A novel and unusual palladium‐catalyzed 4+2 annulation of cyclopropenes with benzosilacyclobutanes is reported. This reaction occurred through chemoselective Si−C(sp2) bond activation in synergy with ...ring expansion/insertion of cyclopropenes to form new C(sp2)−C(sp3) and Si−C(sp3) bonds. An array of previously elusive bicyclic skeleton with high strain, silabicyclo4.1.0heptanes, were formed in good yields with excellent diastereoselectivity under mild conditions. An asymmetric version of the reaction with a chiral phosphoramidite ligand furnished a variety of chiral bicyclic silaheterocycle derivatives with good enantioselectivity (up to 95.5:4.5 er). Owing to the mild reaction conditions, the good stereoselectivity profile, and the ready availability of the functionalized precursors, this process constitutes a useful and straightforward strategy for the synthesis of densely functionalized silacycles.
When Si−C meets C=C bond activation: Cyclopropenes were functionalized stereoselectively with benzosilacyclobutanes by palladium‐catalyzed Si−C(sp2) bond activation and a ring‐expansion/4+2 annulation sequence to form new C(sp2)−C(sp3) and Si−C(sp3) bonds of silabicyclo4.1.0heptanes. The transformation provided an array of these previously elusive highly strained bicyclic skeletons in good yields with high selectivity (see scheme).
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•A comprehensive timeline of catalytic carbonylation of formic acid and formaldehyde is presented.•The catalytic synthesis of various carbonyl compounds by transition-metal complexes ...is discussed.•The catalytic application of formic acid and formaldehyde as non-gaseous C1 source are highlighted.•The mechanistic rationale of transfer carbonylation with HCOOH and HCHO is outlined.
While carbon monoxide (CO) gas has been extensively applied in the bulk chemical industry, its intrinsic properties such as high toxicity, flammability, and special equipment requirement for handling, limit its utilization in organic synthesis, fine chemical industry and academia. Recently, considerable effort has been devoted to the development of CO surrogates to avoid the direct use of carbon monoxide gas. Among the various CO surrogates, formic acid and formaldehyde, have a broad range of applications in organic synthesis. The direct carbonylation with formic acid (HCOOH) and formaldehyde (HCHO) represents one of the most atom-economical substitutes owing to their high weight percentage of CO. In this review, the potential roles of both formic acid and formaldehyde in transition-metal catalyzed carbonylation reactions are discussed. In order to understand these transfer carbonylation reactions, the mechanistic rationale for representative examples is also provided.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
High‐yield and large‐scale synthesis are highly demanded for the studies of gold nanoclusters. We developed a “cluster from cluster” approach to assemble gold nanoclusters with preformed atomically ...precise Au13 precursors. This facile approach has proved to be very effective in the synthesis of the well‐known magic cluster Au25(SR)18−, which could prepare the target cluster in high yield (overall yield up to ≈100 %) at large scale (gram‐scale based on gold). This method can be applied in the synthesis of 10 Au25 clusters with different R groups. This work presents an important approach that may be extended to high‐yield and large‐scale synthesis of other metal nanoclusters.
A “cluster from cluster” approach was developed to assemble gold nanoclusters via preformed atomically precise Au13 precursors. This facile approach has attractive advantages: very high overall yield (≈100 %), large scale (gram‐scale) and generally applicable in the synthesis of magic cluster Au25 (10 examples).
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•This study aimed to update the former meta-analyses, and give an overview of the evidence from RCTs that focused on the efficacy of CBT for patients with somatoform disorders and medically ...unexplained physical symptoms.•It suggested that CBT is effective for somatoform disorders and MUPS by reducing physical symptoms, anxiety symptoms and depressive symptoms, improving physical functioning. The efficacy of CBT on alleviating somatic symptoms, anxiety and depressive symptoms were sustained on follow-up.•The results of subgroup analysis indicated that CBT was particularly beneficial to reduce the somatic symptoms when the session duration was over50 min, group based, and applied affective and good interpersonal strategies.
This systematic review and meta-analysis aimed to update and give an overview of the evidence from published literature that focused on the efficacy of cognitive behaviour therapy (CBT) in the management of somatoform disorders and medically unexplained physical symptoms (MUPS).
A comprehensive literature search was carried out through an electronic search of various databases on randomized controlled trials (RCTs). Primary outcome was the severity of somatic symptoms. Secondary outcomes were also measured based on severity of anxiety symptoms, severity of depressive symptoms, social functioning, physical functioning, doctor visits and the compliance with CBT, as well as follow-up visits. Effects were summarized by a random effects model using mean differences or odds ratio with 95% confidence intervals (CIs).
A total of 15 RCTs comprising 1671 patients with somatoform disorders or MUPS were enrolled in our systematic review and meta-analysis. The main analysis revealed that CBT could alleviate somatic symptoms: −1.31 (95% CI: −2.23 to −0.39, p = 0.005); anxiety symptoms: -1.89 (95% CI: −2.91 to −0.86; p < 0.001); depressive symptoms: −1.93 (95% CI: −3.56 to −0.31; p = 0.020); improve physical functioning: 4.19 (95% CI: 1.90 to 6.49; p < 0.001). The efficacy of CBT on alleviating somatic symptoms, anxiety and depressive symptoms were sustained on follow-up. CBT may not be effective in reducing the number of doctor visits: −1.23 (95% CI: −2.97 to 0.51; p = 0.166); and improving social functioning: 3.27 (95% CI: −0.08 to 6.63; p = 0.056). The results of subgroup analysis indicated that CBT was particularly beneficial when the duration of session was more than 50 min to reduce the severity of somatic symptoms from pre to post treatment time, when it was group based and applied affective and developed good interpersonal strategy during the treatment. Longer duration and frequency such as more than 10 sessions and 12 weeks treatments had significant effect on reduction of the comorbid symptoms including depression and anxiety, but they may underpin low level of compliance of CBT based treatments.
