scholarly journals Functional group diversity by ruthenium-catalyzed olefin cross-metathesis

2002 ◽  
Vol 74 (1) ◽  
pp. 7-10 ◽  
Author(s):  
F. Dean Toste ◽  
Arnab K. Chatterjee ◽  
Robert H. Grubbs
Keyword(s):  
Functional Groups ◽  
Functional Group ◽  
Chiral Ligands ◽  
Cross Metathesis ◽  
Wide Range ◽  
Group Diversity ◽  
High Degree

Ruthenium-catalyzed olefin cross-metathesis tolerates a wide range of functional groups, including phosphine-boranes, sulfides, amines, phenols, and oxazolines. The high functional group tolerance allows for the use of an olefin as a linchpin for the synthesis of a variety of bi-, tri-, and tetradentate chiral ligands with a high degree of functional group diversity.

Diversifying Polyhydroxyalkanoates – End-Group and Side-Chain Functionality

2017 ◽  
Vol 14 (6) ◽  
pp. 757-767 ◽  
Author(s):  
Michal Michalak ◽  
Iwona Kwiecien ◽  
Michal Kwiecien ◽  
Grazyna Adamus ◽  
Karin Odelius ◽  
...  
Keyword(s):  
Functional Groups ◽  
Polymer Chain ◽  
Ring Opening ◽  
Functional Group ◽  
Side Chain ◽  
Natural Origin ◽  
Polymer Formation ◽  
End Groups ◽  
Group Diversity ◽  
End Group

Background: Polyhydroxyalkanoates (PHAs) are a natural origin biodegradable polyesters consisted of various 3- and 4-hydroxyacid derived repeating units produced by microorganisms as energy storage. PHAs have been intensively studied due to their biodegradability and biocompatibility enabling their use both in packaging and agriculture as well as in medicine and pharmacy. PHAs obtained via biotechnological routes can possess various functional groups in their side chains. However, the diversity in their functionality is limited due to issues of conservation of functional groups during the polymer formation. Objective: The review focuses on recent progress in the area of synthesis of PHAs functionalized with various reactive as well as bioactive end and side groups. Conclusion: A potent route to resolve the problem of functional group diversity in natural origin PHAs involves post-polymerization modification, where the desired side groups can be created. On the contrary, synthetically produced PHA analogs obtained directly via ring-opening polymerization of β-lactones offer various functionalities at different position throughout the polymer chain. The desired α- and ω-end groups can be introduced into the polymer chain using specific polymerization, initiation or termination strategies, respectively. The preferred side chain functionality is obtained by choosing the appropriate β-lactone monomers bearing respective functional groups. All functional groups may also be subjected to additional chemical modification. The degradation of PHA as a method for producing functional polymers as well as their possible further applications are also discussed.

scholarly journals Effects of Oxygenated Acids on Graphene Oxide: The Source of Oxygen-Containing Functional Group

2021 ◽  
Vol 9 ◽  
Author(s):  
Xinghua Zhu ◽  
Yuanpu Xu ◽  
Zhibin Lu ◽  
Qunji Xue
Keyword(s):  
Graphene Oxide ◽  
Functional Groups ◽  
First Principles ◽  
Large Scale ◽  
Functional Group ◽  
Phase Method ◽  
Industrial Synthesis ◽  
Liquid Phase Method ◽  
Wales Defect ◽  
Wide Range

Graphene oxide is an important member of the graphene family which has a wide range of applications. The chemical method, especially the liquid phase method, is one of the most common and important methods for its preparation. However, the complex solution environment not only gives them rich structure, but also brings great challenges for its large-scale industrial synthesis. In order to better realize its industrial application, it is important to understand its structure, such as the source of oxygen-containing functional groups. Here we studied the contribution of four oxygenated acids to oxygen-containing functional groups in Hummers’ method using first principles. We found that the permanganic acid molecules that exist instantaneously due to energy fluctuations can be the source of oxygen-containing functional group. In addition, Stone-Wales defect have a certain effect on the formation of oxygen-containing functional groups, but this effect is not as good as that of solvation effect. This work provides a guide for exploring the source of oxygen-containing functional groups on graphene oxide.

