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Paragraph 0095-0099
(2019/11/12)
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- Electrogenerated Sm(II)-Catalyzed CO2 Activation for Carboxylation of Benzyl Halides
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Sm(II)-catalyzed carboxylation of benzyl halides is reported through the electrochemical reduction of CO2. The transformation proceeds under mild reaction conditions to afford the corresponding phenylacetic acids in good to excellent yields. This user-friendly and operationally simple protocol represents an alternative to traditional strategies, which usually proceeds through the C(sp3)-halide activation pathway.
- Bazzi, Sakna,Schulz, Emmanuelle,Mellah, Mohamed
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supporting information
p. 10033 - 10037
(2019/12/24)
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- Visible-Light-Driven External-Reductant-Free Cross-Electrophile Couplings of Tetraalkyl Ammonium Salts
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Cross-electrophile couplings between two electrophiles are powerful and economic methods to generate C-C bonds in the presence of stoichiometric external reductants. Herein, we report a novel strategy to realize the first external-reductant-free cross-electrophile coupling via visible-light photoredox catalysis. A variety of tetraalkyl ammonium salts, bearing primary, secondary, and tertiary C-N bonds, undergo selective couplings with aldehydes/ketone and CO2. Notably, the in situ generated byproduct, trimethylamine, is efficiently utilized as the electron donor. Moreover, this protocol exhibits mild reaction conditions, low catalyst loading, broad substrate scope, good functional group tolerance, and facile scalability. Mechanistic studies indicate that benzyl radicals and anions might be generated as the key intermediates via photocatalysis, providing a new direction for cross-electrophile couplings.
- Liao, Li-Li,Cao, Guang-Mei,Ye, Jian-Heng,Sun, Guo-Quan,Zhou, Wen-Jun,Gui, Yong-Yuan,Yan, Si-Shun,Shen, Guo,Yu, Da-Gang
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p. 17338 - 17342
(2019/01/04)
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- Ruthenium-catalyzed umpolung carboxylation of hydrazones with CO2
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The first ruthenium-catalyzed umpolung carboxylation of hydrazones with CO2 to generate important aryl acetic acids is reported. Besides aldehyde hydrazones, a variety of ketone hydrazones, which have not been successfully applied in previous umpolung reactions with other reactive electrophiles, also show high reactivity and selectivity under mild conditions. Moreover, this operationally simple protocol features good functional group tolerance, is readily scalable, and offers easy derivation of important structures, including bioactive felbinac and adiphenine. Computational studies reveal that this umpolung reaction proceeds through the generation of a Ru-nitrenoid followed by concerted [4 + 2] cycloaddition with CO2.
- Yan, Si-Shun,Zhu, Lei,Ye, Jian-Heng,Zhang, Zhen,Huang, He,Zeng, Huiying,Li, Chao-Jun,Lan, Yu,Yu, Da-Gang
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p. 4873 - 4878
(2018/06/07)
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- Synthetic method of fatty acid containing nitrogen heterocycle
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The invention discloses a synthetic method of fatty acid containing nitrogen heterocycle. The synthetic method comprises the following steps: (S1) adding a heterocyclic compound with substitution of chloromethyl groups, a catalyst and a solvent DMF into a reaction kettle; (S2) introducing carbon dioxide to lead the pressure in the kettle to be 2-4MPa, adjusting and reacting for 10-16 hours at thetemperature of 40-50 DEG C; (S3) adding diluted hydrochloric acid into the reaction kettle to carry out acidification, using ethyl acetate for extraction, combining organic phases, carrying out rotaryevaporation to remove liquid, and further carrying out vacuum drying, thus obtaining the fatty acid containing nitrogen heterocycle. The synthetic method disclosed by the invention has the beneficialeffects that a one-pot method is adopted, the raw materials are easy to obtain, price is low, aftertreatment of products is also simpler, the universality for a substrate is also very high, and the promotion and application are easy.
