- 1,3,2-Diazaphospholenes Catalyze the Conjugate Reduction of Substituted Acrylic Acids
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The potent nucleophilicity and remarkably low basicity of 1,3,2-diazaphospholenes (DAPs) is exploited in a catalytic, metal-free 1,4-reduction of free α,β-unsaturated carboxylic acids. Notably, the reduction occurs without a prior deprotonation of the carboxylic acid moiety and hence does not consume an additional hydride equivalent. This highlights the excellent nucleophilic character and low basicity of DAP-hydrides. Functional groups such as Cbz group or alkyl halides which can be problematic with classical transition-metal catalysts are well tolerated in the DAP-catalyzed process. Moreover, the transformation is characterized by a low catalyst loading, mild reaction conditions at ambient temperature as well as fast reaction times and high yields. The proof-of-principle for a catalytic enantioselective version is described.
- Reed, John H.,Cramer, Nicolai
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p. 4262 - 4266
(2020/07/13)
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- METHOD OF MAKING ACRYLIC ACID FROM LACTIC ACID OR LACTIDE USING MOLTEN SALT CATALYSTS
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A method of making acrylic acid in liquid phase by contacting a feed stream containing lactic acid, lactide, or mixtures thereof with a molten salt catalyst comprising a protic ionic liquid (PIL), which contains a bromide anion (Br-), is provided.
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Page/Page column 37; 38; 39; 41
(2018/09/28)
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- Catalytic Bromination of Alkyl sp3C-H Bonds with KBr/Air under Visible Light
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Alkyl sp3C-H bonds of cycloalkanes and functional branch/linear alkanes have been successfully brominated with KBr using air or O2 as an oxidant at room temperature to 40 °C. The reactions are carried out in the presence of catalytic NaNO2 in 37% HCl (aq)/solvent under visible light, combining aerobic oxidations and photochemical radical processes. For various alkane substrates, CF3CH2OH, CHCl3, or CH2Cl2 is employed as an organic solvent, respectively, to enhance the efficiency of bromination.
- Zhao, Mengdi,Lu, Wenjun
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supporting information
p. 5264 - 5267
(2018/09/12)
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- METHODS OF MAKING ACRYLIC ACID FROM LACTIC ACID OR ITS DERIVATIVES IN LIQUID PHASE
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Methods for making acrylic acid, acrylic acid derivatives, or mixtures thereof by contacting a feed stream containing lactic acid, lactic acid derivatives, or mixtures thereof with a molten salt catalyst comprising an ionic liquid (IL) and an acid in liquid phase are provided.
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Page/Page column 66; 67
(2018/02/28)
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- CATALYSTS FOR MAKING ACRYLIC ACID FROM LACTIC ACID OR ITS DERIVATIVES IN LIQUID PHASE
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Catalysts for the dehydration of lactic acid, lactic acid derivatives, or mixtures thereof to acrylic acid, acrylic acid derivatives, or mixtures thereof in liquid phase comprising an ionic liquid (IL) and an acid are provided.
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Page/Page column 66
(2018/02/28)
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- Zwitterionic Hydrobromic Acid Carriers for the Synthesis of 2-Bromopropionic Acid from Lactide
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A convenient and highly efficient way of synthesizing 2-bromopropionic acid (2-BrPA) from lactide is presented. The procedure uses ionic liquids obtained from the addition of HBr to ammonium-based zwitterions as the solvent and bromination agent. The buffered HBr acidity, high polarity, and charge stabilizing character of the ionic liquid (IL) enable the synthesis of 2-BrPA with excellent selectivity. The best results are obtained with an imidazolium-based IL, that is, 1-(4-butanesulfonic acid)-3-methylimidazolium bromide ([MIMBS]Br). The HBr loading and water content of the IL are crucial parameters for the bromination reaction. The formed 2-BrPA product can be selectively isolated by extraction from the IL, and the unconverted substrate remains in the [MIMBS]Br IL for the next run. Successful recycling of the IL over four cycles is demonstrated.
