Mechanistic study of cobalt(I)-catalyzed asymmetric coupling of ethylene and enynes to functionalized cyclobutanes.

Density functional theory (DFT) calculations have been performed to gain insight into the reaction mechanism of the Co(I)-catalyzed asymmetric [2 + 2] cycloaddition reaction of enyne 1a with ethylene 2 to give the functionalized cyclobutene E-4a possessing a chiral, all-carbon quaternary center in the ring framework (Science, 361, 68-72). This study reveals that the whole catalysis can be characterized via three stages: (i) oxidative dimerization followed by reductive elimination gives the intermediate IM3, (ii) the alkenyl-Co(III) metallacycloheptene IM6 formation with the addition of another equivalent ethylene via an oxidative dimerization process, (iii) ß-Hydrogen elimination and reductive elimination from IM6 to result in the final product E-4a and regenerate the active speices IM1 for the next catalytic cycle. Each stage is kinetically and thermodynamically feasible for experimental realization under mild conditions, and the formation of the alkenyl-Co(III) metallacycloheptene IM6, with a barrier of 27.2 kcal mol-1 (i.e., IM2 → TS4), should be the rate-determining step (RDS) during the whole catalysis. In addition, the origins of enantioselectivity and regioselectivity of the product are discussed.

Linear group 13 E[triple bond, length as m-dash]E triple bonds.

The unexpected linear group 13 E[triple bond, length as m-dash]E triple bonds were herein uncovered with the D3h-symmetry E2M5+ (M = Li, Na, and K) clusters, where the linear M-E[triple bond, length as m-dash]E-M form is perfectly surrounded by M3 motifs. The increasing nonbonded electron density of the heavier main-group elements is the key issue for the trans-bent geometry, and yet it is strongly suppressed in E2M5+, creating two degenerate π bonds and one multi-center σ bond.

Aluminum alkoxy-catalyzed biomass conversion of glucose to 5-hydroxymethylfurfural: Mechanistic study of the cooperative bifunctional catalysis.

Density functional theory calculations were performed to understand the detailed reaction mechanism of aluminum alkoxy-catalyzed conversion of glucose to 5-hydroxymethylfurfural (HMF) using Al(OMe)3 as catalyst. Potential energy surfaces were studied for aggregates formed between the organic compounds and Al(OMe)3 and effects of the medium were considered via continuum solvent models. The reaction takes place via two stages: isomerization from glucose to fructose (stage I) and transformation of fructose to HMF (stage II). Stage II includes three successive dehydrations, which begins with a 1,2-elimination to form an enolate (i.e., B), continues with the formation of the acrolein moiety (i.e., D), and ends with the formation of the furan ring (i.e., HMF). All of these steps are facilitated by aluminum alkoxy catalysis. The highest barriers for stage I and stage II are 23.9 and 31.2 kcal/mol, respectively, and the overall catalytic reaction is highly exothermic. The energetic and geometric results indicate that the catalyzed reaction path has feasible kinetics and thermodynamics and is consistent with the experimental process under high temperature (i.e., 120 °C). Remarkably, the released water molecules in stage II act as the product, reactant, proton shuttle, as well as stabilizer in the conversion of fructose to HMF. The metal-ligand functionality of the Al(OMe)3 catalyst, which combines cooperative Lewis acid and Lewis base properties and thereby enables proton shuttling, plays a crucial role in the overall catalysis and is responsible for the high reactivity. © 2019 Wiley Periodicals, Inc.

Enhanced photocatalytic ammonia oxidation over WO3@TiO2 heterostructures by constructing an interfacial electric field.

WO3 nanorods and xWO3@TiO2 (WO3/TiO2 mass ratio (x) = 1-5) photocatalysts were synthesized using the hydrothermal and sol-gel methods, respectively. The photocatalytic activities of xWO3@TiO2 for NH3 oxidation first increased and then decreased with a rise in TiO2 content. Among them, the heterostructured 3WO3@TiO2 photocatalyst showed the highest NH3 conversion (58 %) under the simulated sunlight irradiation, which was about two times higher than those of WO3 and TiO2. Furthermore, the smallest amounts of by-products (i.e., NO and NO2) were produced over 3WO3@TiO2. The enhancement in photocatalytic performance (i.e., NH3 conversion and N2 selectivity) of 3WO3@TiO2 was mainly attributed to the formed interfacial electric field between WO3 and TiO2, which promoted efficient separation and transfer of photogenerated charge carriers. Based on the results of reactive species trapping and active radical detection, photocatalytic oxidation of NH3 over 3WO3@TiO2 was governed by the photogenerated holes and superoxide radicals. This work combines two strategies of morphological regulation and interfacial electric field construction to simultaneously improve light utilization and photogenerated charge separation efficiency, which promotes the development of full-spectrum photocatalysts for the removal of ammonia.

Human Error Analysis and Modeling of Medication-Related Adverse Events in Taiwan Using the Human Factors Analysis and Classification System and Logistic Regression.

Medical institutions worldwide strive to avoid adverse medical events, including adverse medication-related events. However, studies on the comprehensive analysis of medication-related adverse events are limited. Therefore, we aimed to identify the error factors contributing to medication-related adverse events using the Human Factors Analysis and Classification System (HFACS) and to develop error models through logistic regression. These models calculate the probability of a medication-related adverse event when a healthcare system defect occurs. Seven experts with at least 12 years of work experience (four nurses and three pharmacists) were recruited to analyze thirty-seven medication-related adverse events. The findings indicate that decision errors, physical/mental limitations, failure to correct problems, and organizational processes were the four factors that most frequently contributed to errors at the four levels of the HFACS. Seven error models of two types (error occurrence and error analysis pathways) were established using logistic regression models, and the relative probabilities of failure factor occurrences were calculated. Based on our results, medical staff can use the error models as a new analytical approach to improve and prevent adverse medication events, thereby improving patient safety.

Sinudenoids A-E, C19-Norcembranoid Diterpenes with Unusual Scaffolds from the Soft Coral Sinularia densa.

Five new furanobutenolide-derived C19-norcembranoid diterpenes, sinudenoids A-E (1-5, respectively), were isolated from the soft coral Sinularia densa. Sinudenoid A (1) possesses an uncommon 5/5/11-fused tricyclic ring system. Sinudenoids B-D (2-4, respectively) share the same tetracyclic 5/5/6/6 ring system but represent two kinds of new skeletons. Sinudenoid E (5) is the second compound with the rare 8/8 bicyclic carbon core. A plausible biosynthesis pathway for compounds 1-6 is proposed. Compound 5 exhibits strong anti-inflammatory activity in the zebrafish model.

Correction: Metal-free [3+3] benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates: direct access to functionalized fluorene and fluorenone derivatives.

Correction for 'Metal-free [3+3] benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates: direct access to functionalized fluorene and fluorenone derivatives' by Ya-Sa Xie et al., Chem. Commun., 2020, 56, 1948-1951, DOI: 10.1039/D0CC00143K.

Metal-free [3+3] benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates: direct access to functionalized fluorene and fluorenone derivatives.

An efficient [3+3] benzannulation of Morita-Baylis-Hillman carbonates with 1-indanylidenemalononitrile was achieved under metal-free reaction conditions selectively delivering a wide range of functional multi-substituted fluorene or fluorenone compounds in high yields, respectively (up to 86% yield). Moreover, experiments and quantum chemical calculations were also performed to study the mechanism of the transformation.