scholarly journals Diels–Alder Cycloaddition with CO, CO2, SO2, or N2 Extrusion: A Powerful Tool for Material Chemistry

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 172
Author(s):  
Stanisław Krompiec ◽  
Aneta Kurpanik-Wójcik ◽  
Marek Matussek ◽  
Bogumiła Gołek ◽  
Angelika Mieszczanin ◽  
...  
Keyword(s):  
New Technologies ◽  
Carbon Oxide ◽  
Diels Alder ◽  
Molecular Structures ◽  
Materials Properties ◽  
Material Chemistry ◽  
Current State ◽  
Functionalized Nanomaterials ◽  
Aromatic Systems ◽  
Derivatives Of

Phenyl, naphthyl, polyarylphenyl, coronene, and other aromatic and polyaromatic moieties primarily influence the final materials’ properties. One of the synthetic tools used to implement (hetero)aromatic moieties into final structures is Diels–Alder cycloaddition (DAC), typically combined with Scholl dehydrocondensation. Substituted 2-pyranones, 1,1-dioxothiophenes, and, especially, 1,3-cyclopentadienones are valuable substrates for [4 + 2] cycloaddition, leading to multisubstituted derivatives of benzene, naphthalene, and other aromatics. Cycloadditions of dienes can be carried out with extrusion of carbon dioxide, carbon oxide, or sulphur dioxide. When pyranones, dioxothiophenes, or cyclopentadienones and DA cycloaddition are aided with acetylenes including masked ones, conjugated or isolated diynes, or polyynes and arynes, aromatic systems are obtained. This review covers the development and the current state of knowledge regarding thermal DA cycloaddition of dienes mentioned above and dienophiles leading to (hetero)aromatics via CO, CO2, or SO2 extrusion. Particular attention was paid to the role that introduced aromatic moieties play in designing molecular structures with expected properties. Undoubtedly, the DAC variants described in this review, combined with other modern synthetic tools, constitute a convenient and efficient way of obtaining functionalized nanomaterials, continually showing the potential to impact materials sciences and new technologies in the nearest future.

scholarly journals Hyperbranched Molecular Structures with Potential Antiviral Activity: Derivatives of 5,6-Dihydroxyindole-2-Carboxylic Acid

Molecules ◽  
2006 ◽  
Vol 11 (12) ◽  
pp. 968-977 ◽  
Author(s):  
Mario Sechi ◽  
Fabio Casu ◽  
Ilaria Campesi ◽  
Stefano Fiori ◽  
Alberto Mariani
Keyword(s):  
Carboxylic Acid ◽  
Antiviral Activity ◽  
Molecular Structures ◽  
Derivatives Of

Molding of Three-Dimensional Microcomponents

2006 ◽  
Author(s):  
W. N. P. Hung ◽  
M. M. Agnihotri ◽  
M. Y. Ali ◽  
S. Yuan
Keyword(s):  
Focused Ion Beam ◽  
New Technologies ◽  
Electrical Discharge Machining ◽  
Ion Beam ◽  
Semiconductor Industry ◽  
Three Dimensional ◽  
Cost Effective ◽  
Molecular Structures ◽  
Minimum Size ◽  
Ion Beam Sputtering

Traditional micromanufacturing has been developed for semiconductor industry. Selected micro electrical mechanical systems (MEMS) have been successfully developed and implemented in industry. Since current MEMS are designed for manufacture using microelectronics processes, they are limited to two-dimensional profiles and semiconductor based materials. Such shape and material constraints would exclude many applications that require biocompatibility, dynamic stress, and high ductility. New technologies are sought to fabricate three dimensional microcomponents using robust materials for demanding applications. To be cost effective, such microdevices must be economically mass producible. Molding is one of the promising replication techniques to mass produce components from polymers and polymer-based composites. This paper presents the development of a micromolding process to produce thermoplastic microcomponents. Mold design required precision fitting and was integrated with a vacuum pump to minimize air trap in mold cavities. Nickel and aluminum mold inserts were used for the study; their cavities were fabricated by combinations of available micromachining processes like laser micromachining, micromilling, micro electrical discharge machining, and focused ion beam sputtering. High and low density polyethylene, polystyrene polymers were used for this study. The effects of polymer molecular structures, molding temperature, time, and pressure on molding results were studied. Simulation of stress in the microcomponents, plastic flow in microchannels, and mold defects was performed and compare with experimental data. The research results showed that a microcomponent can be fabricated to the minimum size of 10 ± 1μm (0.0004 inch) with surface roughness <10 nm Rt. Molding of micro-size geartrains and orthopedic meso-size fasteners was completed to illustrate the capability of this process.

scholarly journals Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

2014 ◽  
Vol 10 ◽  
pp. 714-721 ◽  
Author(s):  
Yuta Takano ◽  
Yuki Nagashima ◽  
M Ángeles Herranz ◽  
Nazario Martín ◽  
Takeshi Akasaka
Keyword(s):  
Thermal Stability ◽  
Material Science ◽  
Molecular Structures ◽  
Spectroscopic Methods ◽  
Dynamic Nmr ◽  
The Novel ◽  
Endohedral Metallofullerenes ◽  
Derivatives Of ◽  
Paramagnetic Properties

The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science.

scholarly journals Chitosan Applications on Pharmaceutical Sciences: A Review

2019 ◽  
Vol 9 (3) ◽  
pp. 167-181
Author(s):  
Cintia Alejandra Briones Nieva ◽  
Mercedes Villegas ◽  
Alicia Graciela Cid ◽  
Analía Irma Romero ◽  
José María Bermúdez
Keyword(s):  
New Technologies ◽  
Immunological Response ◽  
Biological Properties ◽  
Future Research ◽  
Pharmaceutical Sciences ◽  
Chemical Derivatization ◽  
Current State ◽  
Pharmaceutical Applications ◽  
Novel Applications ◽  
State Of Art

Background: Chitosan (CS) is a biomaterial derived from chitin, known for its excellent biological properties. One of the most interesting features of CS is its potential for chemical derivatization, which makes it a versatile material and allows to expand its applications. In the last years, the interest on this polymer and its pharmaceutical applications has notably increased. This biopolymer is being widely studied for its interesting properties, such as bioadhesion, antimicrobial activity, biocompatibility, and biodegradability. Other promising properties of CS include its modulation of immunological response, hemostasis, and wound and bone healing activity. Objective: In this work, a critical review is performed covering its conventional and novel applications, specially focused on pharmaceutical area, providing a clear picture of the current state of art to serve as a basis to direct future research in this field. Conclusion: Despite all the qualities of this polymer, there are only few CS-based products in the market, so it is a priority to enhance the research to develop new technologies and CS-based systems to enforce this biopolymer in the industry.

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