- Palladium-Catalyzed Highly Regioselective Hydrocarboxylation of Alkynes with Carbon Dioxide
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A Pd-catalyzed highly regioselective hydrocarboxylation of alkynes with carbon dioxide has been established. By the combination of Pd(PPh3)4 and 2,2′-bis(diphenylphosphino)-1,1′-binaphthalene (binap), a variety of functionalized alkynes, including aryl alkynes, aliphatic alkynes, propargylamines, and propargyl ethers, could be leveraged to provide a wide array of α-acrylic acids in high yields with high regioselectivity under mild reaction conditions. Experimental and DFT mechanistic studies revealed that this reaction proceeded via the cyclopalladation process of alkynes and carbon dioxide in the presence of binap to generate a five-membered palladalactone intermediate and enabled the formation of Markovnikov adducts. Moreover, this strategy provided an effective method for the late-stage functionalization of alkyne-containing complicated molecules, including natural products and pharmaceuticals.
- Chen, Pengquan,Cheng, Ruixiang,Jiang, Huanfeng,Lei, Ming,Lou, Hongming,Qi, Chaorong,Shi, Fuxing,Wang, Lu,Wu, Wanqing,Xiong, Wenfang,Zhu, Baiyao
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p. 7968 - 7978
(2020/08/21)
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- Cobalt-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carboxylic Acids by Homolytic H2 Cleavage
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The asymmetric hydrogenation of α,β-unsaturated carboxylic acids using readily prepared bis(phosphine) cobalt(0) 1,5-cyclooctadiene precatalysts is described. Di-, tri-, and tetra-substituted acrylic acid derivatives with various substitution patterns as well as dehydro-α-amino acid derivatives were hydrogenated with high yields and enantioselectivities, affording chiral carboxylic acids including Naproxen, (S)-Flurbiprofen, and a d-DOPA precursor. Turnover numbers of up to 200 were routinely obtained. Compatibility with common organic functional groups was observed with the reduced cobalt(0) precatalysts, and protic solvents such as methanol and isopropanol were identified as optimal. A series of bis(phosphine) cobalt(II) bis(pivalate) complexes, which bear structural similarity to state-of-the-art ruthenium(II) catalysts, were synthesized, characterized, and proved catalytically competent. X-band EPR experiments revealed bis(phosphine)cobalt(II) bis(carboxylate)s were generated in catalytic reactions and were identified as catalyst resting states. Isolation and characterization of a cobalt(II)-substrate complex from a stoichiometric reaction suggests that alkene insertion into the cobalt hydride occurred in the presence of free carboxylic acid, producing the same alkane enantiomer as that from the catalytic reaction. Deuterium labeling studies established homolytic H2 (or D2) activation by Co(0) and cis addition of H2 (or D2) across alkene double bonds, reminiscent of rhodium(I) catalysts but distinct from ruthenium(II) and nickel(II) carboxylates that operate by heterolytic H2 cleavage pathways.
- Chirik, Paul J.,Shevlin, Michael,Zhong, Hongyu
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supporting information
(2020/03/13)
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- Structural insights into the ene-reductase synthesis of profens
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Reduction of double bonds of α,β-unsaturated carboxylic acids and esters by ene-reductases remains challenging and it typically requires activation by a second electron-withdrawing moiety, such as a halide or second carboxylate group. We showed that profen precursors, 2-arylpropenoic acids and their esters, were efficiently reduced by Old Yellow Enzymes (OYEs). The XenA and GYE enzymes showed activity towards acids, while a wider range of enzymes were active towards the equivalent methyl esters. Comparative co-crystal structural analysis of profen-bound OYEs highlighted key interactions important in determining substrate binding in a catalytically active conformation. The general utility of ene reductases for the synthesis of (R)-profens was established and this work will now drive future mutagenesis studies to screen for the production of pharmaceutically-active (S)-profens.
