Category: chiral-oxygen-ligands

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Tungsten(0)- and rhenium(I)-catalyzed reactions of acetylenic dienol silyl ethers based on the concept of geminal carbo-functionalization of alkynes are reported. Treatment of 3-siloxy-1,3-diene-7-ynes with catalytic amounts of [W(CO)6] or [ReCl(CO)5] under photoirradiation conditions gives synthetically useful bicyclo[3.3.0]octane derivatives in good yields. Extremely high catalytic activity is noted for the rhenium(I) complex. The reaction has been extended to substrates containing a nitrogen atom in their tethers. In this case, two kinds of synthetically useful heterocyclic compounds-the 2-azabicyclo[3.3.0]octane derivatives 9 and the monocyclic dihydropyrroles 10, with allenyl substituents-are obtained, and selective preparation of either product can be achieved through the use of an appropriate combination of the nitrogen substituent and the type of the rhenium(I) catalyst. The 2-azabicyclo[3.3.0]octane derivatives 9 are obtained selectively by carrying out treatment of N-Ns derivatives in the presence of [ReCl(CO) 4(PPh3)], whereas the dihydropyrrole derivatives 10 are obtained by treatment of N-Mbs derivatives with [ReCl(CO)5]/ AgSbF6. Finally, we have applied this geminal carbo-functionalization to one-carbon-elongated substrates containing N-Ts moieties in their tethers. Selective 5-exo cyclization is achieved in the presence of gold(I) or rhenium(I) catalysts, whereas 6-endo cyclization is observed on use of [W(CO) 6]. Geminal carbo-functionalization of 3-siloxy-1,3-dien-7-ynes leading to bicyclo[3.3.0]octane derivatives is achieved through electrophilic activation of alkynes by tungsten(0) and rhenium(I) catalysts (see graphic). Extremely high activity is noted for rhenium(I) catalysts. Furthermore, selective preparation of two different classes of heterocyclic compounds from 5-aza-3-siloxy-1,3-dien-7-ynes is also achieved by appropriate choice of the rhenium(I) catalyst and the protecting group on the nitrogen. Copyright

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

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The present work involves a detailed study of the ultra-violet absorption spectra of various substituted dibenzylidene ketones derived from acetone, ethyl methyl ketone, diethyl ketone, cyclopentanone and cyclohexanone by condensing with several meta- and para-substituted benzaldehydes in n-hexane and in ethanol to ascertain the transition dominant in these solvents. These ketones exist as equilibrium mixtures of s-cis, cis and s-cis, trans conformations. The ultraviolet absorption spectra of the ketones exhibit two bands due to pi* ? pi transition around 250 and 320 nm. The 320 nm band is prominent in all the cases. There is no indication of pi* ? n transition in any of the spectra. The 320 nm band is structureless in all the cases except those shown by the dibenzylidene ketones derived from cyclopentanone in hexane. Therefore it can be inferred that the dibenzylide ketones derived from all the ketones except those derived from cyclopentanone are non-planar.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

Reference of 19132-06-0, Modeling chemical reactions helps engineers virtually understand the chemistry, optimal size and design of the system, and how it interacts with other physics that may come into play. 19132-06-0, Name is (2S,3S)-Butane-2,3-diol, molecular formula is C4H10O2, belongs to chiral-oxygen-ligands compounds. In a Article，once mentioned of 19132-06-0

Lipase from Pseudomonas capacia (PCL, Amano PS) catalyzed the enantioselective diacetylation of (+/-)-2,3-butanediol in vinyl acetate.Both acetylation steps favored the (R)-enantiomer (E1 = 12, E2 = 34), thus the reaction is a sequential kinetic resolution.The enantioselectivities of the two steps reinforced one another because both steps proceeded at comparable rates (S = 3) yielding an overall enantioselectivity of approximately 200.A synthetic-scale resolution starting from 2.7 g of (+/-)-2,3-butanediol yielded the diacetate ester of (R)-(-)-butanediol with 96percent ee (1.6 g, 30percent yield) and (S)-(+)-butanediol with 99percent ee (0.63 g, 23percentyield).This preparation is carried out entirely in organic solvent, thereby avoiding the difficult and low yield extraction of 2,3-butanediol from aqueous solution.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

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Carboxylic acid reductases (CARs) catalyze the reduction of a broad range of carboxylic acids into aldehydes, which can serve as common biosynthetic precursors to many industrial chemicals. This work presents the systematic biochemical characterization of five carboxylic acid reductases from different microorganisms, including two known and three new ones, by using a panel of short-chain dicarboxylic acids and hydroxy acids, which are common cellular metabolites. All enzymes displayed broad substrate specificities. Higher catalytic efficiencies were observed when the carbon chain length, either of the dicarboxylates or of the terminal hydroxy acids, was increased from C2 to C6. In addition, when substrates of the same carbon chain length are compared, carboxylic acid reductases favor hydroxy acids over dicarboxylates as their substrates. Whole-cell bioconversions of eleven carboxylic acid substrates into the corresponding alcohols were investigated by coupling the CAR activity with that of an aldehyde reductase in Escherichia coli hosts. Alcohol products were obtained in yields ranging from 0.5 % to 71 %. The de novo stereospecific biosynthesis of propane-1,2-diol enantiomer was successfully demonstrated with use of CARs as the key pathway enzymes. E. coli strains accumulated 7.0 mm (R)-1,2-PDO (1.0 % yield) or 9.6 mm (S)-1,2-PDO (1.4 % yield) from glucose. This study consolidates carboxylic acid reductases as promising enzymes for sustainable synthesis of industrial chemicals.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