Understanding Conformational Entropy in Small Molecules

2020 ◽  
Author(s):  
Lucian Chan ◽  
Garrett Morris ◽  
Geoffrey Hutchison
Keyword(s):  
Small Molecules ◽  
Degrees Of Freedom ◽  
Absolute Error ◽  
Low Energy ◽  
Standard Entropy ◽  
Free Energies ◽  
Conformational Entropy ◽  
Wide Range ◽  
High Degree ◽  
Empirical Corrections

The calculation of the entropy of flexible molecules can be challenging, since the number of possible conformers grows exponentially with molecule size and many low-energy conformers may be thermally accessible. Different methods have been proposed to approximate the contribution of conformational entropy to the molecular standard entropy, including performing thermochemistry calculations with all possible stable conformations, and developing empirical corrections from experimental data. We have performed conformer sampling on over 120,000 small molecules generating some 12 million conformers, to develop models to predict conformational entropy across a wide range of molecules. Using insight into the nature of conformational disorder, our cross-validated physically-motivated statistical model can outperform common machine learning and deep learning methods, with a mean absolute error ≈4.8 J/mol•K, or under 0.4 kcal/mol at 300 K. Beyond predicting molecular entropies and free energies, the model implies a high degree of correlation between torsions in most molecules, often as- sumed to be independent. While individual dihedral rotations may have low energetic barriers, the shape and chemical functionality of most molecules necessarily correlate their torsional degrees of freedom, and hence restrict the number of low-energy conformations immensely. Our simple models capture these correlations, and advance our understanding of small molecule conformational entropy.

Cerebellotrigeminal Dermal Dysplasia (Gómez-López-Hernández Syndrome)

2018 ◽  
Vol 16 (05) ◽  
pp. 362-368 ◽  
Author(s):  
Federica Sullo ◽  
Agata Polizzi ◽  
Stefano Catanzaro ◽  
Selene Mantegna ◽  
Francesco Lacarrubba ◽  
...  
Keyword(s):  
De Novo ◽  
Chromosomal Rearrangements ◽  
Number Of Patients ◽  
Wide Range ◽  
Visual Problems ◽  
Neurodevelopmental Abnormalities ◽  
Clinical Triad ◽  
High Degree ◽  
Motor Handicap

Cerebellotrigeminal dermal (CTD) dysplasia is a rare neurocutaneous disorder characterized by a triad of symptoms: bilateral parieto-occipital alopecia, facial anesthesia in the trigeminal area, and rhombencephalosynapsis (RES), confirmed by cranial magnetic resonance imaging. CTD dysplasia is also known as Gómez-López-Hernández syndrome. So far, only 35 cases have been described with varying symptomatology. The etiology remains unknown. Either spontaneous dominant mutations or de novo chromosomal rearrangements have been proposed as possible explanations. In addition to its clinical triad of RES, parietal alopecia, and trigeminal anesthesia, CTD dysplasia is associated with a wide range of phenotypic and neurodevelopmental abnormalities.Treatment is symptomatic and includes physical rehabilitation, special education, dental care, and ocular protection against self-induced corneal trauma that causes ulcers and, later, corneal opacification. The prognosis is correlated to the mental development, motor handicap, corneal–facial anesthesia, and visual problems. Follow-up on a large number of patients with CTD dysplasia has never been reported and experience is limited to few cases to date. High degree of suspicion in a child presenting with characteristic alopecia and RES has a great importance in diagnosis of this syndrome.

scholarly journals Thermo- and Photoresponsive Behaviors of Dual-Stimuli-Responsive Organogels Consisting of Homopolymers of Coumarin-Containing Methacrylate

