Enantioselective construction of six- and seven-membered triorgano-substituted silicon-stereogenic heterocycles

AbstractThe exploitation of chirality at silicon in asymmetric catalysis is one of the most intriguing and challenging tasks in synthetic chemistry. In particular, construction of enantioenriched mediem-sized silicon-stereogenic heterocycles is highly attractive, given the increasing demand for the synthesis of novel functional-materials-oriented silicon-bridged compounds. Here, we report a rhodium-catalyzed enantioselective construction of six- and seven-membered triorgano-substituted silicon-stereogenic heterocycles. This process undergoes a direct dehydrogenative C−H silylation, giving access to a wide range of triorgano-substituted silicon-stereogenic heterocycles in good to excellent yields and enantioselectivities, that significantly enlarge the chemical space of the silicon-centered chiral molecules. Further elaboration of the chiral monohydrosilane product delivers various corresponding tetraorgano-substituted silicon-stereogenic heterocycles without the loss of enantiopurity. These silicon-bridged heterocycles exhibit bright blue fluorescence, which would have potential application prospects in organic optoelectronic materials.

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Enantioselective Construction of Six- and Seven-Membered Triorgano-Substituted Silicon-Stereogenic Heterocycles

10.21203/rs.3.rs-108883/v1 ◽

2020 ◽

Author(s):

Chuan He ◽

Shuyou Chen ◽

Delong Mu ◽

Pei-Lin Mai ◽

Jie Ke

Keyword(s):

Potential Application ◽

Chemical Space ◽

Optoelectronic Materials ◽

Chiral Molecules ◽

Blue Fluorescence ◽

Wide Range ◽

Organic Optoelectronic ◽

Bright Blue Fluorescence ◽

Bright Blue ◽

Application Prospects

Abstract A rhodium-catalyzed enantioselective construction of six- and seven-membered triorgano-substituted silicon-stereogenic heterocycles is developed. This process undergoes a direct dehydrogenative C−H silylation, giving access to a wide range of novel triorgano-substituted silicon-stereogenic heterocycles in good to excellent yields and enantioselectivities, that significantly enlarged the chemical space of the silicon-centered chiral molecules. Further elaboration of the chiral monohydrosilane product delivered various corresponding tetraorgano-substituted silicon-stereogenic heterocycles without the loss of enantiopurity. These novel silicon-bridged heterocycles exhibit bright blue fluorescence, which would have potential application prospects in organic optoelectronic materials.

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Metal-, and Organocatalyst-Free One-Pot Assembly of Chiral Aza-Tricyclic Molecules: Creating Six Contiguous Stereocenters from 2-D-Structures and an Amino Acid

10.26434/chemrxiv.12757943.v1 ◽

2020 ◽

Author(s):

Dung Do

Keyword(s):

Amino Acid ◽

Chemical Space ◽

Structural Diversity ◽

Therapeutic Agents ◽

Chiral Molecules ◽

One Pot ◽

Complex Molecules ◽

Chiral Catalyst ◽

Chiral Complex ◽

Free Process

Chiral molecules with their defined 3-D structures are of paramount importance for the study of chemical biology and drug discovery. Having rich structural diversity and unique stereoisomerism, chiral molecules offer a large chemical space that can be explored for the design of new therapeutic agents.1 Practically, chiral architectures are usually prepared from organometallic and organocatalytic processes where a transition metal or an organocatalyst is tailor-made for desired reactions. As a result, developing a method that enables rapid assembly of chiral complex molecules under metal- and organocatalyst-free condition represents a daunting challenge. Here we developed a straightforward route to create a chiral 3-D structure from 2-D structures and an amino acid without any chiral catalyst. The center of this research is the design of a <a>special chiral spiroimidazolidinone cyclohexadienone intermediate</a>, a merger of a chiral reactive substrate with multiple nucleophillic/electrophillic sites and a transient organocatalyst. <a>This unique substrate-catalyst (“subcatalyst”) dual role of the intermediate enhances </a><a>the coordinational proximity of the chiral substrate and catalyst</a> in the key Aza-Michael/Michael cascade resulting in a substantial steric discrimination and an excellent overall diastereoselectivity. Whereas the “subcatalyst” (hidden catalyst) is not present in the reaction’s initial components, which renders a chiral catalyst-free process, it is strategically produced to promote sequential self-catalyzed reactions. The success of this methodology will pave the way for many efficient preparations of chiral complex molecules and aid for the quest to create next generation of therapeutic agents.

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General Cyclopropane Assembly via Enantioselective Redox-Active Carbene Transfer to Aliphatic Olefins

10.26434/chemrxiv.7436795 ◽

2018 ◽

Author(s):

Marc Montesinos-Magraner ◽

Matteo Costantini ◽

Rodrigo Ramirez-Contreras ◽

Michael E. Muratore ◽

Magnus J. Johansson ◽

...