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Paragraph 0042
(2018/07/30)
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- Additional nucleophile-free FeCl3-catalyzed green deprotection of 2,4-dimethoxyphenylmethyl-protected alcohols and carboxylic acids
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The deprotection of the methoxyphenylmethyl (MPM) ether and ester derivatives can be generally achieved by the combinatorial use of a catalytic Lewis acid and stoichiometric nucleophile. The deprotections of 2,4-dimethoxyphenylmethyl (DMPM)-protected alcohols and carboxylic acids were found to be effectively catalyzed by iron(III) chloride without any additional nucleophile to form the deprotected mother alcohols and carboxylic acids in excellent yields. Since the present deprotection proceeds via the self-assembling mechanism of the 2,4-DMPM protective group itself to give the hardly-soluble resorcinarene derivative as a precipitate, the rigorous purification process by silica-gel column chromatography was unnecessary and the sufficiently-pure alcohols and carboxylic acids were easily obtained in satisfactory yields after simple filtration.
- Sawama, Yoshinari,Masuda, Masahiro,Honda, Akie,Yokoyama, Hiroki,Park, Kwihwan,Yasukawa, Naoki,Monguchi, Yasunari,Sajiki, Hironao
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p. 778 - 784
(2016/07/16)
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- Cathode made of compacted silver nanoparticles for electrocatalytic carboxylation of 1-phenethyl bromide with CO2
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Silver nanoparticles prepared by the direct reduction of AgNO3 in aqueous solution were compacted into coins and used as the cathode for the electrocatalytic carboxylation of 1-phenethyl bromide with CO2. The influences of the working electrode, charge, current density and temperature were investigated. Under optimized conditions, 98% yield of 2-phenylpropionic acid was obtained. The reaction was performed under very mild conditions and no added catalyst was required in the electrolyte. Yields that varied from moderate to excellent were also achieved with other benzyl bromides. This electrode has good stability and reusability, and the yield and selectivity of 2-phenylpropionic acid could be maintained during reuse for 10 times.
- Yang, Hengpan,Wu, Laxia,Wang, Huan,Lu, Jiaxing
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p. 994 - 998
(2016/07/06)
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- Bridging C?H Activation: Mild and Versatile Cleavage of the 8-Aminoquinoline Directing Group
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8-Aminoquinoline has emerged as one of the most powerful bidentate directing groups in history of C?H activation within the last decade. However, cleavage of its robust amide bond has shown to be challenging in several cases, thus jeopardizing the general synthetic utility of the method. To overcome this limitation, we herein report a simple oxidative deprotection protocol. This transformation rapidly converts the robust amide to a labile imide, allowing subsequent cleavage in a simple one-pot fashion to rapidly access carboxylic acids or amides as final products.
- Berger, Martin,Chauhan, Rajan,Rodrigues, Catarina A. B.,Maulide, Nuno
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supporting information
p. 16805 - 16808
(2016/11/16)
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- Selenium catalyzed oxidation of aldehydes: Green synthesis of carboxylic acids and esters
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The stoichiometric use of hydrogen peroxide in the presence of a selenium-containing catalyst in water is here reported as a new ecofriendly protocol for the synthesis of variously functionalized carboxylic acids and esters. The method affords the desired products in good to excellent yields under very mild conditions starting directly from commercially available aldehydes. Using benzaldehyde as a prototype the gram scale synthesis of benzoic acid is described, in which the aqueous medium and the catalyst could be recycled at last five times while achieving an 87% overall yield.
- Sancineto, Luca,Tidei, Caterina,Bagnoli, Luana,Marini, Francesca,Lenardo, Eder J.,Santi, Claudio
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p. 10496 - 10510
(2015/08/06)
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- Taming of superacids: PVP-triflic acid as an effective solid triflic acid equivalent for Friedel-Crafts hydroxyalkylation and acylation
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The application of poly(4-vinylpyridine) supported trifluoromethanesulfonic acid (PVP-TfOH, 1:10) as a convenient solid superacid catalyst system in Friedel-Crafts reactions is described. In the presence of PVP-TfOH, one pot solvent-free synthesis of a wide variety of diarylacetic acid derivatives was achieved by Friedel-Crafts hydroxyalkylation reaction of glyoxylic acid with arenes under mild conditions. Acylation of both activated and deactivated aromatic compounds with acetyl chloride was also achieved using PVP-TfOH complex under solvent-free conditions at room temperature. As the polymer supported triflic acid was found to be a very efficient and an easy-to-handle solid acid, it can be a useful addition to environmentally more adaptable strong acid catalyst systems.
