Transition-Metal-Free Enantioselective Reactions of Organo­magnesium Reagents Mediated by Chiral Ligands

Synthesis ◽  
2018 ◽  
Vol 50 (18) ◽  
pp. 3589-3602
Author(s):  
Anne Boussonnière ◽  
Anne-Sophie Castanet ◽  
Hélène Guyon
Keyword(s):  
Short Review ◽  
Allylic Alkylation ◽  
Nucleophilic Additions ◽  
Chiral Ligand ◽  
Substitution Reactions ◽  
The Past ◽  
Great Utility ◽  
Carbon Carbon Bonds ◽  
Enantioselective Reactions ◽  
Magnesium Exchange

Organomagnesium reagents are among the most important reagents in organic chemistry because of their great utility in forming carbon–carbon bonds. Although most enantioselective reactions using these organometallics involve transmetalation, the past decade has witnessed impressive advances in direct chiral-ligand-mediated reactions of organomagnesiums­. This short review presents an overview of these achievements in enantioselective nucleophilic additions and substitutions.1 Introduction2 Enantioselective Nucleophilic Additions2.1 Addition to C=O Bonds2.2 Addition to C=N Bonds2.3 Addition to C=C Bonds3 Enantioselective Substitution Reactions3.1 Sulfoxide–Magnesium Exchange3.2 Desymmetrization via Anhydride Opening3.3 Asymmetric Allylic Alkylation (AAA)4 Conclusion

Asymmetric Rhodium-Catalyzed Allylic Substitution Reactions with Nitrile-Stabilized Carbanions

Synlett ◽  
2021 ◽  
Author(s):  
Mai-Jan Tom ◽  
P. Andrew Evans
Keyword(s):  
Biologically Active ◽  
Allylic Alkylation ◽  
Substitution Reactions ◽  
Stereogenic Centers ◽  
Enantioselective Reactions ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Alkylation Reactions ◽  
Quaternary Stereogenic Centers ◽  
Selective Access

This Account summarizes our recent work on rhodium-catalyzed allylic alkylation reactions with nitrile-stabilized carbanions. Despite the challenges associated with employing nitrile stabilized nucleophiles in transition-metal-catalyzed reactions, we recently developed both enantiospecific and enantioselective allylic alkylation reactions. Notably, these novel reactions permit the expedient and selective access to an array of acyclic ternary and quaternary stereogenic centers that are present in important biologically active molecules. 1 Introduction 2 Enantiospecific Reactions of Nitrile-Stabilized Anions 3 Enantioselective Reactions of Nitrile-Stabilized Anions 4 Conclusion

ON "PLASTIC" WAVES IN SOLIDS

1959 ◽  
Vol 37 (9) ◽  
pp. 1017-1035 ◽  
Author(s):  
John M. Bowsher
Keyword(s):  
Theoretical Study ◽  
Short Review ◽  
Future Research ◽  
Past Work ◽  
The Past ◽  
Engineering Significance ◽  
The Subject

The study of the propagation of "plastic" waves in solids has reached a stage where it is necessary to consider which direction future research should take. In the past 90 or so years many experiments, mostly designed to elucidate certain points of engineering significance, and a few attempts at a theoretical study have cast some light on the subject and revealed it as one of formidable difficulty.Nearly all the experiments have of necessity relied on rather dubious theories for their interpretation, and part of the present paper will be devoted to a description of an apparatus which gives results capable of being interpreted with a very minimum of theory. The remainder of the paper is devoted to a short review of past work with particular emphasis on basic phenomena and to a brief discussion on the most pressing problems still remaining. The experiments described in the present paper bring to light a factor in the propagation of "plastic" waves that seems to have been overlooked in previous work.

scholarly journals A Quantum-Chemical DFT Approach to Elucidation of the Chirality Transfer Mechanism of the Enantioselective Suzuki–Miyaura Cross-Coupling Reaction

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Radomir Jasiński ◽  
Oleg M. Demchuk ◽  
Dmytro Babyuk
Keyword(s):  
Quantum Chemical ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Palladium Complexes ◽  
Initial Reaction ◽  
Chiral Ligand ◽  
Chirality Transfer ◽  
Cross Coupling Reaction ◽  
Enantioselective Reactions ◽  
Selection Of

The DFT calculations of the simplified model of the asymmetric Suzuki–Miyaura coupling reaction were performed at the M062x/LANL2DZ theory level at first. It was found that enantioselective reactions mediated by the palladium complexes of chiral C,P-ligands follow a four-stage mechanism similar to that proposed previously as one of the most credible mechanisms. It should be underlined that the presence of substituents in the substrates and the chiral ligand at ortho positions determines the energies of possible diastereoisomeric transition states and intermediates in initial reaction steps. This suggests that, in practice, a sharp selection of theoretically possible paths of chirality transfer from the catalyst to the product should have a place and, therefore, the absolute configuration of the formed atropisomeric product is defined and can be predicted.

scholarly journals Brief structural insight into the allosteric gating mechanism of BK (Slo1) channel

2019 ◽  
Vol 97 (6) ◽  
pp. 498-502
Author(s):  
János Almássy ◽  
Péter P. Nánási
Keyword(s):  
Quaternary Structure ◽  
Short Review ◽  
Bk Channel ◽  
The Past ◽  
Gating Model ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Electrophysiological Measurements ◽  
Structural Insight ◽  
Insight Into

The big conductance Ca2+-dependent K+ channel, also known as BK, MaxiK, Slo1, or KCa1.1, is a ligand- and voltage-gated K+ channel. Although structure-function studies of the past decades, involving mutagenesis and electrophysiological measurements, revealed fine details of the mechanism of BK channel gating, the exact molecular details remained unknown until the quaternary structure of the protein has been solved at a resolution of 3.5 Å using cryo-electron microscopy. In this short review, we are going to summarize these results and interpret the gating model of the BK channel in the light of the recent structural results.

