Valorization of Carbon Dioxide into Oxazolidinones by Reaction with Aziridines

The reduction of carbon dioxide has gained much attention due to increasing environmental concerns about global warming associated with carbon emissions from industrial effluents and public transport etc. In this regard, considerable attention has been devoted to the chemical conversion of carbon dioxide, and its incorporation into synthetic organic molecules under mild and “green” conditions. In recent years, significant effort has been dedicated to studying the fixation of carbon dioxide with aziridines to afford oxazolidinones, which is an environmental friendly and atom economical process. In this review, we discuss the efficiency of different catalytic systems, by comparing and analyzing each reaction parameter such as pressure, temperature, substrate scope and product selectivity

Recent developments in organocatalysed transformations of epoxides and carbon dioxide into cyclic carbonates

This review is focused on the rapidly developing area of organocatalysed cyclic carbonate synthesis. It starts with an introduction to carbon capture and utilisation in general, which introduces the importance of cyclic carbonates. The various mechanisms for cyclic carbonate synthesis are next discussed with a focus on the relative and absolute stereochemical consequences of each mechanism and how this combined with other physical organic chemistry techniques can be used to distinguish between three main mechanistic classes: epoxide activation; carbon dioxide activation and dual activation. Section 2 of the review then discusses recently reported homogeneous organocatalysed systems whilst section 3 surveys recently reported heterogeneous catalyst systems. For each catalyst system, the mechanism of action is discussed with reference to the mechanisms introduced at the start of the review and key parameters such as the optimal temperature, pressure and catalyst loading are given combined with information on substrate scope and yields. This allows the various catalysts to be critically compared on the basis of whichever parameter(s) are of most significance to the reader. A Final Thoughts/Perspective section focusses on the limitations of the use of turnover frequency and turnover number to compare catalysts in this reaction and makes the case for authors to use of a wider range of green metrics when reporting new catalysts. Finally, the Conclusions section focuses on future challenges such as the use of biomass derived epoxides, use of impure carbon dioxide and the need to develop new and existing highly active catalysts out of the laboratory and into real world applications

“Making Every Second Count”: Utilizing TikTok and Systems Thinking to Facilitate Scientific Public Engagement and Contextualization of Chemistry at Home

TikTok is a social media video-based phone application which enables creative and engaging videos to be shared on social media platforms worldwide. TikTok has been applied to create fun, exciting, and engaging 15–60 s long chemistry outreach educational videos, to encourage public dissemination of science with a systems thinking approach. With the creation of an online TikTok account called “The Chemistry Collective” by undergraduate students, 16 educational videos were created, with approximately 8,500 views. Upon surveying participants, viewers of these TikTok videos strongly agreed that they had learned something new about chemistry since watching these videos (4.66/5.00) and had an increased interest in chemistry (82.7% agreed). As such, TikTok can be used to enhance public and undergraduate student engagement with chemistry and science education, together with facilitating the ability of the public to understand how chemistry can be fun, can be performed at home, and is part of our daily lives

Spectroscopic characterization and thermal behavior of baru nut and macaw palm vegetable oils and their epoxidized derivatives

The ability to produce new and renewable, epoxidized Brazilian vegetable oils from baru nut (Dipteryx alata Vogel) and macaw palm (Acrocomia aculeata) oil, using a fast and clean heterogeneous catalytic method, was investigated. The Wijs method and Proton Nuclear Magnetic Resonance (1H-NMR) analysis were utilized, and compared to one another, to calculate the iodine value (IV), average number of double bonds (DBaverage) and fatty acid content, and thus degree of epoxidation, for both vegetable oils. This analysis indicated that alkene conversions of >99% and 95.3% were obtained for baru nut oil and macaw palm oil, respectively; which is an excellent result when compared with some works in literature. The epoxidized Baru nut oil is a solid at room temperature, which was related to the percentage of mono-unsaturated fatty acids present in its structure. Epoxide samples were also analyzed via mid-Infrared Spectroscopy and 13C NMR analysis. Thermogravimetry-differential thermal analysis (TG-DTA) was used to determine the thermal stability of these epoxidized oils. Differential Scanning Calorimetry (DSC) also provided information about their crystallization, melting and solid-solid transition processes

Unprecedented reductive cyclisation of salophen ligands to tetrahydroquinoxalines during metal complex formation

The synthesis of novel tetrahydroquinoxalines by a metal induced one–electron reductive cyclisation of salophen ligands was found to occur when a salophen ligand was treated with chromium(II) chloride or decamethylcobaltocen

Structural analysis of five-coordinate aluminium(salen) complexes and its relationship to their catalytic activity

