ChemInform Abstract: Enantiomer Recognition of Organic Ammonium Salts by Podand- and Crown- Type Monensin Amides: New Synthetic Strategy for Chiral Receptors.

ChemInform ◽  
2010 ◽  
Vol 23 (21) ◽  
pp. no-no
Author(s):  
K. MARUYAMA ◽  
H. SOHMIYA ◽  
H. TSUKUBE
Keyword(s):  
Ammonium Salts ◽  
Synthetic Strategy ◽  
Chiral Receptors

Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

2018 ◽  
Author(s):  
Erin Stache ◽  
Alyssa B. Ertel ◽  
Tomislav Rovis ◽  
Abigail G. Doyle
Keyword(s):  
Carboxylic Acids ◽  
Functional Groups ◽  
Single Step ◽  
Direct Access ◽  
Photoredox Catalysis ◽  
Acyl Radical ◽  
Synthetic Strategy ◽  
Acyl Radicals ◽  
Benzyl Radicals ◽  
Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

Computationally Augmented Retrosynthesis: Total Synthesis of Paspaline A and Emindole PB

2018 ◽  
Author(s):  
Timothy Newhouse ◽  
Daria E. Kim ◽  
Joshua E. Zweig
Keyword(s):  
Chemical Synthesis ◽  
Total Synthesis ◽  
Small Molecules ◽  
First Principles ◽  
Quantum Chemical ◽  
Computational Analysis ◽  
Empirical Evaluation ◽  
Synthetic Strategy ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions

The diverse molecular architectures of terpene natural products are assembled by exquisite enzyme-catalyzed reactions. Successful recapitulation of these transformations using chemical synthesis is hard to predict from first principles and therefore challenging to execute. A means of evaluating the feasibility of such chemical reactions would greatly enable the development of concise syntheses of complex small molecules. Herein, we report the computational analysis of the energetic favorability of a key bio-inspired transformation, which we use to inform our synthetic strategy. This approach was applied to synthesize two constituents of the historically challenging indole diterpenoid class, resulting in a concise route to (–)-paspaline A in 9 steps from commercially available materials and the first pathway to and structural confirmation of emindole PB in 13 steps. This work highlights how traditional retrosynthetic design can be augmented with quantum chemical calculations to reveal energetically feasible synthetic disconnections, minimizing time-consuming and expensive empirical evaluation.

Synthesis of Elaborate Benzofuran-2-Carboxamide Derivatives Through a Combination of 8-Aminoquinoline Directed C–H Arylations and Transamidations

2019 ◽  
Author(s):  
Michael Oschmann ◽  
Linus Johansson Holm ◽  
Oscar Verho
Keyword(s):  
Small Molecule ◽  
High Efficiency ◽  
Synthetic Strategy ◽  
Small Molecule Screening ◽  
Physiological Properties ◽  
Wide Range ◽  
Directing Group ◽  
Synthetic Sequence

Benzofurans are everywhere in nature and they have been extensively studied by medicinal chemists over the years because of their chemotherapeutic and physiological properties. Herein, we describe a strategy that can be used to access elaborate benzo-2-carboxamide derivatives, which involves a synthetic sequence of 8-aminoquinoline directed C–H arylations followed by transamidations. For the directed C–H arylations, Pd catalysis was used to install a wide range of aryl and heteroaryl substituents at the C3 position of the benzofuran scaffold in high efficiency. Directing group cleavage and further diversification of the C3-arylated benzofuran products were then achieved in a single synthetic operation through the utilization of a two-step transamidation protocol. By bocylating the 8-aminoquinoline amide moiety of these products, it proved possible to activate them towards aminolysis with different amine nucleophiles. Interestingly, this aminolysis reaction was found to proceed efficiently without the need of any additional catalyst or additive. Given the high efficiency and modularity of this synthetic strategy, it constitute a very attractive approach for generating structurally-diverse collections of benzofuran derivatives for small molecule screening.