Some Aspects of S.S.T. Operations in Non-optimum Conditions

1966 ◽  
Vol 19 (3) ◽  
pp. 324-330
Author(s):  
P. S. Cole
Keyword(s):  
Short Review ◽  
Relative Cost ◽  
Optimum Conditions ◽  
The Past ◽  
Cost Penalty

Over the past few years, numerous papers have been written concerning various aspects of S.S.T. operations, the majority dealing with one or two facets. This short review considers those aspects which are of major importance when the S.S.T. is operated in non-optimum conditions and an attempt is made to indicate the relative cost penalty caused by the phenomena discussed, the performance in smooth standard conditions being taken as the datum. Little of the information presented is new and most of the points mentioned are considered in greater detail in the references. (Crown copyright, reproduced with the permission of H.M.S.O.)

Iron-Catalyzed Cross-Coupling: Mechanistic Insight for Rational Applications in Synthesis

Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3269-3280 ◽  
Author(s):  
Tobias Parchomyk ◽  
Konrad Koszinowski
Keyword(s):  
Catalyst Activity ◽  
Cross Coupling ◽  
Short Review ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Open Questions ◽  
Carbon Carbon Bonds ◽  
Bond Homolysis ◽  
Molecular Complexity ◽  
Synthetic Application

Iron-catalyzed cross-coupling reactions provide a promising way to form new carbon–carbon bonds and build up molecular complexity. This short review presents recent advances in the synthetic application of these reactions as well as in the elucidation of their mechanism. It also highlights remaining problems and aims at pointing out ways toward possible remedies.1 Introduction2 Synthesis: Recent Accomplishments and Unsolved Problems2.1 Substrate Scope: Electrophiles2.2 Substrate Scope: Nucleophiles2.3 Catalyst Activity and Chemoselectivity2.4 Stereoselectivity2.5 Practical Aspects3 Mechanism: Recent Insights and Open Questions3.1 Transmetallation and Activation of the Iron Precatalyst3.2 Coupling via Oxidative Addition and Reductive Elimination3.3 Coupling via C–X Bond Homolysis and Radical Rebound3.4 Coupling via Bimolecular C–X Bond Homolysis3.5 Other Reactions of Organoiron Species with Electrophiles4 Toward Rational Reaction Improvement5 Conclusion

scholarly journals Research journey of respirasome

2020 ◽  
Vol 11 (5) ◽  
pp. 318-338 ◽  
Author(s):  
Meng Wu ◽  
Jinke Gu ◽  
Shuai Zong ◽  
Runyu Guo ◽  
Tianya Liu ◽  
...  
Keyword(s):  
Short Review ◽  
Research Field ◽  
Atomic Scale ◽  
Inner Mitochondrial Membrane ◽  
Macroscopic Scale ◽  
The Past ◽  
Transport Chain ◽  
High Resolution Structure ◽  
New Perspective ◽  
Resolution Structure

AbstractRespirasome, as a vital part of the oxidative phosphorylation system, undertakes the task of transferring electrons from the electron donors to oxygen and produces a proton concentration gradient across the inner mitochondrial membrane through the coupled translocation of protons. Copious research has been carried out on this lynchpin of respiration. From the discovery of individual respiratory complexes to the report of the high-resolution structure of mammalian respiratory supercomplex I1III2IV1, scientists have gradually uncovered the mysterious veil of the electron transport chain (ETC). With the discovery of the mammalian respiratory mega complex I2III2IV2, a new perspective emerges in the research field of the ETC. Behind these advances glitters the light of the revolution in both theory and technology. Here, we give a short review about how scientists ‘see’ the structure and the mechanism of respirasome from the macroscopic scale to the atomic scale during the past decades.

Nitrosoalkenes: Underappreciated Reactive Intermediates for Formation of Carbon–Carbon Bonds

Synlett ◽  
2019 ◽  
Vol 30 (16) ◽  
pp. 1855-1866 ◽  
Author(s):  
Steven M. Weinreb
Keyword(s):  
Natural Product Synthesis ◽  
Addition Reactions ◽  
Conjugate Additions ◽  
Carbon Nucleophiles ◽  
The Past ◽  
Carbon Carbon Bonds ◽  
Intramolecular Reactions ◽  
Intermolecular Reactions ◽  
Key Steps ◽  
Synthetic Approaches

This Account describes studies carried out by my group during the past decade on both intra- and intermolecular conjugate additions of carbon nucleophiles to nitrosoalkenes. Using the Denmark protocol for the generation of nitrosoalkenes from α-chloro-O-silyloximes, a number of bridged and fused bicyclic ring systems can be prepared via the intramolecular version of this process. Intermolecular conjugate addition reactions of nitrosoalkenes with a wide variety of ester enolates as coupling partners can also be achieved efficiently using a similar procedure. Some stereochemical aspects of these nucleophilic additions have been studied with both acyclic and cyclic nitrosoalkenes. This methodology has been applied as key steps in synthetic approaches to some complex indole and Myrioneuron alkaloids.1 Introduction2 Conjugate Additions of Nitrosoalkenes2.1 Background2.2 Intramolecular Reactions2.3 Intermolecular Reactions2.4 Stereochemical Aspects3 Applications to Natural Product Synthesis3.1 Angustilodine and Related Alkaloids3.2 Approach to Apparicine-Type Alkaloids3.3 Myrioneurinol4 Summary and Outlook

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