Keyword(s):

Total Synthesis ◽

Asymmetric Synthesis ◽

Chemical Space ◽

Synthetic Approach ◽

Asymmetric Cyclopropanation ◽

Redox Active ◽

Wide Range ◽

Leaving Group ◽

Stereoelectronic Properties ◽

Carbene Transfer

Asymmetric cyclopropane synthesis currently requires bespoke strategies, methods, substrates and reagents, even when targeting similar compounds. This limits the speed and chemical space available for discovery campaigns. Here we introduce a practical and versatile diazocompound, and we demonstrate its performance in the first unified asymmetric synthesis of functionalized cyclopropanes. We found that the redox-active leaving group in this reagent enhances the reactivity and selectivity of geminal carbene transfer. This effect enabled the asymmetric cyclopropanation of a wide range of olefins including unactivated aliphatic alkenes, enabling the 3-step total synthesis of (–)-dictyopterene A. This unified synthetic approach delivers high enantioselectivities that are independent of the stereoelectronic properties of the functional groups transferred. Our results demonstrate that orthogonally-differentiated diazocompounds are viable and advantageous equivalents of single-carbon chirons.

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Application of Nitrogen Heterocyclic Carbenes in Organocatalysis

Current Catalysis ◽

10.2174/2211544709999201201120617 ◽

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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Recent trends in smartphone-based detection for biomedical applications: a review

Analytical and Bioanalytical Chemistry ◽

10.1007/s00216-021-03184-z ◽

2021 ◽

Vol 413 (9) ◽

pp. 2389-2406 ◽

Cited By ~ 1

Author(s):

Soumyabrata Banik ◽

Sindhoora Kaniyala Melanthota ◽

Arbaaz ◽

Joel Markus Vaz ◽

Vishak Madhwaraj Kadambalithaya ◽

...

Keyword(s):

Biomedical Applications ◽

Histopathological Examination ◽

Dark Field ◽

Portable Devices ◽

Food Technology ◽

Wide Range ◽

Technological Interventions ◽

Recent Trends ◽

Increasing Demand

AbstractSmartphone-based imaging devices (SIDs) have shown to be versatile and have a wide range of biomedical applications. With the increasing demand for high-quality medical services, technological interventions such as portable devices that can be used in remote and resource-less conditions and have an impact on quantity and quality of care. Additionally, smartphone-based devices have shown their application in the field of teleimaging, food technology, education, etc. Depending on the application and imaging capability required, the optical arrangement of the SID varies which enables them to be used in multiple setups like bright-field, fluorescence, dark-field, and multiple arrays with certain changes in their optics and illumination. This comprehensive review discusses the numerous applications and development of SIDs towards histopathological examination, detection of bacteria and viruses, food technology, and routine diagnosis. Smartphone-based devices are complemented with deep learning methods to further increase the efficiency of the devices.

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Characterizing Bacterial Cellulose Produced byKomagataeibacter sucrofermentans H-110 on Molasses Medium and Obtaining a Biocomposite Based on It for the Adsorption of Fluoride

Polymers ◽

10.3390/polym13091422 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1422

Author(s):

Viktor V. Revin ◽

Alexander V. Dolganov ◽

Elena V. Liyaskina ◽

Natalia B. Nazarova ◽

Anastasia V. Balandina ◽

...

Keyword(s):

Composite Material ◽

Adsorption Capacity ◽

Bacterial Cellulose ◽

Functional Materials ◽

Degree Of Crystallinity ◽

Maximum Adsorption Capacity ◽

Fluoride Ions ◽

Sorption Ability ◽

Wide Range ◽

Biocomposite Material

Currently, there is an increased demand for biodegradable materials in society due to growing environmental problems. Special attention is paid to bacterial cellulose, which, due to its unique properties, has great prospects for obtaining functional materials for a wide range of applications, including adsorbents. In this regard, the aim of this study was to obtain a biocomposite material with adsorption properties in relation to fluoride ions based on bacterial cellulose using a highly productive strain of Komagataeibacter sucrofermentans H-110 on molasses medium. Films of bacterial cellulose were obtained. Their structure and properties were investigated by FTIR spectroscopy, NMR, atomic force microscopy, scanning electron microscopy, and X-ray structural analysis. The results show that the fiber thickness of the bacterial cellulose formed by the K. sucrofermentans H-110 strain on molasses medium was 60–90 nm. The degree of crystallinity of bacterial cellulose formed on the medium was higher than on standard Hestrin and Schramm medium and amounted to 83.02%. A new biocomposite material was obtained based on bacterial cellulose chemically immobilized on its surface using atomic-layer deposition of nanosized aluminum oxide films. The composite material has high sorption ability to remove fluoride ions from an aqueous medium. The maximum adsorption capacity of the composite is 80.1 mg/g (F/composite). The obtained composite material has the highest adsorption capacity of fluoride from water in comparison with other sorbents. The results prove the potential of bacterial cellulose-based biocomposites as highly effective sorbents for fluoride.