- Prakash, G.K. Surya,Paknia, Farzaneh,Kulkarni, Aditya,Narayanan, Arjun,Wang, Fang,Rasul, Golam,Mathew, Thomas,Olah, George A.
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p. 102 - 112
(2015/03/04)
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- A high-throughput screening method for determining the substrate scope of nitrilases
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Nitrile compounds are intermediates in the synthesis of pharmaceuticals such as atorvastatin. We have developed a chromogenic reagent to screen for nitrilase activity as an alternative to Nessler's reagent. It produces a semi-quantifiable blue colour and hydrolysis of 38 nitrile substrates by 23 nitrilases as cell-free extracts has been shown. This journal is
- Black, Gary W.,Brown, Nicola L.,Perry, Justin J. B.,Randall, P. David,Turnbull, Graeme,Zhang, Meng
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supporting information
p. 2660 - 2662
(2015/03/05)
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- Visible Light Photorelease of Carboxylic Acids via Charge-Transfer Excitation of N-Methylpyridinium Iodide Esters
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Iodide contrast sensitization to direct irradiation of charge transfer salts incurs carboxylic acid release via visible light absorption. The photochemical reduction of N-methyl-4-pyridinium iodide esters to release carboxylic acids is examined using 1H NMR analysis. Photolysis reactions are carried out under mild, biphasic solvent conditions using a household LED lamp. Carboxylic acid release is reported in high yields, and the viability of this method for synthetic chemistry is demonstrated through a macroscale reaction.
- Kunsberg, David J.,Kipping, Allison H.,Falvey, Daniel E.
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p. 3454 - 3457
(2015/07/28)
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- Ketene reactions with tertiary amines
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Tertiary amines react rapidly and reversibly with arylketenes in acetonitrile forming observable zwitterions, and these undergo amine catalyzed dealkylation forming N,N-disubstituted amides. Reactions of N- methyldialkylamines show a strong preference for methyl group loss by displacement, as predicted by computational studies. Loss of ethyl groups in reactions with triethylamine also occur by displacement, but preferential loss of isopropyl groups in the phenylketene reaction with diisopropylethylamine evidently involves elimination. Quinuclidine rapidly forms long-lived zwitterions with arylketenes, providing a model for catalysis by cinchona and related alkaloids in stereoselective additions to ketenes.
- Allen, Annette D.,Andraos, John,Tidwell, Thomas T.,Vukovic, Sinisa
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p. 679 - 685
(2014/04/03)
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- Ni-catalyzed carboxylation of C(sp2)- and C(sp3)-O bonds with CO2
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In recent years a significant progress has been made for the carboxylation of aryl and benzyl halides with CO2, becoming convenient alternatives to the use of stoichiometric amounts of well-defined metal species. Still, however, most of these processes require the use of pyrophoric and air-sensitive reagents and the current methods are mostly restricted to organic halides. Therefore, the discovery of a mild, operationally simple alternate carboxylation that occurs with a wide substrate scope employing readily available coupling partners will be highly desirable. Herein, we report a new protocol that deals with the development of a synergistic activation of CO2 and a rather challenging activation of inert C(sp2)-O and C(sp3)-O bonds derived from simple and cheap alcohols, a previously unrecognized opportunity in this field. This unprecedented carboxylation event is characterized by its simplicity, mild reaction conditions, remarkable selectivity pattern and an excellent chemoselectivity profile using air-, moisture-insensitive and easy-to-handle nickel precatalysts. Our results render our method a powerful alternative, practicality and novelty aside, to commonly used organic halides as counterparts in carboxylation protocols. Furthermore, this study shows, for the first time, that traceless directing groups allow for the reductive coupling of substrates without extended π-systems, a typical requisite in many C-O bond-cleavage reactions. Taking into consideration the limited knowledge in catalytic carboxylative reductive events, and the prospective impact of providing a new tool for accessing valuable carboxylic acids, we believe this work opens up new vistas and allows new tactics in reductive coupling events.