Reference of 4254-15-3, Chemical engineers work across a number of sectors, processes differ within each of these areas, but chemistry and chemical engineering roles are found throughout, and are directly involved in the process of chemical products and materials. 4254-15-3, Name is (S)-Propane-1,2-diol, molecular formula is C3H8O2, belongs to chiral-oxygen-ligands compounds. In a Article，once mentioned of 4254-15-3

The enantiomers of proxyphylline have been separated via their corresponding camphanates. Synthesis of (+)-proxyphylline from theophylline and (S)-propylene oxide derived from (S)-lactic acid established the absolute configuration of the (+) and (-) isomer as S and R, respectively. The activity of the enantiomers as cyclic nucleotide phosphodiesterase inhibitors was tested in human lung tissue homogenate. No differences were found either between the two enantiomers or between the enantiomers and racemic proxyphylline.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

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(S)-Camphanate of furfuryl alcohol undergoes Diels-Alder addition in molten maleic anhydride giving one major crystalline adduct (+)-2 ((1S,1S’,2R,3S,4R)-1-[(camphanoyloxy)methyl]-7-oxabicyclo[2.2.1]hept-5 -ene-2-exo,3-exo-dicarboxylic anhydride), the absolute configuration of which was established through chemical correlation. Adduct (+)-2 was converted into an enantiomerically pure intermediate as in Yadav’s approach to the synthesis of taxol analogues. Copyright (C) Elsevier Science Ltd.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

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The hydrogenation of carboxylic acid derivatives at room temperature was investigated. With a mixed Rh/Pt oxide (Nishimura catalyst), low to medium activity was observed for various alpha-amino and alpha-hydroxy esters. At 100 bar hydrogen pressure and 10% catalysts loading, high yields of the desired amino alcohols and diols were obtained without racemization. The most suitable alpha-substituents were NH2, NHR, and OH, whereas beta-NH2 were less effective. Usually, aromatic rings were also hydrogenated, but with the free bases of amino acids as substrates, some selectivity was observed. No reaction was found for alpha-NR2, alpha-OR, and unfunctionalized esters; acids and amides were also not reduced under these conditions. A working hypothesis for the mode of action of the catalyst is presented.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

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Four kinds of ferroelectric liquid crystals (FLCs) possessing OH groups, ((S)-2-methylbutyl 4-<4-(11-hydroxyundecyloxy)benzylideneamino>cinnamate 4a, (S)-2-methylbutyl 4-<4-(11-hydroxyundecyloxy)-2-hydroxybenzylideneamino>cinnamate 4b, (S)-2-hydroxypropyl 4-<4-(11-hydroxyundecyloxy)benzylideneamino>cinnamate 4c, and (S)-2-hydroxypropyl 4-<4-(11-hydroxyundecyloxy)-2-hydroxybenzylideneamino>cinnamate 4d) were prepared in order to understand how the introduction of OH groups in FLCs affect the phase behavior and electrooptical compounds 4a and 4b.Comparing 4b and 4d both of which have an OH group at the o-position of the benzylidene group with 4a dn 4c, the former samples show a higher SA-isotropization (I) transition temperature than do the latter ones.It is suggested from IR spectroscopic results that inter- and intramolecular hydrogen bonding contribute to the stabilization of the SA phase.The order of the helical pitch in the chiral smectic C (Sc*) phase was found to be 4b>4a>4d>4c within 1.8 – 6.6 mum.From an electrooptical effect due to a deformation of the helical structure in the Sc phase, the rise time of the surface director (tausr) and the rise time of the bulk director (taubr) were measured to be as follows: tausr are 850, 1500, 30 and 70 mus, and taubr are 12, 100, 0.17, and 0.35 ms for 4a, 4b, 4c, and 4d, respectively.It was found that the intramolecular hydrogen bonding results in a slower optical response time, whereas intermolecular hydrogen bonding results in a faster one.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

Reference of 24621-61-2, Academic researchers, R&D teams, teachers, students, policy makers and the media all rely on us to share knowledge that is reliable, accurate and cutting-edge. 24621-61-2, Name is (S)-Butane-1,3-diol, molecular formula is C4H10O2, belongs to chiral-oxygen-ligands compounds. In a Article，once mentioned of 24621-61-2

The stereochemical course of the conversion of alpha-ketoisocaproate to beta-hydroxyisovalerate catalysed by the enzyme 4-hydroxyphenylpyruvate dioxygenase is described.

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Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate

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Tandem anionic oxy-Cope rearrangement/radical oxygenation reactions provide delta,?-unsaturated alpha-(aminoxy) carbonyl compounds, which serve as convenient precursors to diverse compound classes. Functionalized carbocycles are accessible by very rare all-carbon 5-endo-trig cyclizations, but also common 5-exo-trig radical cyclizations, based on the persistent radical effect. The tandem reactions can be further extended by highly diastereoselective allylation or reduction steps to give complex scaffolds.

The result showed that such a combination of chemo- and biocatalysis improved the catalytic yield more than two times compared with that of sole metal catalysis.I hope my blog about 538-58-9 is helpful to your research. Application In Synthesis of 1,5-Diphenylpenta-1,4-dien-3-one

Reference：
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate