Hasil untuk "Organic chemistry"

Xili Cui, Kai‐Jie Chen, Huabin Xing et al.

Qiang Liu, Lipeng Wu, R. Jackstell et al.

Carbon dioxide is an abundant and easily available source of carbon, produced as a waste product in large quantities worldwide. Here, the authors review recent work on activating and reacting carbon dioxide for use as a building block in organic synthesis. Carbon dioxide exits in the atmosphere and is produced by the combustion of fossil fuels, the fermentation of sugars and the respiration of all living organisms. An active goal in organic synthesis is to take this carbon—trapped in a waste product—and re-use it to build useful chemicals. Recent advances in organometallic chemistry and catalysis provide effective means for the chemical transformation of CO2 and its incorporation into synthetic organic molecules under mild conditions. Such a use of carbon dioxide as a renewable one-carbon (C1) building block in organic synthesis could contribute to a more sustainable use of resources.

Markus J. Kalmutzki, Nikita Hanikel, O. Yaghi

The SBU approach facilitated the development of permanently porous MOFs with unique properties, chemistry, and applications. The secondary building unit (SBU) approach was a turning point in the discovery of permanently porous metal-organic frameworks (MOFs) and in launching the field of reticular chemistry. In contrast to the single-metal nodes known in coordination networks, the polynuclear nature of SBUs allows these structures to serve as rigid, directional, and stable building units in the design of robust crystalline materials with predetermined structures and properties. This concept has also enabled the development of MOFs with ultra-high porosity and structural complexity. The architectural, mechanical, and chemical stability of MOFs imparted by their SBUs also gives rise to unique framework chemistry. All of this chemistry –including ligand, linker, metal exchange, and metallation reactions, as well as precisely controlled formation of ordered vacancies– is carried out with full retention of the MOF structure, crystallinity, and porosity. The unique chemical nature of SBUs makes MOFs useful in many applications including gas and vapor adsorption, separation processes, and SBU-mediated catalysis. In essence, the SBU approach realizes a long-standing dream of scientists by bringing molecular chemistry (both organic and inorganic) to extended solid-state structures. This contribution highlights the importance of the SBUs in the development of MOFs and points to the tremendous potential still to be harnessed.

C. Kappe

M. Dewar

E. Block

G. F.

V. Nesterov, D. Reiter, Prasenjit Bag et al.

Since the discovery of the first stable N-heterocyclic carbene (NHC) in the beginning of the 1990s, these divalent carbon species have become a common and available class of compounds, which have found numerous applications in academic and industrial research. Their important role as two-electron donor ligands, especially in transition metal chemistry and catalysis, is difficult to overestimate. In the past decade, there has been tremendous research attention given to the chemistry of low-coordinate main group element compounds. Significant progress has been achieved in stabilization and isolation of such species as Lewis acid/base adducts with highly tunable NHC ligands. This has allowed investigation of numerous novel types of compounds with unique electronic structures and opened new opportunities in the rational design of novel organic catalysts and materials. This Review gives a general overview of this research, basic synthetic approaches, key features of NHC-main group element adducts, and might be useful for the broad research community.

M. C. Etter

F. Allen, T. P. Singh, Robin Taylor

T. Claridge

Dong-Su Kim, W. Park, C. Jun

Jin‐Bao Peng, H. Geng, Xiao‐Feng Wu

Summary Carbon monoxide is one of the most important C1 molecules in organic chemistry. Many novel procedures for its conversion have been developed, and some have even been industrialized. In this review, we discuss and categorize CO chemistry into four classes: (1) transition-metal-mediated carbonylation, (2) strong-acid-initiated cationic carbonylation, (3) anionic carbonylation, and (4) free-radical carbonylation. Relevant achievements are selected and discussed in detail.

Hao Jiang, Dalal Alezi, M. Eddaoudi

F. Rizzuto, L. S. Krbek, J. Nitschke

Juan B. Pérez-Sánchez, Yunheng Zou, Jorge A. Campos-Gonzalez-Angulo et al.

Quantum chemistry is a foundational enabling tool for the fields of chemistry, materials science, computational biology and others. Despite of its power, the practical application of quantum chemistry simulations remains in the hands of qualified experts due to methodological complexity, software heterogeneity, and the need for informed interpretation of results. To bridge the accessibility gap for these tools and expand their reach to chemists with broader backgrounds, we introduce El Agente Quntur, a hierarchical, multi-agent AI system designed to operate not merely as an automation tool but as a research collaborator for computational quantum chemistry. Quntur was designed following three main strategies: i) elimination of hard-coded procedural policies in favour of reasoning-driven decisions, ii) construction of general and composable actions that facilitate generalization and efficiency, and iii) implementation of guided deep research to integrate abstract quantum-chemical reasoning across subdisciplines and a detailed understanding of the software's internal logic and syntax. Although instantiated in ORCA, these design principles are applicable to research agents more generally and easily expandable to additional quantum chemistry packages and beyond. Quntur supports the full range of calculations available in ORCA 6.0 and reasons over software documentation and scientific literature to plan, execute, adapt, and analyze in silico chemistry experiments following best practices. We discuss the advances and current bottlenecks in agentic systems operating at the research level in computational chemistry, and outline a roadmap toward a fully autonomous end-to-end computational chemistry research agent.