Access to Fe(II) Bis(σ-B-H) Aminoborane Complexes via Protonation of a Borohydride Complex and Dehydrogenation of Amine-Boranes

2019 ◽  
Author(s):  
Nikolaus Gorgas ◽  
Berthold Stöger ◽  
Luis F. Veiros ◽  
Karl Kirchner
Keyword(s):  
Structural Characterization ◽  
Ammonium Salts ◽  
Iron Based ◽  
Amine Boranes

We report on the first synthesis and structural characterization of the iron based aminoborane complexes. These species are formed upon protonation of a borohydride complex by ammonium salts.<br>

(±)-3,5-Bis(substitutedmethyl)pyrrolidines: Application to the Synthesis of Analogues of glycine-L-proline-L-glutamic Acid (GPE)

2018 ◽  
Vol 15 (2) ◽  
pp. 230-236 ◽  
Author(s):  
Joana Ferreira da Costa ◽  
Xerardo Garcia-Mera ◽  
David Silva Poceiro ◽  
Olga Caamano
Keyword(s):  
Therapeutic Strategy ◽  
Dimethyl Ester ◽  
Neuronal Loss ◽  
New Drugs ◽  
Ester Hydrochloride ◽  
1H And 13C Nmr ◽  
Survival Factor ◽  
Synthetic Strategy ◽  
Β Amyloid ◽  
Structural Simplicity

Backiground: Alzheimer's disease is a fatal, complex, neurodegenerative disease over 46 million people live with dementia in the world characterized by the presence of plaques containing β-amyloid and neuronal loss. The GPE acts as a survival factor against β-amyloid insult in brain and suggests a possible new therapeutic strategy for the treatment of Central Nervous System injuries and neurodegenerative disorders. The structural simplicity of GPE makes it a suitable lead molecule for the development of new drugs that to cross the blood-brain barrier. Objective: With these aims in mind, we embarked on a synthetic program focused on the modification of the Lproline residue of GPE in order to investigate its importance on the neuroprotective activities. Method: The general synthetic strategy involved the preparation of several modified proline residues, which were subsequently coupled to N-Boc-glycine-OH and glutamic dimethyl ester hydrochloride. Results: the mixture of compounds 11 was obtained in good yields (72%) under these conditions, and this was readily separated by column chromatography and the components were identified by 1H and 13C NMR spectral, as well as by its EI HRMS. Conclusion: Compound (±)-8 was coupled with L-glutamic dimethyl ester hydrochloride gave a mixture of dipeptides 9a and 9b in a satisfactory yield. The use of T3P as coupling agent of the mixture 10a and 10b with Boc-glycine provided a new analogue of GPE, tripeptide 11, obtained with an overall yield of 65% from (±)-1.

Application of Nitrogen Heterocyclic Carbenes in Organocatalysis

2020 ◽  
Vol 09 ◽  
Author(s):  
Minita Ojha ◽  
R. K. Bansal
Keyword(s):  
Asymmetric Catalysis ◽  
Building Blocks ◽  
Structural Features ◽  
Heterocyclic Carbenes ◽  
Stetter Reaction ◽  
Metal Pollutants ◽  
Synthetic Strategy ◽  
Wide Range ◽  
Benzoin Condensation ◽  
Nitrogen Heterocyclic

Background: During the last two decades, horizon of research in the field of Nitrogen Heterocyclic Carbenes (NHC) has widened remarkably. NHCs have emerged as ubiquitous species having applications in a broad range of fields, including organocatalysis and organometallic chemistry. The NHC-induced non-asymmetric catalysis has turned out to be a really fruitful area of research in recent years. Methods: By manipulating structural features and selecting appropriate substituent groups, it has been possible to control the kinetic and thermodynamic stability of a wide range of NHCs, which can be tolerant to a variety of functional groups and can be used under mild conditions. NHCs are produced by different methods, such as deprotonation of Nalkylhetrocyclic salt, transmetallation, decarboxylation and electrochemical reduction. Results: The NHCs have been used successfully as catalysts for a wide range of reactions making a large number of building blocks and other useful compounds accessible. Some of these reactions are: benzoin condensation, Stetter reaction, Michael reaction, esterification, activation of esters, activation of isocyanides, polymerization, different cycloaddition reactions, isomerization, etc. The present review includes all these examples published during the last 10 years, i.e. from 2010 till date. Conclusion: The NHCs have emerged as versatile and powerful organocatalysts in synthetic organic chemistry. They provide the synthetic strategy which does not burden the environment with metal pollutants and thus fit in the Green Chemistry.

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