Manganese(iii) acetate-mediated alkylation of β-keto esters and β-keto amides: an enantio- and diastereo-selective approach to substituted pyrrolidinones

2002 ◽  
Vol 1 (2) ◽  
pp. 373-380 ◽  
Author(s):  
Gregory Bar ◽  
Andrew F. Parsons ◽  
C. Barry Thomas
Keyword(s):  
Keto Esters ◽  
Selective Approach

Towards Enantioselective Electrophilic Trifluoromethylation of β-Keto Esters

2006 ◽  
Author(s):  
Dominique Cahard ◽  
Jun-An Ma ◽  
Vitaliy Petrik
Keyword(s):  
Keto Esters

Toward An Islamic Alternative In Thought and Knowledge

1989 ◽  
Vol 6 (1) ◽  
pp. 1-12
Author(s):  
Taha Jabir Al Alwani
Keyword(s):  
Present State ◽  
Traditional Approach ◽  
World View ◽  
Cultural Transformation ◽  
Modern Culture ◽  
Selective Approach ◽  
Cultural Systems ◽  
Eclectic Approach ◽  
Basic Approaches ◽  
The Many

IntroductionCurrent developments and the many acute problems facing the MuslimUmmah, especially at the intellectual level, present a serious challenge toIslam. This is why an attempt to outline an intellectual Islamic alternativein thought and knowledge has never been so urgent and imperative. Thiwill, insha 'Allah, help in formulating a clear and coordinated policy withregard to cultural transformation based on firm principles and sound strategy.It is also hoped that this policy will lead to scientific findings.By way of introduction, I will give a brief description of the state ofknowledge and thought. and of the educational and cultural systems in thecontemporary Arab and Muslim world.The Present State of ThoughtWhen examining the present state of thought among the Muslim peoples.three basic approaches can be identified:• The first can be described as the traditionalist approach which,by and large, considers the "traditional'' thought of the Ummahto be self-sufficient and capable of being presented asit is or with very little alteration. This approach suggeststhat the Ummah's contemporary intellectual life can be formedand organized and that the structure of its civilization canbe built on this basis. This approach i often described asthe approach of authenticity.• The second approach considers contemporary Western thoughtand its world-view-its concepts of existence, of life and ofman-to be universal, without it a modern culture and civilizationcannot be built. This tendency maintains that Westernthought must be adopted in toto, and any consequent negativeaspects are the price that must be paid if a modern cultureand civilization are to be established. This view is oftendescribed as mcdemistic.• The third trend, or the eclectic approach, advocates yetanother view. It contends that one must select from traditionalthought what is most sound, and from "modern" contemporarythought that which one considers and proves tobe correct, and weld the two to form an intellectual structurethat will provide a guaranteed basis for achieving what isrequired.However, the traditional approach, in the manner it has been presentedand applied, did not help to prevent the Ummah from falling into Lhe stateof decline and failure from which it is still suffering. Likewise, Western thought,as it also is presented and applied, cannot protect the Ummah from its inherentadverse, harmful and even disastrous effects. The advocates of theeclectic selective approach have not yet presented the details of this proposedblend, let alone tried to put it into effect. All this is conducive to the widerangingquestion: Is the Umrnah going through a serious intellectual crisis;and . if so, what is the way out of it? ...

Diastereoselective Reduction of Selected α-substituted β-keto Esters and the Assignment of the Relative Configuration by 1H-NMR Spectroscopy

2020 ◽  
Vol 07 ◽  
Author(s):  
Christian Trapp ◽  
Corinna Schuster ◽  
Chris Drewniok ◽  
Dieter Greif ◽  
Martin Hofrichter
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Selective Reduction ◽  
Reducing Agents ◽  
Relative Configuration ◽  
Curtius Rearrangement ◽  
Keto Esters ◽  
Hydroxy Esters ◽  
Diastereoselective Reduction