Gözde Bozdal, Şeyma Arıcı Tüfekçi, Büşra Şahin et al.

Volatile organic compounds (VOCs) of essential oils (EOs) and solid phase microextract (SPME) obtained from the flower, leaf, and stem of Epilobium angustifolium L. were analyzed by GC-FID/MS. The EOs and SPMEs consist mainly of monoterpenes and aldehydes, which are major classes of compounds. Limonene was found to be a major compound in flower (HD: 42.9% vs. SPME: 95.5%), in leaf (HD: 60.3% vs. SPME: 4.7%), and in stem (HD: 49.06% vs. SPME: 93.6%). The antimicrobial activity of EOs and the solvent extracts (n-hexane, acetonitrile, and methanol) of E. angustifolium were screened in vitro against nine microorganisms. The EO of the leaf showed the best activity (10.2 µg/mL MIC) against Mycobacterium smegmatis. All the EOs and the solvent extracts gave moderate activity against the Staphylococcus aureus, Bacillus cereus, and M. smegmatis within the range of 10.2-1300.0 µg/mL MIC values. The best antibacterial activity was observed against S. aureus and B. cereus in the n-hexane extract of stem and methanol extract of flower samples.

Yuan Zhang, Yali Jing

Background: Previous studies have suggested that type 2 diabetes mellitus (T2DM) is associated with poor bone health, including osteoporosis (OP) and osteopenia. The ZJU index, a novel calculation that integrates fasting plasma glucose (FPG), body mass index (BMI), triglyceride (TG), and alanine aminotransferase (ALT) to aspartate aminotransferase (AST) ratio, is strongly associated with glucolipid metabolism and insulin resistance (IR). In this study, we explored the association of ZJU with bone mineral density (BMD) and OP/osteopenia, and investigated the predictive effect of ZJU on OP/osteopenia in patients with T2DM. Methods: This cross-sectional study included 496 patients with T2DM aged>50 years. The clinical data were collected and the BMD of femoral neck (FN), left hip (LH), and lumbar spine (LS) were measured. The association between BMDs and ZJU levels was investigated by adjusting for covariates utilizing multiple linear regression analyses. Multivariable logistic regression was constructed to identify independent factors of OP and osteopenia, and receiver operating characteristic (ROC) curves were used to display the diagnostic performance according to the area under the ROC curve (AUC). Results: OP and osteopenia patients showed significantly higher ZJU levels than those with normal BMD in T2DM (39.387 ± 3.558, 38.112 ± 2.552 vs 35.192 ± 2.600, p < 0.001). Spearman's correlation analysis showed that ZJU was significantly negatively correlated with the BMD of FN (r = −0.39, p < 0.001), LH (r = −0.35, p < 0.001), and LS (r = -0.32, p < 0.001). The multiple linear regression indicated a negative association between ZJU and BMD of FN (β = −0.006, p = 0.009), LS (β = -0.155, p = 0.011) after adjusted for covariates. Meanwhile, the results of logistic regression revealed that the ZJU was a contributing factor to osteopenia and OP risk in T2DM individuals aged>50 years (OR 1.446, 95 % CI: 1.087–1.923, p = 0.011; OR 1.878, 95 % CI: 1.218–3.715, p = 0.039, respectively). ZJU provided the AUC value of 0.695 and 0.716 on osteopenia and OP in T2DM, respectively. Conclusions: A high ZJU index was significantly associated with an increasing risk of osteopenia and OP. The ZJU is expected to be a potential index for detecting decreased BMDs in middle-aged and elderly T2DM patients. Early intervention in T2DM patients with increased ZJU may further reduce the incidence of osteopenia and OP, in addition to focusing on independent biomarker in clinical practice.

Marco Conz, Francesca Scognamiglio, Ivan Donati et al.

Long-term solutions for cartilage repair after injury are currently being investigated, with most research aiming to exploit the regenerative and chondrogenic differentiation potential of stem-cell-based spheroids. The incorporation of the bioactive polymer CTL, a lactose-modified chitosan, into spheroids is a strategy to improve cell viability and accelerate type II collagen gene expression. In this work, the role of CTL in influencing the dynamics of spheroid formation and its interplay with cell membrane adhesion molecules (integrins and cadherins) and cytoskeletal components is elucidated. The results indicate that CTL is actively involved in the reorganization of cells into spheroids. An analysis of the effects of physical form of CTL (rehydrated polymer coating or polymer solution) in stimulating peculiar biological responses indicates that CTL matrix in spheroids facilitates an early phase of chondrogenic differentiation. Once the CTL matrix is included in spheroids, there is an increase in COL2A1 gene expression and matrix deposition, regardless of the initial physical form of CTL. Overall, these results contribute to a better understanding of the dynamics of spheroid formation in the presence of the polymer and on its bioactive role in mesenchymal stem cell spheroids.

Huan-Ming Huang, Peter Bellotti, Jiajia Ma et al.