Aminomethylation of BINOL with methyleneiminium salts

2011 ◽  
Vol 89 (11) ◽  
pp. 1319-1324 ◽  
Author(s):  
Gennady Shustov ◽  
Vladimir Khlebnikov
Keyword(s):  
Enantiomeric Excess ◽  
New Method ◽  
Reaction Conditions

A new method for synthesizing chiral 3,3′-bis(N,N-dialkylaminomethyl)-1,1′-bi-2-naphthols with high enantiomeric excess is described. The procedure consists of bis-lithiation of diprotected (S)- or (R)-1,1′-bis(2-naphthol) followed by treatment of the intermediate with methyleneiminium salts. Mild reaction conditions prevent racemization and provide 3,3′-bis(N,N-dialkylaminomethyl)-1,1′-bi-2-naphthols or 3-(N,N-dialkylaminomethyl)-1,1′-bi-2-naphthols with an enantiomeric excess >99%.

Enantioselective alpha-Arylation of Benzamides via Synergistic Nickel and Metallaphotoredox Catalysis

2019 ◽  
Author(s):  
John Montgomery ◽  
Alexander W. Rand
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Enantiomeric Excess ◽  
New Method ◽  
Aryl Bromides

A new method to access alpha-arylated benzamides has been enabled by metallaphotoredox catalysis. This system allows for non-directed C–H functionalization of N-alkyl benzamides using a dual nickel/iridium catalytic system to form tertiary stereocenters in good enantiomeric excess and moderate yields. This reaction shows excellent functional group compatibility and can be performed using a number of sterically and electronically different aryl bromides and secondary benzamides.

Enantioselective alpha-Arylation of Benzamides via Synergistic Nickel and Metallaphotoredox Catalysis

2019 ◽  
Author(s):  
John Montgomery ◽  
Alexander W. Rand
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Enantiomeric Excess ◽  
New Method ◽  
Aryl Bromides

A new method to access alpha-arylated benzamides has been enabled by metallaphotoredox catalysis. This system allows for non-directed C–H functionalization of N-alkyl benzamides using a dual nickel/iridium catalytic system to form tertiary stereocenters in good enantiomeric excess and moderate yields. This reaction shows excellent functional group compatibility and can be performed using a number of sterically and electronically different aryl bromides and secondary benzamides.

scholarly journals Design of Iridium N-Heterocyclic Carbene Amino Acid Catalysts for Asymmetric Transfer Hydrogenation of Aryl Ketones

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 671
Author(s):  
Chad M. Bernier ◽  
Joseph S. Merola
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Enantiomeric Excess ◽  
Transfer Hydrogenation ◽  
Acid Catalysts ◽  
Asymmetric Transfer Hydrogenation ◽  
Reaction Conditions ◽  
Chiral Complexes ◽  
Acetophenone Derivatives ◽  
Aryl Ketones

A series of chiral complexes of the form Ir(NHC)2(aa)(H)(X) (NHC = N-heterocyclic carbene, aa = chelated amino acid, X = halide) was synthesized by oxidative addition of -amino acids to iridium(I) bis-NHC compounds and screened for asymmetric transfer hydrogenation of ketones. Following optimization of the reaction conditions, NHC, and amino acid ligands, high enantioselectivity was achieved when employing the Ir(IMe)2(l-Pro)(H)(I) catalyst (IMe = 1,3-dimethylimidazol-2-ylidene), which asymmetrically reduces a range of acetophenone derivatives in up to 95% enantiomeric excess.

A Novel and Efficient Alkoxylselenenylation of Alkenes

2019 ◽  
Vol 41 (6) ◽  
pp. 1039-1039
Author(s):  
Yingguo Fang and Jie Yan Yingguo Fang and Jie Yan
Keyword(s):  
Room Temperature ◽  
Electrophilic Addition ◽  
New Method ◽  
Reaction Conditions ◽  
Selenium Species

A novel and efficient alkoxylselenenylation from alkenes, diselenides, and alcohols mediated by iodine is developed, with which a series of β-alkoxy selenides are synthesized. In this procedure, firstly, I2 reacts with diselenide to form in situ the active electrophilic selenium species RSeI, then following an electrophilic addition of it to alkenes provides β-alkoxy selenides with high regioselectivity and in good yields. This new method for achieving β-alkoxy selenides has some advantages over other methods such as using available and cheap iodine as the oxidizing species at room temperature, which makes this reaction has milder reaction conditions and simpler procedure.

scholarly journals (S)-Pramipexole and Its Enantiomer, Dexpramipexole: A New Chemoenzymatic Synthesis and Crystallographic Investigation of Key Enantiomeric Intermediates

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 941
Author(s):  
Samuele Ciceri ◽  
Patrizia Ferraboschi ◽  
Paride Grisenti ◽  
Shahrzad Reza Elahi ◽  
Carlo Castellano ◽  
...  
Keyword(s):  
Single Crystal ◽  
Enantiomeric Excess ◽  
Three Dimensional ◽  
Building Blocks ◽  
Chemoenzymatic Synthesis ◽  
Racemic Mixture ◽  
Candida Antarctica Lipase ◽  
Crystallographic Investigation ◽  
Reaction Conditions ◽  
X Ray

A new chemoenzymatic method has been developed for the synthesis of (S)- and (R)-N-(6-hydroxy-4,5,6,7-tetrahydrobenzo[d]thiazol-2-yl) acetamide, two key synthons for the preparation of (S)-pramipexole, an anti-Parkinson drug, and its enantiomer dexpramipexole, which is currently under investigation for the treatment of eosinophil-associated disorders. These two building blocks have been obtained in good yields and high enantiomeric excess (30% and >98% ee for the R-enantiomer, and 31% and >99% ee for the S- one) through a careful optimization of the reaction conditions, starting from the corresponding racemic mixture and using two consecutive irreversible transesterifications, catalyzed by Candida antarctica lipase type A. Single crystal X-ray analysis has been carried out to unambiguously define the stereochemistry of the two enantiomers, and to explore in depth their three-dimensional features.

scholarly journals Rigid and concave, 2,4-cis-substituted azetidine derivatives: A platform for asymmetric catalysis

2018 ◽  
Author(s):  
Akina Yoshizawa ◽  
Antonio Feula ◽  
Louise Male ◽  
Andrew G. Leach ◽  
John Fossey
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Asymmetric Catalysis ◽  
Enantiomeric Excess ◽  
Platinum Complex ◽  
Crystal Structure Analysis ◽  
Single Crystal Structure ◽  
Complex Catalyst ◽  
Reaction Conditions ◽  
Absolute Stereochemistry

A series of single enantiomer, 2,4-<i>cis</i>-disubstituted amino azetidines were synthesised and used as ligands for copper-catalysed Henry reactions of aldehydes with nitromethane. Optimisation of ligand substituents and the reaction conditions was conducted. The enantiomeric excess of the formed products was highest when alkyl aldehydes were employed in the reaction (>99% e.e.). The absolute stereochemistry of one representative azetidine derivative salt was determined by analysis of the Flack parameter of an XRD single crystal structure. The origin of selectivity in catalysis was investigated computationally, revealing the importance of the amino-substituent in determining the stereochemical outcome. A racemic platinum complex of a <i>cis</i>-disubstituted azetidine is examined by XRD single crystal structure analysis with reference to its steric parameters, and analogies to the computationally determined copper complex catalyst are drawn.<br>

Plasma cholinesterase phenotyping with use of visible-region spectrophotometry.

1986 ◽  
Vol 32 (1) ◽  
pp. 194-197 ◽  
Author(s):  
M H Abernethy ◽  
P M George ◽  
J L Herron ◽  
R T Evans
Keyword(s):  
Cholinesterase Activity ◽  
Visible Region ◽  
Plasma Cholinesterase ◽  
Choline Oxidase ◽  
New Method ◽  
Absorption Curve ◽  
Differential Inhibition ◽  
Reaction Conditions ◽  
Activity Measurements

Abstract A method that overcomes the difficulties of the 240-nm benzoylcholine method for phenotyping plasma cholinesterases has been developed. After a timed reaction, under the same reaction conditions as in the classic procedure, choline is detected at 500 nm by use of choline oxidase coupled with the peroxidase/phenol/aminoantipyrine system. Cholinesterase activity measurements, calibrated by use of choline iodide as standard, are linearly related to results obtained with propionylthiocholine as substrate at 25 degrees C (y = 0.14x + 0.17, n = 30, r = 0.98). Results of differential inhibition with dibucaine and fluoride are virtually identical with those obtained by the ultraviolet method (y = 0.97x + 4.3, r = 0.995, and y = 0.93x - 0.5, r = 0.987, respectively) and give the same classification of homo- and heterozygotes for the usual, atypical, and fluoride-resistant variants. The new method has substantial advantages in that it eliminates the difficulties associated with measuring small changes in high absorbances at a suboptimal wavelength on a steep portion of the absorption curve.

Highly enantioselective asymmetric Henry reaction catalyzed by novel chiral phase transfer catalysts derived from cinchona alkaloids

2016 ◽  
Vol 14 (42) ◽  
pp. 10101-10109 ◽  
Author(s):  
Ponmuthu Kottala Vijaya ◽  
Sepperumal Murugesan ◽  
Ayyanar Siva
Keyword(s):  
Phase Transfer ◽  
Enantiomeric Excess ◽  
Cinchona Alkaloids ◽  
Henry Reaction ◽  
Reaction Conditions ◽  
Chiral Phase ◽  
Phase Transfer Catalysts ◽  
Wide Range ◽  
Chiral Phase Transfer Catalysts

Newly synthesized CPTCs are applied in the asymmetric Henry reaction to a wide range of aldehydes under mild reaction conditions, and we obtained higher chemical yields and an excellent enantiomeric excess.

Optimization of Chiral Resolution of (+/-)-1-Phenylethanol by Statistical Methods

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Ganapati D. Yadav ◽  
Jyoti B. Sontakke
Keyword(s):  
Kinetic Resolution ◽  
Batch Reactor ◽  
Immobilized Lipase ◽  
Enantiomeric Excess ◽  
Molar Ratio ◽  
Catalyst Loading ◽  
Acyl Donor ◽  
Reaction Conditions ◽  
Optimum Reaction ◽  
Synthetic Intermediate

Optically active 1-phenylethanol is used as a chiral building block and synthetic intermediate in pharmaceutical and fine-chemical industries. Lipase - catalyzed kinetic resolution of (R,S)-1-phenylethanol with vinyl acetate as an acyl donor and Candida antarctica immobilized lipase as a biocatalyst in a batch reactor was optimized using Response Surface Methodology (RSM). Four-factor-five-level central composite rotatable design (CCRD) was employed to evaluate the effect of synthesis parameters such as speed of agitation, enzyme loading, temperature and acyl donor/alcohol molar ratio, on conversion, enantiomeric excess (ee), enantioselectivity and initial rate. Optimum reaction conditions obtained were; mole ratio of acyl donor: ester of 2:1, temperature of 42.5 °C, catalyst loading of 1.6x10-3 g.cm-3 and speed of agitation of 336 rpm. Analysis of variance was performed to determine significantly affecting variables and interactions between the process parameters.

A new method for preparation of 1-(4-substituted phenyl)-6-phenyl-2-thiouracils via cyclization of N-(4-substituted phenyl)-N'-3-phenylpropenoylthioureas and Dimroth rearrangement of 2-(4-substituted phenylimino)-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones

1987 ◽  
Vol 52 (9) ◽  
pp. 2260-2265 ◽  
Author(s):  
Milan Dzurilla ◽  
Peter Kutschy ◽  
Dušan Koščík
Keyword(s):  
Boron Trifluoride ◽  
Lithium Hydride ◽  
New Method ◽  
Dimroth Rearrangement ◽  
Reaction Conditions

N-(4-Substituted phenyl)-N'-3-phenylpropenoylthioureas treated with lithium hydride afforded 1-(4-substituted phenyl)-6-phenyl-2-thiouracils; these could also be obtained by Dimroth rearrangement of 2-(4-substituted phenylimino)-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones under the same reaction conditions. 2-(4-Substituted phenylimino)-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones were synthesized from the corresponding thioureas under catalysis of boron trifluoride in chloroform.

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