The crystal structure of [Al(tBu-salen)]2O·HCl shows major changes compared to that of [Al(tBu-salen)]2O. The additional proton is localized on the bridging oxygen atom, making the aluminium atoms more electron deficient. As a result, a water molecule coordinates to one of the aluminium atoms, which becomes six-coordinate. This pushes the salen ligand associated with the six-coordinate aluminium ion closer to the other salen ligand and results in the geometry around the five-coordinate aluminium atom becoming more trigonal bipyramidal. These results experimentally mirror the predications of DFT calculations on the interaction of [Al(tBu-salen)]2O and related complexes with carbon dioxide. Variable temperature NMR studies of protonated [Al(tBu-salen)]2O complexes revealed that the structures were dynamic and could be explained on the basis of an intramolecular rearrangement in which the non-salen substituent of a five-coordinate aluminium(tBu-salen) unit migrates from one face of a square based pyramidal structure to the other via the formation of structures with trigonal bipyramidal geometries. Protonated [Al(tBu-salen)]2O complexes were shown to have enhanced Lewis acidity relative to [Al(tBu-salen)]2O, coordinating to water, dioxane and 1,2-epoxyhexane. Coordinated epoxyhexane was activated towards ring-opening, to give various species which remained coordinated to the aluminium centers. The protonated [Al(tBu-salen)]2O complexes catalysed the synthesis of cyclic carbonates from epoxides and carbon dioxide both in the presence and absence of tetrabutylammonium bromide as a nucleophilic cocatalyst. The catalytic activity was principally determined by the nature of the nucleophilic species within the catalyst structure rather than by changes to the Lewis acidity of the metal centers

Diversity aboard a Tudor warship: investigating the origins of the Mary Rose crew using multi-isotope analysis

The great Tudor warship, the Mary Rose, which sank tragically in the Solent in 1545 AD, presents a rare archaeological opportunity to research individuals for whom the precise timing and nature of death are known. A long-standing question surrounds the composition of the Tudor navy and whether the crew were largely British or had more diverse origins. This study takes a multi-isotope approach, combining strontium (87Sr/86Sr), oxygen (δ18O), sulfur (δ34S), carbon (δ13C) and nitrogen (δ15N) isotope analysis of dental samples to reconstruct the childhood diet and origins of eight of the Mary Rose crew. Forensic ancestry estimation was also employed on a subsample. Provenancing isotope data tentatively suggests as many as three of the crew may have originated from warmer, more southerly climates than Britain. Five have isotope values indicative of childhoods spent in western Britain, one of which had cranial morphology suggestive of African ancestry. The general trend of relatively high δ15N and low δ13C values suggests a broadly comparable diet to contemporaneous British and European communities. This multi-isotope approach and the nature of the archaeological context has allowed the reconstruction of the biographies of eight Tudor individuals to a higher resolution than is usually possible

Evaluating the Viability of Successive Ring-Expansions Based on Amino Acid and Hydroxyacid Side-Chain Insertion

The outcome of ring expansion reactions based on amino/hydroxyacid side chain insertion is strongly dependent on ring size. This manuscript, which builds upon our previous work on Successive Ring Expansion (SuRE) methods, details efforts to better define the scope and limitations of these reactions on lactam and β-ketoester ring systems with respect to ring size and additional functionality. The synthetic results provide clear guidelines as to which substrate classes are more likely to be successful and are supported by computational results, using a Density Functional Theory (DFT) approach. Calculating the relative Gibbs free energies of the three isomeric species that are formed reversibly during ring expansion enables the viability of new synthetic reactions to be correctly predicted in most cases. The new synthetic and computational results are expected to support the design of new lactam- and β-ketoester-based ring expansion reactions

Prominent members of the human gut microbiota express endo-acting O-glycanases to initiate mucin breakdown

Epithelial cells that line the gut secrete complex glycoproteins that form a mucus layer to protect the gut wall from enteric pathogens. Here, the authors provide a comprehensive characterisation of endo-acting glycoside hydrolases expressed by mucin-degrading members of the microbiome that are able to cleave the O-glycan chains of a range of different animal and human mucins

Uncovering treatment burden as a key concept for stroke care: a systematic review of qualitative research

<b>Background</b> Patients with chronic disease may experience complicated management plans requiring significant personal investment. This has been termed ‘treatment burden’ and has been associated with unfavourable outcomes. The aim of this systematic review is to examine the qualitative literature on treatment burden in stroke from the patient perspective.<p></p> <b>Methods and findings</b> The search strategy centred on: stroke, treatment burden, patient experience, and qualitative methods. We searched: Scopus, CINAHL, Embase, Medline, and PsycINFO. We tracked references, footnotes, and citations. Restrictions included: English language, date of publication January 2000 until February 2013. Two reviewers independently carried out the following: paper screening, data extraction, and data analysis. Data were analysed using framework synthesis, as informed by Normalization Process Theory. Sixty-nine papers were included. Treatment burden includes: (1) making sense of stroke management and planning care, (2) interacting with others, (3) enacting management strategies, and (4) reflecting on management. Health care is fragmented, with poor communication between patient and health care providers. Patients report inadequate information provision. Inpatient care is unsatisfactory, with a perceived lack of empathy from professionals and a shortage of stimulating activities on the ward. Discharge services are poorly coordinated, and accessing health and social care in the community is difficult. The study has potential limitations because it was restricted to studies published in English only and data from low-income countries were scarce.<p></p> <b>Conclusions</b> Stroke management is extremely demanding for patients, and treatment burden is influenced by micro and macro organisation of health services. Knowledge deficits mean patients are ill equipped to organise their care and develop coping strategies, making adherence less likely. There is a need to transform the approach to care provision so that services are configured to prioritise patient needs rather than those of health care systems