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Regioselective Functionalization of N-Fused Heteroaromatics via FeCl3-Catalyzed Nucleophilic Addition to Activated N-Heterocycles

Synthesis ◽

10.1055/s-0040-1705985 ◽

2020 ◽

Author(s):

Ikyon Kim ◽

Sung June Kim ◽

Sunhee Lee

Keyword(s):

Aromatic Compounds ◽

Nucleophilic Addition ◽

Chemical Space ◽

Wide Range ◽

Regioselective Functionalization

AbstractBroadening of nitrogen-fused heteroaromatic chemical space such as indolizine and pyrrolo[1,2-a]pyrazine was achieved via FeCl3-catalyzed nucleophilic addition of these N-fused aromatic compounds to a wide range of azolinium systems generated in situ, leading to novel N-fused heteroaromatic scaffolds with dearomatized N-heterocyclic substituents regioselectively. Nucleophilic addition of indolizines and pyrrolo[1,2-a]pyrazines mainly occurred at the C1 position of the isoquinoliniums and at the C4 site of the quinoliniums.

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Photocatalytic three-component asymmetric sulfonylation via direct C(sp3)-H functionalization

Nature Communications ◽

10.1038/s41467-021-22690-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Shi Cao ◽

Wei Hong ◽

Ziqi Ye ◽

Lei Gong

Keyword(s):

Asymmetric Catalysis ◽

Organic Synthesis ◽

Photochemical Reaction ◽

Low Cost ◽

Bioactive Molecules ◽

Atom Economy ◽

Mild Conditions ◽

Wide Range ◽

Unsaturated Carbonyl Compound ◽

Direct Functionalization

AbstractThe direct and selective C(sp3)-H functionalization of cycloalkanes and alkanes is a highly useful process in organic synthesis owing to the low-cost starting materials, the high step and atom economy. Its application to asymmetric catalysis, however, has been scarcely explored. Herein, we disclose our effort toward this goal by incorporation of dual asymmetric photocatalysis by a chiral nickel catalyst and a commercially available organophotocatalyst with a radical relay strategy through sulfur dioxide insertion. Such design leads to the development of three-component asymmetric sulfonylation involving direct functionalization of cycloalkanes, alkanes, toluene derivatives or ethers. The photochemical reaction of a C(sp3)-H precursor, a SO2 surrogate and a common α,β-unsaturated carbonyl compound proceeds smoothly under mild conditions, delivering a wide range of biologically interesting α-C chiral sulfones with high regio- and enantioselectivity (>50 examples, up to >50:1 rr and 95% ee). This method is applicable to late-stage functionalization of bioactive molecules, and provides an appealing access to enantioenriched compounds starting from the abundant hydrocarbon compounds.

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Advanced Functional Materials Based on Nanocellulose for Pharmaceutical/Medical Applications

Pharmaceutics ◽

10.3390/pharmaceutics13081125 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1125

Author(s):

Raluca Nicu ◽

Florin Ciolacu ◽

Diana E. Ciolacu

Keyword(s):

Rapid Development ◽

Cellulose Nanofibrils ◽

Functional Materials ◽

Medical Applications ◽

Bacterial Nanocellulose ◽

Green Materials ◽

Wide Range ◽

In Vivo Cytotoxicity

Nanocelluloses (NCs), with their remarkable characteristics, have proven to be one of the most promising “green” materials of our times and have received special attention from researchers in nanomaterials. A diversity of new functional materials with a wide range of biomedical applications has been designed based on the most desirable properties of NCs, such as biocompatibility, biodegradability, and their special physicochemical properties. In this context and under the pressure of rapid development of this field, it is imperative to synthesize the successes and the new requirements in a comprehensive review. The first part of this work provides a brief review of the characteristics of the NCs (cellulose nanocrystals—CNC, cellulose nanofibrils—CNF, and bacterial nanocellulose—BNC), as well as of the main functional materials based on NCs (hydrogels, nanogels, and nanocomposites). The second part presents an extensive review of research over the past five years on promising pharmaceutical and medical applications of nanocellulose-based materials, which have been discussed in three important areas: drug-delivery systems, materials for wound-healing applications, as well as tissue engineering. Finally, an in-depth assessment of the in vitro and in vivo cytotoxicity of NCs-based materials, as well as the challenges related to their biodegradability, is performed.

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