- Waller,Toogood,Karuppiah,Rattray,Mansell,Leys,Gardiner,Fryszkowska,Ahmed,Bandichhor,Reddy,Scrutton
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p. 4440 - 4448
(2017/07/10)
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- Asymmetric Hydrogenation of α-Substituted Acrylic Acids Catalyzed by a Ruthenocenyl Phosphino-oxazoline-Ruthenium Complex
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Asymmetric hydrogenation of various α-substituted acrylic acids was carried out using RuPHOX-Ru as a chiral catalyst under 5 bar H2, affording the corresponding chiral α-substituted propanic acids in up to 99% yield and 99.9% ee. The reaction could be performed on a gram-scale with a relatively low catalyst loading (up to 5000 S/C), and the resulting product (97%, 99.3% ee) can be used as a key intermediate to construct bioactive chiral molecules. The asymmetric protocol was successfully applied to an asymmetric synthesis of dihydroartemisinic acid, a key intermediate required for the industrial synthesis of the antimalarial drug artemisinin.
- Li, Jing,Shen, Jiefeng,Xia, Chao,Wang, Yanzhao,Liu, Delong,Zhang, Wanbin
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p. 2122 - 2125
(2016/06/01)
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- Cs2CO3-promoted carboxylation of N-tosylhydrazones with carbon dioxide toward α-arylacrylic acids
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A Cs2CO3-promoted carboxylation of N-tosylhydrazones and CO2 has been developed. The reaction proceeded efficiently at 80 C under atmospheric CO2, gave the corresponding α-arylacrylic acids in moderate to good yields. This method was featured with (1) the employment of Cs2CO3 rather than nBuLi as the base; (2) a reaction temperature of 80 C rather than -78 C.
- Sun, Song,Yu, Jin-Tao,Jiang, Yan,Cheng, Jiang
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p. 2855 - 2860
(2015/03/18)
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- Enantioselective enolate protonation in sulfamichael addition to r-substituted n-acryloyloxazolidin-2-ones with bifunctional organocatalyst
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Organocatalytic conjugate addition of thiols to R-substituted N-acryloyloxazolidin-2-ones followed by asymmetric protonation has been studied in the presence of cinchona alkaloid derived thioureas. Both of the enantiomers are accessible with the same level of enantioselectivity using pseudoenantiomeric quinine/quinidine derived catalysts. The addition/protonation products have been converted to useful biologically active molecules. 2011 American Chemical Society.
- Rana, Nirmal K.,Singh, Vinod K.
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p. 6520 - 6523
(2012/02/01)
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- On the enzymatic hydrolysis of methyl 2-fluoro-2-arylpropionates by lipases
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The enzymatic hydrolysis of methyl 2-fluoro-2-arylpropionates was performed using lipases from Candida rugosa and Candida cylindracea (OF-360). A careful analysis of the reaction products revealed that racemic 2-hydroxy-2- arylpropionic acid and traces of 2-arylacrylic acid are formed, in addition to the expected 2-aryl-2-fluoropropionic acid. The presence of powerful electron-releasing groups in the aromatic ring of the substrate increase the amount of 2-hydroxypropionic acid. A mechanistic hypothesis has been formulated according to which the enzyme facilitates the elimination of fluoride ion from the hydrolysed acid with the formation of an α-carboxy-stabilized carbocation which provides 2-hydroxypropionic acids by nucleophilic attack of H2O and 2-arylacrylic acids by a β-elimination process.
- Bellezza, Francesca,Cipiciani, Antonio,Ricci, Giacomo,Ruzziconi, Renzo
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p. 8005 - 8012
(2007/10/03)
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- A convenient new synthesis of a Naproxen precursor
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A precursor of Naproxen, 2-(6-methoxy-2-naphthyl)propenoic acid was synthesized in good yield from commercially available 6-methoxy-2-naphthaldehyde in three steps. The synthesis includes an unprecedented one-step reduction of acrylic acid ethyl ester to propenoic acid ethyl ester in high yield.
- Mahmood, Syed J.,Brennan, Courtney,Mahmun Hossain
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p. 1807 - 1809
(2007/10/03)
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- A convenient synthesis of 2-(6-methoxy-2-naphthyl)propenoic acid (a naproxen precursor)
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The title compound has been synthesised via the quantitative hydrocabonylation of the corresponding 1-alkyne in the presence of a palladium catalyst. The reaction proceeds at best under 30 bar of CO, but for the purposes of a laboratory scale synthesis it can be carried out successfully even at atmospheric pressure.