- Kehrer, Matthias,Mehler, Julian,Taccardi, Nicola,Nagengast, Jens,Kadar, Julian,Collias, Dimitris,Dziezok, Peter,Wasserscheid, Peter,Albert, Jakob
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p. 1063 - 1072
(2018/03/01)
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- Catalytic Cracking of Lactide and Poly(Lactic Acid) to Acrylic Acid at Low Temperatures
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Despite being a simple dehydration reaction, the industrially relevant conversion of lactic acid to acrylic acid is particularly challenging. For the first time, the catalytic cracking of lactide and poly(lactic acid) to acrylic acid under mild conditions is reported with up to 58 % yield. This transformation is catalyzed by strong acids in the presence of bromide or chloride salts and proceeds through simple SN2 and elimination reactions.
- Terrade, Frédéric G.,van Krieken, Jan,Verkuijl, Bastiaan J. V.,Bouwman, Elisabeth
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p. 1904 - 1908
(2017/05/16)
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- Preparation methods of tiopronin and zinc complex of tiopronin
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The invention discloses preparation methods of tiopronin and zinc complex of tiopronin and belongs to the technical field of a medicine compound for relieving acute/chronic liver diseases. The technical scheme is characterized in that the formula is shown in the specification. The operation is simple, the cost of raw materials is low, the repeatability of experimental results of a process route is higher, and the production cost can be remarkably reduced.
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Paragraph 0026; 0027
(2017/02/24)
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- Enantioselective construction of tetrasubstituted stereogenic carbons through bronsted base catalyzed michael reactions: α′-hydroxy enones as key enoate equivalent
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Catalytic and asymmetric Michael reactions constitute very powerful tools for the construction of new C-C bonds in synthesis, but most of the reports claiming high selectivity are limited to some specific combinations of nucleophile/electrophile compound types, and only few successful methods deal with the generation of all-carbon quaternary stereocenters. A contribution to solve this gap is presented here based on chiral bifunctional Bronsted base (BB) catalysis and the use of α′-oxy enones as enabling Michael acceptors with ambivalent H-bond acceptor/donor character, a yet unreported design element for bidentate enoate equivalents. It is found that the Michael addition of a range of enolizable carbonyl compounds that have previously demonstrated challenging (i.e., α-substituted 2-oxindoles, cyanoesters, oxazolones, thiazolones, and azlactones) to α′-oxy enones can afford the corresponding tetrasubstituted carbon stereocenters in high diastereo- and enantioselectivity in the presence of standard BB catalysts. Experiments show that the α′-oxy ketone moiety plays a key role in the above realizations, as parallel reactions under identical conditions but using the parent α,β-unsaturated ketones or esters instead proceed sluggish and/or with poor stereoselectivity. A series of trivial chemical manipulations of the ketol moiety in adducts can produce the corresponding carboxy, aldehyde, and ketone compounds under very mild conditions, giving access to a variety of enantioenriched densely functionalized building blocks containing a fully substituted carbon stereocenter. A computational investigation to rationalize the mode of substrate activation and the reaction stereochemistry is also provided, and the proposed models are compared with related systems in the literature.
- Badiola, Eider,Fiser, Bla,Gmez-Bengoa, Enrique,Mielgo, Antonia,Olaizola, Iurre,Urruzuno, Iaki,Garca, Jess M.,Odriozola, Jos M.,Razkin, Jess,Oiarbide, Mikel,Palomo, Claudio
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supporting information
p. 17869 - 17881
(2015/02/19)
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- Synthesis of enantiomerically enriched-bromonitriles from amino acids
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Two methods were investigated for the preparation of six chiral-bromonitriles with different optic purities. The nitrous deamination of amino acids gives-bromoacids, which react with chlorosulfonyl isocyanate followed by triethylamine to afford-bromonitriles with moderate enantiomeric excess. However, the dehydration of corresponding-bromoamids using thionyl chloride gives-bromonitriles with good enantiomeric excess up to 94%. The use of phosphoryl chloride instead of thionyl chloride results in more than 30% racemization as determined by high-performance liquid chromatograpic analysis.