CBT is effective for the treatment of somatoform disorders and MUPS by reducing physical symptoms, psychological distress and disability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A copper catalyst system derived from TaoPhos and CuF2 was used successfully for catalytic asymmetric Huisgen 3+2 cycloaddition of azides and alkynes to give optically pure products containing ...succinimide‐ and triazole‐substituted quaternary carbon stereogenic centers. The desired products were obtained in good yields (60–80 %) and 85:15 to >99:1 enantiomeric ratio (e.r.) in this click cycloaddition reaction.
Click desymmetrization: A new class of chiral phosphine ligands with multistereogenic centers, the so‐called TaoPhos, has been developed successfully for the catalytic asymmetric Huisgen 3+2 cycloaddition of azides and alkynes, in which the desired products were obtained in good yields with high enantioselectivities (up to 99 % ee; see scheme).
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A palladium-catalyzed asymmetric tandem C–C bond activation/Cacchi reaction between cyclobutanones and o-ethynylanilines was reported. The transient chiral σ-alkylpalladium species generated via ...enantioselective C(sp3)–C(sp2) bond activation of cyclobutanones promotes cyclization of o-ethynylanilines, leading to one-carbon-tethered chiral indanone-substituted indoles. Two C–C bonds and one C–N bond are created with concomitant formation of an all-carbon quaternary stereocenter. Furthermore, a chiral C2-aryl axis can be created in 2,3-disubstituted indole moiety, leading to indanone-substituted indoles with both central and axial stereogenic elements.
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A palladium-catalyzed ketoxime-chelation-assisted enantioselective C-H olefination of 2-arylcyclohex-2-enone oxime ether with a wide range of olefins as coupling partners was developed. Employing ...ketoxime ether as an efficient directing group, a variety of axially chiral vinyl arenes was synthesized by Pd(ii)-catalyzed C-H functionalization with excellent enantioselectivities (96 → 99% ee) under mild conditions.
A cluster‐based luminescent porous metal–organic framework has been constructed through a “cluster linker” approach. The luminescent gold(I) cluster, prefunctionalized with pyrazinyl groups, was used ...as a cluster linker, similar to an organic linker, to connect silver ions in order to form a 3D framework. 1D channels with 1.1 nm diameter were observed in the framework. The cluster with its intrinsic luminescence was incorporated into a porous framework to give a luminescent bifunctional NbO net. This MOF shows solvatochromic behavior, and the interactions between solvent molecules and silver ions inside the channels account for the changes in absorption and emission spectra.
Cluster linker: A luminescent gold(I) cluster prefunctionalized with pyrazinyl groups (left) was used as a cluster linker, similar to an organic linker, to connect silver ions in order to form a 3D framework. The intrinsic luminescence of the cluster was thus introduced into a bifunctional porous framework, which is characterized by an NbO topology and features 1D channels with a diameter of 1.1 nm.
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The Cu(I)-catalyzed azide-alkyne cycloaddition reaction, also known as click chemistry, has become a useful tool for the facile formation of 1,2,3-triazoles. Specifically, the utility of this ...reaction has been demonstrated by the synthesis of structurally diverse bi- and bis-1,2,3-triazoles. The present review focuses on the synthesis of such bi- and bistriazoles and the importance of using copper-promoted click chemistry (CuAAC) for such transformations. In addition, the application of bitriazoles and the related CuAAAC reaction in different fields, including medicinal chemistry, coordination chemistry, biochemistry, and supramolecular chemistry, have been highlighted.
Abstract
The geomorphology of river basin is complex, and its soil sedimentary characteristics are poorly defined. To study the spatial variability of soil structure in different sedimentary ...environments at the basin scale, 356 sets of soil samples were collected from five typical sedimentary environments in the Yellow River Basin and the Haihe River Basin, including the upper and lower reaches of the rivers, mountain-front plains, central alluvial plains and eastern coastal plains. The particle size distribution (PSD) of the soil samples was obtained using a laser particle size analyzer, and the fractal dimension (D) of the soil structure was derived by applying fractal theory. The PSD, D and the correlation between them were analyzed by the Pearson correlation method for typical sedimentary environments in two basins. The results show that: (1) The main soil types in the typical geological environments in the basin are sand, loamy sand, sandy loam, silty loam, and silty soil. The soil particle size in the upper and lower reaches of the rivers was higher than that in the plain areas. (2) In the plane, The D value descended in different regions in the following order: the mountain-front plain > the eastern coastal plain > the upper Yellow River > the central alluvial plain > the lower Yellow River. In the vertical direction for both rivers, the D value showed a decreasing trend with increasing burial depth. (3) The model results showed a cubic polynomial correlation between D values and PSD, which was closely related to the non-uniformity of particle size during sorting and deposition. The soil PSD and fractal characteristics are effective tools for the quantitative evaluation of soil structure in various sedimentary environments in the basin.
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