- Correa, Arkaitz,Leon, Thierry,Martin, Ruben
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supporting information
p. 1062 - 1069
(2014/02/14)
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- Ni-catalyzed direct carboxylation of benzyl halides with CO2
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A novel Ni-catalyzed carboxylation of benzyl halides with CO2 has been developed. The described carboxylation reaction proceeds under mild conditions (atmospheric CO2 pressure) at room temperature. Unlike other routes for similar means, our method does not require well-defined and sensitive organometallic reagents and thus is a user-friendly and operationally simple protocol for assembling phenylacetic acids.
- León, Thierry,Correa, Arkaitz,Martin, Ruben
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supporting information
p. 1221 - 1224
(2013/03/14)
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- Oxidative cleavage of α-aryl aldehydes using iodosylbenzene
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We found that α-aryl aldehydes can be cleaved to chain-shortened carbonyl compounds and formaldehyde by various iodosylbenzene complexes. A mechanistic scheme is presented that accounts for the loss of one carbon atom. Formaldehyde is further oxidized to CO and CO2 under the reaction conditions.
- Havare, Nizam,Plattner, Dietmar A.
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supporting information
p. 5078 - 5081,4
(2020/09/15)
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- Electrochemical oxidation of amides of type Ph2CHCONHAr
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Anodic oxidation of N-aryl-2,2-diphenylacetamides in acetonitrile undergoes three types of bond-cleavage, one between the benzylic carbon and the carbonyl group, the second between a carbonyl and 'N', and the third between the 'N' atom and aryl group. The selectivity of the cleavage and nature of emerged products is highly dependent on the nature of substituent attached to the aryl group. For example, electron-withdrawing groups direct the benzyl-carbonyl bond-breaking whereas electron-donating substituents favor the N-aryl bond cleavage. The type of products obtained involve benzophenone, 2,2-diphenylacetamide, N-(diphenylmethylene)acetamide, N-(diphenylmethyl)acetamide, α-lactam (1-acetyl-3,3-diphenylaziridin-2-one, as a 1:1 complex with 2,4-dinitroaniline) and aniline derivatives.
- Golub, Tatiana,Becker, James Y.
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experimental part
p. 3906 - 3912
(2012/06/04)
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- Unusual behavior in the reactivity of 5-substituted- 1H-tetrazoles in a resistively heated microreactor
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The decomposition of 5-benzhydryl-1H-tetrazole in an N-methyl-2- pyrrolidone/acetic acid/water mixture was investigated under a variety of high-temperature reaction conditions. Employing a sealed Pyrex glass vial and batch microwave conditions at 240 °, the tetrazole is comparatively stable and complete decomposition to diphenylmethane requires more than 8 h. Similar kinetic data were obtained in conductively heated flow devices with either stainless steel or Hastelloy coils in the same temperature region. In contrast, in a flow instrument that utilizes direct electric resistance heating of the reactor coil, tetrazole decomposition was dramatically accelerated with rate constants increased by two orders of magnitude. When 5-benzhydryl-1H-tetrazole was exposed to 220 ° in this type of flow reactor, decomposition to diphenylmethane was complete within 10 min. The mechanism and kinetic parameters of tetrazole decomposition under a variety of reaction conditions were investigated. A number of possible explanations for these highly unusual rate accelerations are presented. In addition, general aspects of reactor degradation, corrosion and contamination effects of importance to continuous flow chemistry are discussed.
- Gutmann, Bernhard,Glasnov, Toma N.,Razzaq, Tahseen,Goessler, Walter,Roberge, Dominique M.,Kappe, C. Oliver
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scheme or table
p. 503 - 517
(2011/06/28)
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- Iodide-catalyzed reductions: Development of a synthesis of phenylacetic acids
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A new convenient and scalable synthesis of phenylacetic acids has been developed via the iodide catalyzed reduction of mandelic acids. The procedure relies on in situ generation of hydroiodic acid from catalytic sodium iodide, employing phosphorus acid as the stoichiometric reductant.
- Milne, Jacqueline E.,Storz, Thomas,Colyer, John T.,Thiel, Oliver R.,Dilmeghani Seran, Mina,Larsen, Robert D.,Murry, Jerry A.