- Tka, Najeh,Kraem, Jamil,Hassine, Bechir Ben
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p. 735 - 743
(2013/01/15)
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- One-step radiosynthesis of 4-nitrophenyl 2-[18F]fluoropropionate ([18F]NFP); Improved preparation of radiolabeled peptides for PET imaging
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The versatile 18F-labeled prosthetic group, 4-nitrophenyl 2-[18F]fluoropropionate ([18F]NFP), was synthesized in a single step in 45 min from 4-nitrophenyl 2-bromopropionate, with a decay corrected radiochemical yield of 26.2% ± 2.2%. Employing this improved synthesis of [18F]NFP, [18F]GalactoRGD - the current 'gold standard' tracer for imaging the expression of αVβ 3 integrin - was prepared with high specific activity in 90 min and 20% decay corrected radiochemical yield from [18F]fluoride. 4-Nitrophenyl 2-[18F]fluoropropionate ([18F]NFP), was synthesized in a single radiochemical step in 45 minutes and 26% d.c. radiochemical yield from 4-nitrophenyl 2-bromopropionate. Employing this improved synthesis of [18F]NFP, [18F]GalactoRGD was prepared with high specific activity in 90 minutes and 20% d.c. radiochemical yield from [18F]fluoride. Copyright
- Haskali, Mohammad B.,Roselt, Peter D.,Karas, John A.,Noonan, Wayne,Wichmann, Christian W.,Katsifis, Andrew,Hicks, Rodney J.,Hutton, Craig A.
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p. 726 - 730
(2014/01/06)
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- π-deficient 2-(arylsulfonyl)ethyl esters as protecting groups for carboxylic acids
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Several π-deficient 2-(arylsulfonyl)ethyl groups have been studied as carboxylic acid protecting groups. The 2-[3,5-bis(trifluoromethyl)phenylsulfonyl]ethyl group is the most easily removed protecting group for acids under mild basic conditions using aqueous NaHCO3.
- Alonso, Diego A.,Nájera, Carmen,Varea, Montserrat
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p. 277 - 287
(2007/10/03)
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- Mesoionic 5-alkyl-1,3-dithiolium-4-thiolates: Synthesis and brine shrimp toxicity
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A series of twelve 1,3-dithiolium-4-thiolate mesoionic compounds were synthesized and characterized. The synthetical approach starting from α-bromoalkanoic acids to obtain the corresponding 2-N-morpholino-dithiocarbamoyl-carboxylic acids that by on-pot reaction with carbon disulfide and acetic anhydride in triethylamine formed not isolate intermediates, 1,3-dithiolium-4-olates. After, the 2-N-morpholino-5-alkyl-1,3-dithiolium-4-thiolates were obtained by retro 1,3-dipolar addition reactions. The alkyl moiety linked to C-5 of heterocyclic ring permitted the increase of the hydrophobic character and this effect was evaluated on Artemia salina lethality. The results indicated a bell-shaped relationship between the number of carbon of side chain in mesoionic derivatives and LD50 in brine shrimp toxicity assays.
- De Almeida, Paulo Afonso,Da Silva, Tania Maria Sarmento,Echevarria, Aurea
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p. 593 - 600
(2007/10/03)
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- N-hdroxy-2-(alkyl, aryl, or heteroaryl, sulfanyl, sulfinyl or sulfonyl)-3-substituted alkyl, aryl or heteroarylamides as matrix metalloproteinase inhibitors
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Matrix metalloproteinases (MMPs) are a group of enzymes that have been implicated in the pathological destruction of connective tissue and basement membranes. These zinc containing endopeptidases consist of several subsets of enzymes including collagenases, stromelysins and gelatinases. TNF-α converting enzyme (TACE), a pro-inflammatory cytokine, catalyzes the formation of TNF-α from membrane bound TNF-α precursor protein. It is expected that small molecule inhibitors of MMPs and TACE therefore have the potential for treating a variety of disease states. The present invention provides low molecular weight, non-peptide inhibitors of matrix metalloproteinases (MMPs) and TNF-α converting enzyme (TACE) for the treatment of arthritis, tumor metastasis, tissue ulceration, abnormal wound healing, periodontal disease, bone disease, diabetes (insulin resistance) and HIV infection having the formula wherein R2and R3form a heterocyclic ring and A is S, S(O), or S(O)2, and R1and R4are defined herein.