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 329
Author(s):  
Seidai Okada ◽  
Eriko Sato
Keyword(s):  
Functional Group ◽  
Solution Temperature ◽  
Stimuli Responsive ◽  
Critical Solution Temperature ◽  
Equilibrium Degree ◽  
Stimuli Responsive Polymers ◽  
Responsive Polymers ◽  
Dual Functional ◽  
Wide Range ◽  
Increasing Temperature

Coumarin-containing vinyl homopolymers, such as poly(7-methacryloyloxycoumarin) (P1a) and poly(7-(2′-methacryloyloxyethoxy)coumarin) (P1b), show a lower critical solution temperature (LCST) in chloroform, which can be controlled by the [2 + 2] photochemical cycloaddition of the coumarin moiety, and they are recognized as monofunctional dual-stimuli-responsive polymers. A single functional group of monofunctional dual-stimuli-responsive polymers responds to dual stimuli and can be introduced more uniformly and densely than those of dual-functional dual-stimuli-responsive polymers. In this study, considering a wide range of applications, organogels consisting of P1a and P1b, i.e., P1a-gel and P1b-gel, respectively, were synthesized, and their thermo- and photoresponsive behaviors in chloroform were investigated in detail. P1a-gel and P1b-gel in a swollen state (transparent) exhibited phase separation (turbid) through a temperature jump and reached a shrunken state (transparent), i.e., an equilibrium state, over time. Moreover, the equilibrium degree of swelling decreased non-linearly with increasing temperature. Furthermore, different thermoresponsive sites were photopatterned on the organogel through the photodimerization of the coumarin unit. The organogels consisting of homopolymers of coumarin-containing methacrylate exhibited unique thermo- and photoresponsivities and behaved as monofunctional dual-stimuli-responsive organogels.

scholarly journals Controlling Teleportation-Based Locomotion in Virtual Reality with Hand Gestures: A Comparative Evaluation of Two-Handed and One-Handed Techniques

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 715
Author(s):  
Alexander Schäfer ◽  
Gerd Reis ◽  
Didier Stricker
Keyword(s):  
Virtual Reality ◽  
Virtual Worlds ◽  
User Preferences ◽  
Interaction Techniques ◽  
Hand Gestures ◽  
Wide Range ◽  
Effectiveness And Efficiency ◽  
High Degree ◽  
Additional Hardware ◽  
Comprehensive Study

Virtual Reality (VR) technology offers users the possibility to immerse and freely navigate through virtual worlds. An important component for achieving a high degree of immersion in VR is locomotion. Often discussed in the literature, a natural and effective way of controlling locomotion is still a general problem which needs to be solved. Recently, VR headset manufacturers have been integrating more sensors, allowing hand or eye tracking without any additional required equipment. This enables a wide range of application scenarios with natural freehand interaction techniques where no additional hardware is required. This paper focuses on techniques to control teleportation-based locomotion with hand gestures, where users are able to move around in VR using their hands only. With the help of a comprehensive study involving 21 participants, four different techniques are evaluated. The effectiveness and efficiency as well as user preferences of the presented techniques are determined. Two two-handed and two one-handed techniques are evaluated, revealing that it is possible to move comfortable and effectively through virtual worlds with a single hand only.

scholarly journals Modern Synthetic Methods for the Stereoselective Construction of 1,3-Dienes

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 249
Author(s):  
Raquel G. Soengas ◽  
Humberto Rodríguez-Solla
Keyword(s):  
Organic Chemistry ◽  
Natural Products ◽  
Functional Group ◽  
Biological Activities ◽  
Synthetic Methods ◽  
Bond Forming ◽  
Drug Candidates ◽  
The Past ◽  
Wide Range

The 1,3-butadiene motif is widely found in many natural products and drug candidates with relevant biological activities. Moreover, dienes are important targets for synthetic chemists, due to their ability to give access to a wide range of functional group transformations, including a broad range of C-C bond-forming processes. Therefore, the stereoselective preparation of dienes have attracted much attention over the past decades, and the search for new synthetic protocols continues unabated. The aim of this review is to give an overview of the diverse methodologies that have emerged in the last decade, with a focus on the synthetic processes that meet the requirements of efficiency and sustainability of modern organic chemistry.