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experimental part
p. 9519 - 9524
(2012/01/06)
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- Rapid chemoselective deprotection of benzyl esters by nickel boride
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Benzyl esters of a variety of acids can be chemoselectively cleaved on treatment with nickel boride in methanol at ambient temperature to give the parent carboxylic acids in high yields. Other protecting functionalities such as methyl, ethyl, tert-butyl, and trityl esters as well as benzyl ethers, tert-butyl ethers, and Nbenzylamides are unaffected under these conditions. Georg Thieme Verlag Stuttgart.
- Khurana, Jitender M.,Arora, Reema
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experimental part
p. 1127 - 1130
(2009/12/03)
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- Benzimidazoline-dimethoxypyrene. An effective promoter system for photoinduced electron transfer promoted reductive transformations of organic compounds
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2-(p-Methoxyphenyl)-1,3-dimethylbenzimidazoline (ADMBI) and 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (HPDMBI) are used as reducing reagents in 1,8-dimethoxypyrene (1,8-DMP) sensitized, photoinduced electron transfer (PET) reactions. This system was effectively used for PET induced, reductive transformations of various organic substrates, including α,β-epoxy ketones, the olefin tethered 2-bromomethyl-l-tetralone, and o-allyloxy-iodobenzene, as well as for the deprotection reactions of dodecyl-2-benzoylbenzoate and N-sulfonylindole. The results of studies show that 1,8-DMP is a more effective sensitizer than the previously used 9-methylcarbazole for deprotection of N-methyl-4-picolinium ester.
- Hasegawa, Eietsu,Hirose, Harumi,Sasaki, Kosuke,Takizawa, Shinya,Seida, Takayuki,Chiba, Naoki
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experimental part
p. 1147 - 1161
(2010/10/20)
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- A novel synthetic route to 2-arylalkanoic acids by a ruthenium-catalyzed chemoselective oxidation of furan rings
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An efficient two-step synthesis of 2-arylalkanoic acids from 1-arylalkanols is described. Firstly, 1-arylalkylfuran derivatives were synthesized in high yields by the metal triflate catalyzed Friedel-Crafts alkylation of 2-methylfuran with 1-arylalkanols without employing anhydrous conditions. The chemoselective oxidation of the furan ring in 1-arylalkylfurans to carboxylic acid was then investigated. In a solvent system of hexane-EtOAc/H2O (1:3:4), the furan ring was selectively oxidized with 7 equivalents of NaIO 4 by using 0.5 mol% RuCl3 as catalyst to give 2-arylalkanoic acids in good yields. The selectivity of ruthenium oxidation was controlled by the solvent ratio of hexane-EtOAc. Georg Thieme Verlag Stuttgart.
- Noji, Masahiro,Sunahara, Haruka,Tsuchiya, Ken-Ichi,Mukai, Toru,Komasaka, Ayako,Ishii, Keitaro
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experimental part
p. 3835 - 3845
(2009/07/04)
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- The epimetallation and carbonation of carbonyl and imino derivatives: Epivanadation route to 2-amino and 2-hydroxy acids
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The feasibility of hydrocarboxylating carbonyl and imino derivatives by the two-step process of epimetallation and carbonation has been demonstrated with the model substrates of 9-fluorenone and 9-fluorenone anil. With lithium vanadium dihydride as the epimetallating agent, such hydrocarboxylation has led to a 75% yield of 9-hydroxy-9-fluorenecarboxylic acid and a 65% yield of 9-(N-phenylamino)-9-fluorenecarboxylic acid, respectively. Some initial success in extending the scope of this reaction to other substrates, such as benzophenone, has been achieved by using other epimetallating agents, like the presumed LiV(CH3)2 and Ti(OPri)2. A brief review of the processes and organic synthetic applications of epimetallation and transfer epimetallation of C-C π-bonds is offered as background.
- Eisch, John J.,Fregene, Paul O.,Gitua, John N.
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p. 4647 - 4653
(2008/03/12)
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- 2-Hydroxy-1,2,2-triphenylethanone as an efficient photolabile protecting group for carboxylic acids
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The synthesis is reported of 2-hydroxy-1,2,2-triphenylethanone esters of carboxylic acids by the reaction between 2-chloro-1,2,2-triphenylethanone and a carboxylic acid in the presence of silver carbonate and silver tetrafluoroborate. Photolysis of the esters occurs rapidly on irradiation with a medium-pressure mercury lamp through quartz or Pyrex to return the carboxylic acid. The side product of the photolysis is benzo[b]phenanthro[9,10-d]furan, formed through a tandem process involving initial generation of 2,3-diphenylbenzofuran, photochemical cyclisation and re-aromatisation by aerial oxidation.
- Ashraf, M. Arfan,Russell, Alexander G.,Wharton, Christopher W.,Snaith, John S.
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p. 586 - 593
(2007/10/03)
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- Photorelease of carboxylic acids, amino acids, and phosphates from N-alkylpicolinium esters using photosensitization by high wavelength laser dyes
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Visible light (>450 nm) is used to efficiently cleave carboxylic acids, amino acids, and phosphates from their N-methyl picolinium esters. Photolysis using pyrromethene dyes PM 546 and PM 597 and also coumarin 6 as photosensitizers effects release of carboxylic acids, N-protected amino acids, and phosphates in quantitative yields. The effective rate of photorelease by the dyes, Φε, was found to be as high as 4500 M-1 cm-1. The photorelease proceeds through photoinduced electron transfer from the dye sensitizers to the N-methyl picolinium group. Fluorescence quenching and laser flash photolysis experiments support the photoinduced electron-transfer mechanism. Copyright
- Sundararajan, Chitra,Falvey, Daniel E.
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p. 8000 - 8001
(2007/10/03)
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- Photolytic release of carboxylic acids using linked donor-acceptor molecules: Direct versus mediated photoinduced electron transfer to N-alkyl-4-picolinium esters
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(Chemical Equation Presented) Efficient photorelease (Φ = 0.7) of carboxylic acids is achieved with a covalenlly linked mediator (benzophenone) protecting group (N-alkyl-4-picolinium ester) molecule. The mechanism involves initial photoreduction of the mediator, followed by rapid electron transfer to the protecting group.
- Sundararajan, Chitra,Falvey, Daniel E.
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p. 2631 - 2634
(2007/10/03)
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- Facile Hydrolysis of Esters with KOH-Methanol at Ambient Temperature
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A simple, rapid, and efficient method is reported for the hydrolysis of a variety of mono-and diesters of aromatic, aliphatic, fatty, and heterocyclic acids with potassium hydroxide in methanol at ambient temperature (～35°C).
- Khurana, Jitender M.,Chauhan, Sushma,Bansal, Geeti
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- Polyethylene glycol mediated reductive decyanation of diphenylacetonitrile moderately enhanced by microwave heating
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An efficient and clean procedure for the preparation of alkyldiphenylmethanes and 4,4-diphenylbutylamines from their corresponding nitriles by using sodium hydroxide-polyethylene glycol reagent system in a domestic microwave oven is described. The products are isolated by simple aqueous work up in excellent yields.
- Bendale,Chowdhury,Khadilkar
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p. 433 - 435
(2007/10/03)
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- An efficient and general method for ester hydrolysis on the surface of silica gel catalyzed by indium triiodide under microwave irradiation
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Carboxylic esters are hydrolyzed to the corresponding carboxylic acids in high yields through a simple microwave assisted operation on the surface of silica gel moistened with few drops of water in presence of indium triiodide.
- Ranu,Dutta,Sarkar
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p. 4167 - 4171
(2007/10/03)
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- Photostimulated reactions of phenylacetic acid dianions with aryl halides. Influence of the metallic cation on the regiochemistry of arylation.
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[reaction: see text]Phenylacetic acid dianions react via what appears to be an S(RN)1 process with aryl halides under photostimulation to afford aryl substitution products 5 and 6. When the counterion is K+, only 4-biphenylacetic acids 5 are obtained. Both alpha- and para-coupling occurs with Na+ to give a mixture of 5 and 6, while exclusive formation of diphenylacetic acids 6 is observed with the dilithio salt of 1.