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- Bifunctional detection agents having a polymer covalently linked to an MRI agent and an optical dye
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The invention provides bifunctional detection agents comprising optical dyes covalently linked to at least one magnetic resonance image (MRI) contrast agent. These agents may include a linker, which may be either a coupling moiety or a polymer.
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- A simple and efficient method of preparing α-bromo carboxylic acids
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A new and convenient method for α-bromination of aliphatic carboxylic acids is reported. Heating carboxylic acids for 16 hours at 85 °C in trifluoroacetic acid with 1.5 equivalents of N-bromosuccinimide and a catalytic amount of concentrated H2SO4 leads to good yields of the respective α-bromocarboxylic acids.
- Zhang, Lian Hao,Duan, Jianxin,Xu, Yuelian,Dolbier Jr., William R.
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p. 9621 - 9622
(2007/10/03)
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- Preparation of optically active α-(hydroxyphenoxy)alkanecarboxylic acids and derivatives thereof
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Optically active α-(hydroxyphenoxy)-alkanecarboxylic acids or derivatives thereof, for example D-2-(4-hydroxyphenoxy)propionic acid or lower alkyl ester thereof, are prepared by (a) saponifying an alkyl ester of an optically active α-halogeno-alkanecarboxylic acid, in an alcoholic solvent medium, by reacting same with an aqueous solution of an alkali metal hydroxide, thereby providing a solution of an alkali metal salt of an optically active α-halogeno-alkanecarboxylic acid, (b) next reacting the step (a) solution thus provided with a dihydroxybenzene or salt thereof, in the presence of an alkali metal hydroxide and in an alcoholic solvent medium, and thence (c) recovering the optically active α-(hydroxyphenoxy)-alkanecarboxylic acid or derivative thereof from the medium of reaction.
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- Kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates
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The kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates are reported.In acidic media, 18O isotope exchange studies, kinetics, activation parameters and substituent effects point clearly to an AAl-1 mechanism with the formation of an alkoxycarbonium ion as the rate-limiting step.In basic media the data indicate a conventional BAc-2 mechanism through attack of hydroxide ion on the carbonyl carbon.In neutral medium (pH 2.5-8.8) there is a certain amount of conflicting evidence which leads, however, to the proposal that hydrolysis occurs via attack of a water molecule on the acyl carbon as the rate-limiting step.
- Hall, C. Dennis,Goulding, Celia W.
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p. 1471 - 1478
(2007/10/02)
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- Specific esterase activity of subtilisin toward esters of α-haloacids
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Esters of α-haloacids are specific substrates for subtilisin which catalyses their hydrolysis in aqueous media. The same esters undergo transesterifications in organic solvents in the presence of subtilisin immobilized on an alumina-phosphate complex.
- Pugniere,Juan, C. San,Previero
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p. 4883 - 4886
(2007/10/02)
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- Preparation of α-Bromo- and α-Chlorocarboxylic Acids from α-Amino Acids
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Diazotization of α-amino acids in 48:52 (w/w) hydrogen fluoride/pyridine along with excess of potassium halide results in the corresponding α-halocarboxylic acids in good to excellent yields (Table 1 and 2).
- Olah, George A.,Shih, Joseph,Prakash, G. K. Surya
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p. 1028 - 1030
(2007/10/02)
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- MERCURATION OF 2-ALKYL-1,3-DIOXOLAN-2-YLIUM SALTS: NEW METHOD FOR THE SYNTHESIS OF α-MERCURIO CARBOXYLIC ACIDS
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In the mercuration of 2-alkyl-1,3-dioxolan-2-ylium perchlorates with mercury acetate of trifluoroacetate high yileds of mono-, di-, and tri-α-mercurio derivatives of carboxylic acids wre obtained, depenging on the proportions of the reacting substrates.
- Boev, V. I.,Dombrovskii, A. V.
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p. 1927 - 1930
(2007/10/02)
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