Day: September 17, 2021

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Ligand exchange between 2 or RuCl23 and (R)- or (S)-BINAP produces BINAP-Ru(II) complexes which act as catalysts for the highly enantioselective hydrogenation of functionalized ketones.

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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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An efficient, highly enantioselective methodology for the synthesis of alpha-phosphanyl ketones 7 and 2-phosphanyl alcohols 12 and 13, important hemilable ligands for enantioselective homogeneous catalysis and chiral building blocks in general, has been developed. The key step of this first enantioselective synthesis of alpha-phosphanyl ketones is the diastereoselective phosphanylation of SAMP hydrazones 2 to produce alpha-phosphanyl hydrazones, isolated as the more stable borane adducts 6. Subsequent ozonolysis afforded alpha-phosphanyl ketones 7. The enantioselective synthesis of 2-phosphanyl alcohols 12 and 13 has been accomplished by two fundamentally different procedures: the phosphanylation of unsubstituted chiral aldehyde hydrazones 9 and the alkylation of alpha-diphenylphopshanyl acetaldehyde SAMP hydrazone 10. After separation of the minor diastereomer, the borane-protected alpha-phosphanyl aldehyde hydrazones 11 were converted to unprotected 2-phosphanyl alcohols 13 by ozonolysis, reduction and removal of the borane group. The absolute configuration of the functionalized phosphanes was determined by X-ray analysis, NOE experiments or polarimetry. VCH Verlagsgesellschaft mbH, 1997.

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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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We have analyzed the effects of mutations inserted during directed evolution of a specialized enzyme, Escherichia coli S-1,2-propanediol oxidoreductase (FucO). The kinetic properties of evolved variants have been determined and the observed differences have been rationalized by modeling the tertiary structures of isolated variants and the wild-type enzyme. The native substrate, S-1,2-propanediol, as well as phenylacetaldehyde and 2S-3-phenylpropane-1,2-diol, which are new substrates accepted by isolated variants, were docked into the active sites. The study provides a comprehensive picture of how acquired catalytic properties have arisen via an intermediate generalist enzyme, which had acquired a single mutation (L259V) in the active site. Further mutagenesis of this generalist resulted in a new specialist catalyst. We have also been able to relate the native enzyme activities to the evolved ones and linked the differences to individual amino acid residues important for activity and selectivity. F254 plays a dual role in the enzyme function. First, mutation of F254 into an isoleucine weakens the interactions with the coenzyme thereby increasing its dissociation rate from the active site and resulting in a four-fold increase in turnover number with S-1,2-propanediol. Second, F254 is directly involved in binding of aryl-substituted substrates via pi-pi interactions. On the other hand, N151 is critical in determining the substrate scope since the side chain amide group stabilizes binding of 1,2-substituted diols and is apparently necessary for enzymatic activity with these substrates. Moreover, the side chain of N151 introduces steric hindrance, which prevents high activity with phenylacetaldehyde. Additionally, the hydroxyl group of T149 is required to maintain the catalytically important hydrogen bonding network. A specialist enzyme, Escherichia coli propanediol oxidoreductase, was subjected to laboratory evolution with the purpose of broadening the substrate scope to include aryl-substituted alcohols and aldehydes. The wild-type enzyme displays very low and undetectable activity with phenylacetaldehyde and 3-phenyl-1,2-propanediol, respectively. Two rounds of directed evolution produced a variant enzyme displaying characteristics of a new specialist and others with traits of generalist enzymes.

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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

Synthetic Route of 538-58-9, 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. 538-58-9, Name is 1,5-Diphenylpenta-1,4-dien-3-one, molecular formula is C17H14O, belongs to chiral-oxygen-ligands compounds. In a Article，once mentioned of 538-58-9

Divinyl ketones (1), prepared by the condensation of acetone with the appropriate aromatic aldehydes, on Michael addition with barbituric and thiobarbituric acids afford the desired spiro compounds (2a-j). The ketoximes (3a-j) obtained from 2a-j on Beckmann transformation by treatment with PCl5 furnish the spiro azepines (4a-j). Alkylation of some of the compounds 2 afford the anticipated N-substituted products (5a-i). Preliminary pharmacological screening of some of the new compounds reveal their anticonvulsant activity.

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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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Different rhodium(III) complexes [Rh(C,C)(P,P)X2]+ bearing both a cis-chelating dicarbene and a diphosphine ligand were synthesized (C,C = methylene(4,4?-diimidazolylidene); P,P = 1,2-bis(diphenylphosphino)ethane (dppe), (R)-(+)-2,2?-bis(diphenylphosphino)-1,1?-binaphthalene (R-BINAP); X = halide, carbanion, NCMe). Solution analysis by NMR spectroscopy indicate a dynamic behavior of the complexes and cis/trans isomerization processes, likely through dissociation of the nonchelating ligands X (X = halide, NCMe), and eventually also involving the diphosphine ligand, identified by the formation of phosphine oxides. The presence of a diphosphine ligand in addition to the dicarbene substantially enhances the catalytic activity of the rhodium center in the transfer hydrogenation of ketones in iPrOH/KOH, reaching over 4000 turnover numbers and turnover frequencies around 1000 h-1 vs 330 h-1 for the phosphine-free analogue. Optimization of the catalytic conditions allowed transfer hydrogenation to be run with only 1 mol % base instead of the often used 10 mol %. The chiral R-BINAP ligand enhances catalytic activity, though no enantioselectivity was induced in the transfer hydrogenation of fluoroacetophenone as prochiral substrate.

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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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Compounds of formula IA or IB are provided where X1, X2 and X3 are independently selected from H or hydroxy protecting groups and R1 is selected from straight or branched chain alkyl groups having from 1 to 8 carbon atoms; straight or branched chain alkenyl groups having from 2 to 8 carbon atoms; straight or branched chain hydroxy-substituted alkyl groups having from 1 to 8 carbon atoms; straight and branched chain hydroxy-substituted alkenyl groups having from 2 to 8 carbon atoms. Such compounds are used in preparing pharmaceutical compositions and are useful in treating a variety of biological conditions.

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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 stereoselective addition of the 2-hydroxyl group of glucose to the mercurated vinyl group of 2-alkenyl glycosides followed by hydride reduction and removal of the saccharide fragment was used to prepare enantiomerically pure 1,2-dihydroxy alkanes. Diols of (R) or (S) configuration can be synthesized from (alpha)-glycosides or the (beta) form respectively. Demercuration with chloride ion led to the insertion of a halo group adjacent to the new chiral center thus allowing for the possibility of further functionalization.

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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 triphenylmethyl group gives very simple access to the 1-protection of 1,2-diol as exemplified by racemic propane-1,2-diol. This group has, however, been shown to be incompatible with lipases commonly used for the resolution of alcohols. This turned out to be the case for Pseudomonas cepacia lipase, which we have used in our earlier work. Lipozyme, a Mucor miehei lipase, best known for 1,3-selectivity with glycerol is, however, shown to catalyze transacetylation onto the secondary hydroxyl group next to a triphenylmethoxy group. The transacetylation is completely enantioselective for the (R)-enantiomer giving a very simple method for the resolution of this type of 1,2-diol enantiomer.

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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

SDS of cas: 19132-06-0, 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. 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

In the reaction of N,N-diethyl-alpha,alpha-difluorobenzylamine (DFBA) with 1,2- or 1,3-diols, selective mono-benzoylation occurs to afford mono-esters of the diols in good yield. The reaction is completed under mild conditions in a short reaction time. Further, prim-, sec-, and tert-diols and catechol can be converted to the corresponding mono-benzoates. DFBA is used for the protection of the hydroxy group in sugars. The selective mono-nicotinylation, formylation and pivaloylation of diols are also performed by using the corresponding difluoroalkylamines.

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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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1,2- and 1,3-Diols are readily protected as cyclic acetals and ketals through a graphene-catalyzed transacetalization process. The methodology features an atom economic procedure since quasi-stoichiometric conditions have been developed. Unlike prior systems, the graphene-catalyzed transacetalization is performed under Br°nsted and Lewis acid-free conditions and without solvent. Our method has been applied to several volatile compounds that are unsuitable for complex work-up and extensive purification steps. The very unusual catalytic properties of graphene for transacetalization reactions are ascribed to molecular charge transfer between graphene and substrates.

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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