Background:: Chiral β-hydroxy esters and α-substituted β-hydroxy esters represent versatile building blocks for pheromones, β-lactam antibiotics and 1,2- or 1,3-aminoalcohols. Objective:: Synthesis of versatile α-substituted β-keto esters and their diastereoselective reduction to the corresponding syn- or anti-α-substituted β-hydroxy esters. Assignment of the relative configuration by NMR-spectroscopy after a CURTIUS rearrangement of α-substituted β-keto esters to 4-substituted 5-methyloxazolidin-2-ones. Method:: Diastereoselective reduction was achieved by using different LEWIS acids (zinc, titanium and cerium) in combination with complex borohydrides as reducing agents. Assignment of the relative configuration was verified by 1H-NMR spectroscopy after CURTIUS-rearrangement of α-substituted β-hydroxy esters to 4-substituted 5-methyloxazolidin-2-ones. Results:: For the syn-selective reduction, titanium tetrachloride (TiCl4) in combination with a pyridine-borane complex (py BH3) led to diastereoselectivities up to 99% dr. High anti-selective reduction was achieved by using cerium trichloride (CeCl3) and steric hindered reducing agents such as lithium triethylborohydride (LiEt3BH). After CURTIUS-rearrangement of each α-substituted β-hydroxy ester to the corresponding 4-substituted 5-methyloxazolidin-2-one, the relative configuration was confirmed by 1H NMR-spectroscopy. Conclusion:: We have expanded the procedure of LEWIS acid-mediated diastereoselective reduction to bulky α-substituents such as the isopropyl group and the electron withdrawing phenyl ring.

Syntheses of .alpha.-, .beta.-, and .gamma.-substituted carnitines via .beta.-keto esters

1985 ◽  
Vol 50 (19) ◽  
pp. 3627-3631 ◽  
Author(s):  
Carla A. Hosmer ◽  
Robert N. Comber ◽  
Wayne J. Brouillette
Keyword(s):  
Keto Esters ◽  
Alpha Beta

Fast, solvent-free and highly enantioselective fluorination of β-keto esters catalyzed by chiral copper complexes in a ball mill

2017 ◽  
Vol 19 (7) ◽  
pp. 1674-1677 ◽  
Author(s):  
Yifeng Wang ◽  
Haojiang Wang ◽  
Yidong Jiang ◽  
Cheng Zhang ◽  
Juanjuan Shao ◽  
...  
Keyword(s):  
Ball Mill ◽  
Copper Complexes ◽  
Solvent Free ◽  
Planetary Ball Mill ◽  
Keto Esters ◽  
Solvent Free Conditions

A fast and highly enantioselective fluorination of β-keto esters catalyzed by diphenylamine linked bis(oxazoline)-Cu(OTf)2 complexes under solvent-free conditions has been developed using a planetary ball mill.

Extending Screening in “Elderly” Patients: Should We Consider a Selective Approach?

2020 ◽  
Vol 20 (5) ◽  
pp. 377-381
Author(s):  
Eugenia C. Ip ◽  
Ruben B. Cohen-Hallaleh ◽  
Alexander K. Ng
Keyword(s):  
Elderly Patients ◽  
Selective Approach

scholarly journals The COOL-Process—A Selective Approach for Recycling Lithium Batteries

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 259
Author(s):  
Sandra Pavón ◽  
Doreen Kaiser ◽  
Robert Mende ◽  
Martin Bertau
Keyword(s):  
Lithium Ion ◽  
Global Market ◽  
Raw Material ◽  
Mass Ratio ◽  
Reaction Conditions ◽  
Cool Process ◽  
Secondary Sources ◽  
Selective Approach ◽  
Valuable Metals ◽  
Housing Materials

The global market of lithium-ion batteries (LIB) has been growing in recent years, mainly owed to electromobility. The global LIB market is forecasted to amount to $129.3 billion in 2027. Considering the global reserves needed to produce these batteries and their limited lifetime, efficient recycling processes for secondary sources are mandatory. A selective process for Li recycling from LIB black mass is described. Depending on the process parameters Li was recovered almost quantitatively by the COOL-Process making use of the selective leaching properties of supercritical CO2/water. Optimization of this direct carbonization process was carried out by a design of experiments (DOE) using a 33 Box-Behnken design. Optimal reaction conditions were 230 °C, 4 h, and a water:black mass ratio of 90 mL/g, yielding 98.6 ± 0.19 wt.% Li. Almost quantitative yield (99.05 ± 0.64 wt.%), yet at the expense of higher energy consumption, was obtained with 230 °C, 4 h, and a water:black mass ratio of 120 mL/g. Mainly Li and Al were mobilized, which allows for selectively precipitating Li2CO3 in battery grade-quality (>99.8 wt.%) without the need for further refining. Valuable metals, such as Co, Cu, Fe, Ni, and Mn, remained in the solid residue (97.7 wt.%), from where they are recovered by established processes. Housing materials were separated mechanically, thus recycling LIB without residues. This holistic zero waste-approach allows for recovering the critical raw material Li from both primary and secondary sources.

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