- Scrivanti,Matteoli
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p. 9015 - 9018
(2007/10/02)
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- Method for preparing α-arylpropionic acids
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Process for preparing α-arylpropionic acids by catalytically asymmetrically hydrogenating α-arylpropenoic acids prepared from α-aryl ketones.
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- Asymmetric catalytic hydrogenation of α-arylpropenoic acids
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Process for preparing α-arylpropionic acids by catalytically asymmetrically hydrogenating α-arylpropenoic acids utilizing an asymmetric hydrogenation catalyst at low temperatures and, optionally, at high pressures.
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- Asymmetric catalytic hydrogenation of α-arylpropenic acids
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Process for preparing α-arylpropionic acids by catalytically asymmetrically hydrogenating α-arylpropenoic acids utilizing an asymmetric hydrogenation catalyst at low temperatures and, optionally, at high pressures.
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- A facile, practical synthesis of 2-(6-methoxy-2-naphthyl)propenoic acid
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A facile and practical method for the synthesis of 2-(6-methoxy-2-naphthyl)propenoic acid, a precursor of anti-inflammatory agent naproxen, is described. The method involves (1) Pd-catalyzed ethynylation of 2-bromo-6-methoxynaphthalene, (2) regioselective addition of HX to the triple bond, and (3) Pd-catalyzed carbonylation of the resulting vinyl halide followed by (4) alkaline hydrolysis.
- Hiyama,Wakasa,Ueda,Kusumoto
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p. 640 - 642
(2007/10/02)
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- ASYMMETRIC HYDROGENATION OF α-ARYLPROPENOIC ACIDS CATALYZED BY RHODIUM(I) COMPLEXES OF CHIRAL LIGANDS DERIVED FROM SOME MONOSACCHARIDES
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Prochiral precursors, 3 and 6, of (+)-Ketoprofen, 1, and (+)-Naproxen, 2, are hydrogenated in the presence of various Rh(I) complexes of chiral diphenylphosphines and diphenylphosphinites (15-21).The last four ligands (18-21) are derived from the most widespread monosaccharides, D-glucose, D-xylose, D-galactose and L-arabinose.The optical yields (e.e.s. in percent) varied from low to medium (ca. 10-50percent), indicating that none of the substrates 3 and 6 behave as bidentate ligand within any of the examined catalytic species.The highest e.e. (45percent) was obtained with 6, using the Rh(I) complex of 20 as catalyst.No "double asymmetric induction" either intramolecular (in 8) or intermolecular (in 13) has been reached when hydrogenation with 21 was tried; diastereomeric excess (d.e.) (ca. 25percent) only approaches the e.e.s. obtained for prochiral substrates 3 and 6 with the complexes of 19 and 20.
- Sunjic, Vitomir,Habus, Ivan,Comisso, Giovanni,Moimas, Flavio
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p. 229 - 234
(2007/10/02)
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- Process for preparing α-hydroxy-acids and compounds obtained by this process
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The invention relates to a process for preparing α-hydroxy-acids of general formula: STR1 in which R represents hydrogen or a lower alkyl radical and Cy represents a phenyl, naphthyl or heterocyclic radical, these latter three radicals optionally comprising one or more substituents selected from the group consisting of lower alkyl, lower alkenyl, lower alkynyl, lower alkoxy radicals and halogen atoms, process which comprises the treatment of an α-monohalogenated ketone of general formula: STR2 in which R and Cy have the same meaning as above and X represents chlorine, bromine or iodine, in the presence of an aqueous solution of an alkali metal hydroxide, a non-polar organic solvent selected from an aromatic or alicyclic hydrocarbon and oxygen in excess optionally in the presence of an inert gas, the treatment being carried out at a temperature ranging from the boiling temperature of the reaction medium at atmospheric pressure and 240° C. under pressure and the alkali metal so formed is then acidified to obtain the desired acid.
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