Preparation of Functionalized Diorganomagnesium Reagents in Toluene via Bromine or Iodine/Magnesium-Exchange Reactions

Synthesis ◽  
2021 ◽  
Author(s):  
Alexandre Desaintjean ◽  
Fanny Danton ◽  
Paul Knochel
Keyword(s):  
Exchange Reaction ◽  
Nitro Group ◽  
General Formula ◽  
Functional Groups ◽  
Exchange Reactions ◽  
Acyl Chlorides ◽  
Aryl Iodides ◽  
Highly Sensitive ◽  
Wide Range ◽  
Magnesium Exchange

A wide range of polyfunctionalized di(hetero)aryl- and dialkenyl-magnesium reagents were prepared in toluene within 10 to 120 min between −78 °C and 25 °C via an I/Mg- or Br/Mg-exchange reaction using reagents of the general formula R2Mg (R = sBu, Mes). Highly sensitive functional groups, such as a triazene or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of various functionalized (hetero)arenes and alkenes derivatives after quenching with several electrophiles including allyl bromides, acyl chlorides, aldehydes, ketones, and aryl iodides.

Nickel-Catalyzed Electronically-Reversed Enantioselective Hydrocarbofunctionalizations of Acrylamides

Synlett ◽  
2021 ◽  
Author(s):  
Lou Shi ◽  
Wei Shu
Keyword(s):  
Nickel Catalyst ◽  
Functional Group ◽  
Optically Active ◽  
Forming Process ◽  
Carbon Bond ◽  
Bond Forming ◽  
Synthetic Strategy ◽  
Carbon Carbon Bond ◽  
Wide Range ◽  
Simple Protocol

Asymmetric hydrocarbofunctionalizations of alkenes has emerged as an efficient synthetic strategy for accessing optically active molecules via carbon-carbon bond-forming process from readily available alkenes and carbo-electrophiles. Herein, we present a summary of the efforts from our group to control the regio- and enantioselectivity of hydrocarbofunctionalizations of electron-deficient alkenes with a nickel catalyst and chiral bisoxazolidine ligand. The reaction undergoes electron-reversed hydrocarbofunctionalizations acrylamides with excellent enantioselectivity. This operationally simple protocol enables the asymmetric hydroalkylation, hydrobenzylation and hydropropargylation of acrylamides. This reaction is useful for preparing a wide range of α-branched chiral amides with broad functional group tolerance.

scholarly journals Resilience of Epiphytic Lichens to Combined Effects of Increasing Nitrogen and Solar Radiation

2021 ◽  
Vol 7 (5) ◽  
pp. 333
Author(s):  
Lourdes Morillas ◽  
Javier Roales ◽  
Cristina Cruz ◽  
Silvana Munzi
Keyword(s):  
Global Change ◽  
Solar Radiation ◽  
Functional Groups ◽  
Physiological Response ◽  
Functional Group ◽  
Environmental Drivers ◽  
Combined Effects ◽  
Environmental Stressor ◽  
Comprehensive Understanding ◽  
Direct Sunlight

Lichens are classified into different functional groups depending on their ecological and physiological response to a given environmental stressor. However, knowledge on lichen response to the synergistic effect of multiple environmental factors is extremely scarce, although vital to get a comprehensive understanding of the effects of global change. We exposed six lichen species belonging to different functional groups to the combined effects of two nitrogen (N) doses and direct sunlight involving both high temperatures and ultraviolet (UV) radiation for 58 days. Irrespective of their functional group, all species showed a homogenous response to N with cumulative, detrimental effects and an inability to recover following sunlight, UV exposure. Moreover, solar radiation made a tolerant species more prone to N pollution’s effects. Our results draw attention to the combined effects of global change and other environmental drivers on canopy defoliation and tree death, with consequences for the protection of ecosystems.

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