- Nwokogu,Wong,Greenwood,Wolfe
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p. 2643 - 2646
(2007/10/03)
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- Solvent isotope effect on the hydroxide-ioncatalyzed hydration of ketenes in aqueous solution
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Five ketenes, phenyl(ethyl)ketene, phenyl(methylthio)ketene, diphenylketene, pentafluorophenylketene, and 1-naphthylketene, were generated flash photolytically and solvent isotope effects (H2O vs. D2O) on their hydroxide-ioncatalyzed hydration in aqueous solution were determined. The values obtained are all weakly reverse and closely similar (k(HO)/k(DO) = 0.76-0.97), as expected for these fast, hydroxide-ion-consuming reactions, known to proceed by nucleophilic attack of hydroxide on the ketene carbonyl group. The characteristic magnitude of these isotope effects should prove useful in identifying new examples of this reaction.
- Andraos,Chiang,Eustace,Kresge,Paine,Popik,Sung
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p. 459 - 462
(2007/10/03)
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- N-acyl sulfamic acid esters (or thioesters), N-acyl sulfonamides, and N-sulfonyl carbamic acid esters (or thioesters) as hypercholesterolemic agents
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The present invention is directed to compounds useful for the regulation of cholesterol of Formula I, methods for using them and pharmaceutical compositions thereof, STR1 wherein X and Y are oxygen, sulfur, or (CR'R")n wherein n is 1 to 4; R is hydrogen, alkyl, or benzyl; R1 and R2 are phenyl, substituted phenyl, naphthyl, substituted naphthyl, an aralkyl group, an alkyl chain, adamantyl, or a cycloalkyl group.
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- Electrochemical carboxylation of arylmethyl chlorides catalysed by [Co(salen)] [H2salen = N,N′-bis(salicylidene)ethane-1,2-diamine]
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The electrochemical carboxylation of some arylmethyl chlorides RCl [R = benzyl, 4-methoxybenzyl, 4-(trifluoromethyl)benzyl or diphenylmethyl] catalysed by [Co(salen)] [H2salen = N,N′-bis(salicylidene)-ethane-1,2-diamine] was studied in acetonitrile. Comparable amounts of carboxylic acids and saturated hydrocarbons were obtained when R = PhCH2 or 4-MeOC6H4CH2 whereas carboxylic acids were the main products with R = 4-F3CC6H4CH2 or Ph2CH. Electrogenerated [Co1(salen)]- reacts with RCl to give an organometallic complex, [CoIII(salen)R], with a rate constant which, for all chlorides investigated, is of the order of 105 dm3 mol-1 s-1. The one-electron-reduced complex [CoII(salen)R]- is unstable and its decomposition in the presence of CO2 is the key step of the electrocatalytic process. Different decomposition pathways are considered and their mechanistic implications discussed. In the presence of proton donors [CoII(salen)R]- undergoes rapid hydrolysis to RH and [Co(salen)].
- Isse, Abdirisak Ahmed,Gennaro, Armando,Vianello, Elio
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p. 1613 - 1618
(2007/10/03)
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- Synthesis of α,α-disubstituted acetic acids using low-valent titanium
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Digalogenocarbenes generated using low-valent titanium (LVT) undergo a one-pot cycloaddition to diaryl, aryl alkyl or dialkyl ketones to give α,α-disubstituted acetic acids such as (R,S)-2-arylpropanoic acids.TiI4 proved most effective in this reaction for which the product yield was optimized by use of an excess of reducing agent.
- Garcia, Mariano,Campo, Carmen del,Llama, Emilio F.,Sinisterra, Jose V.
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p. 1771 - 1774
(2007/10/02)
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- Mild hydrolysis or alcoholysis of amides. Ti(IV) catalyzed conversion of primary carboxamides to carboxylic acids or esters
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Reaction of primary amides (e.g., 1a or 6-13) or O-methylhydroxamates (1b and 1c) with a catalytic amount of TiCI4 and one equivalent of aqueous HCI converts these compounds in good yields to carboxylic esters (when an alcohol is used as solvent) or to carboxylic acids (when 9:1 dioxane:H2O is used as solvent). These conversions are chemoselective for primary amides: mono- and dialkyl amides are not affected by the reaction conditions. The hydrolysis conditions described do not compromise the stereochemical integrity of an adjacent chiral center. This is exemplified by the hydrolysis of naproxen amide (34) to naproxen (33) without detectable racemization as determined by chiral HPLC.
- Fisher,Caroon,Stabler,Lundberg,Zaidi,Sorensen,Sparacino,Muchowski
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p. 142 - 145
(2007/10/02)
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