182,042 research outputs found
Photoinduced C—C Bond Cleavage and Oxidation of Cycloketoxime Esters
No full textA novel structural reorganization of cycloketoxime esters beyond the traditional Beckmann rearrangement process has been established to build cyano-containing ketones in the presence of photocatalyst. This novel transformation is remarkable with selective C—C bond cleavage and an oxidation process enabled by DMSO used as the solvent, oxidant, and oxygen source avoiding acid, base and toxic cyanide salts as the cyano source. Further applications in late-stage modification of complex and chiral molecules have also been reported
Pennaticoxita Jiao & Han & Wang & Bu 2016, gen. nov.
No full textGenus Pennaticoxita Jiao & Bu, gen. nov. Type species: Pennaticoxita tauricornuta Jiao & Bu, sp. nov. Diagnosis. The new genus Pennaticoxita gen. nov. is characterized by the uniqueness of gonocoxite having a wing-shaped dorsal lobe in the tribe Brachineurini. And Pennaticoxita gen. nov. and Alatostyla Fedotova & Sidorenko are distinguishable from other genera of subtribe Brachineurina subtrib. nov. by vein R 5 joining vein C at wing apex, vein Cu unforked and hypoproct emarginated forming two distinct lobes, but the new genus differs from Alatostyla by gonostylus normally shaped without lobes, while Alatostyla by gonostylus with a sub-conical basal lobe protruding outwardly. Description. Adult. Palpus with palpiger and 3 segments, last two segments longer than first one (Fig. 1). Antenna with 10 flagellomeres, each with one neck and only one basal node (Fig. 2). Wing (Fig. 3) hyaline, sparsely covered with narrow scales and setose; vein R 1 joining vein C at basal 2/5; vein R 5 bent a little backward, joining vein C at wing apex; vein Cu unforked. Tarsal claw (Fig. 4) toothed on all legs. Male seventh and eighth tergites both reduced to one strongly sclerotized and linear band. Male genitalia (Figs 5–6). Gonocoxite having a wing-shaped dorsal lobe (Fig. 6), and having mediobasal lobe undeveloped, only with several setae inserted in a sub-frustoconical prominence; gonostylus slender and normally shaped; cerci separated to form two broad lobes; hypoproct emarginated forming two digitiform lobes; aedeagus sub-conical, usually with a pair of horn-shaped prominences or other modifications. Female genitalia unknown. Etymology. The genus name means the male gonocoxite having a wing-shaped dorsal lobe.Published as part of Jiao, Kelong, Han, Peijin, Wang, Yuanhong & Bu, Wenjun, 2016, General review of the tribe Brachineurini (Diptera: Cecidomyiidae) with description of Pennaticoxita tauricornuta gen. & sp. nov. from China, pp. 307-314 in Zoological Systematics 41 (3) on pages 310-311, DOI: 10.11865/zs.201633, http://zenodo.org/record/536514
Carbon nanodot decorated graphitic carbon nitride: new insights into the enhanced photocatalytic water splitting from ab initio studies
No full textInterfacing carbon nanodots (C-dots) with graphitic carbon nitride (g-C3N4) produces a metal-free system that has recently demonstrated significant enhancement of photo-catalytic performance for water splitting into hydrogen [Science, 2015, 347, 970-974]. However, the underlying photo-catalytic mechanism is not fully established. Herein, we have carried out density functional theory (DFT) calculations to study the interactions between g-C3N4 and trigonal/hexagonal shaped C-dots. We find that hybrid C-dots/g-C3N4 can form a type-II van der Waals heterojunction, leading to significant reduction of band gap. The C-dot decorated g-C3N4 enhances the separation of photogenerated electron and hole pairs and the composite's visible light response. Interestingly, the band alignment of C-dots and g-C3N4 calculated by the hybrid functional method indicates that C-dots act as a spectral sensitizer in hybrid C-dots/g-C3N4 for water splitting. Our results offer new theoretical insights into this metal-free photocatalyst for water splitting.Guoping Gao, Yan Jiao, Fengxian Ma, Yalong Jiao, Eric Waclawik and Aijun D
Oxygenation via C-H/C-C Bond Activation with Molecular Oxygen
No full textThe selective oxidation of organic molecules is a fundamentally important component of modern synthetic chemistry. In the past decades, direct oxidative C-H and C-C bond functionalization has proved to be one of the most efficient and straightforward methods to synthesize complex products from simple and readily available starting materials. Among these oxidative processes, the use of molecular oxygen as a green and sustainable oxidant has attracted considerable attention because of its highly atom-economical, abundant, and environmentally friendly characteristics. The development of new protocols using molecular oxygen as an ideal oxidant is highly desirable in oxidation chemistry. More importantly, the oxygenation reaction of simple molecules using molecular oxygen as the oxygen source offers one of the most ideal processes for the construction of O-containing compounds. Aerobic oxidation and oxygenation by enzymes, such as monooxygenase, tyrosinase, and dopamine beta-monooxygenase, have been observed in some biological C-H bond hydroxylation processes. Encouraged by these biological transformations, transition-metal- or organocatalyst-catalyzed oxygenation through dioxygen activation has attracted academic and industrial prospects. In this Account, we describe some advances from our group in oxygenation via C-H/C-C bond activation with molecular oxygen as the oxidant and oxygen source for the synthesis of O-containing compounds. Under an atmosphere of O-2 (1 atm) or air (1 atm), we have successfully incorporated one or two 0 atoms from 02 into simple and readily available substrates through C-H, C-C, C=C, and C C bond cleavage by transition-metal catalysis, organocatalysis, and photocatalysis. Moreover, we have devised cyclization reactions with molecular oxygen to construct O-heterocycles. Most of these transformations can tolerate a broad range of functional groups. Furthermore, on the basis of isotope labeling experiments, electron paramagnetic resonance spectral analysis, and other mechanistic studies, we have demonstrated that a single electron transfer process via a carbon radical, peroxide radical, or hydroxyl radical is involved in these aerobic oxidation and oxygenation reactions. These protocols provide new approaches for the green synthesis of various alpha-keto amides, alpha-keto esters, esters, ketones, aldehydes, formamides, 2-oxoacetamidines, 2-(1H)-pyridones, phenols, tertiary alpha-hydroxy carbonyls, p-quinols, beta-azido alcohols, benzyl alcohols, tryptophols, and oxazoles, which have potential applications in the preparation of natural products, bioactive compounds, and functional materials. In most cases, inexpensive and low-toxicity Cu, Fe, Mn, or NHPI was found to be an efficient catalyst for the transformation. The high efficiency, low cost, high oxygen atom economy, broad substrate scope, and practical operation make the developed oxygenation system very attractive and practical. Moreover, the design of new types of molecular-oxygen- or air-based oxidation and oxygenation reactions can be anticipated.National Basic Research Program of China (973 Program) [2015CB856600]; National Natural Science Foundation of China [21325206, 21632001]; National Young Top-Notch Talent Support Program; Peking University Health Science Center [BMU20160541]SCI(E)REVIEW71640-16535
Supporting Information for Jiao et al., 2023.docx
No full textAdditional figures from Jiao, W., Wan, S., Li, Y., Zhao, D., Liu, C., Jin, H., et al. (2023). Global cooling-driven summer monsoon weakening in South China across the Eocene-Oligocene transition.</p
Key to C(2)production: selective C-C coupling for electrochemical CO(2) reduction on copper alloy surfaces
No full textThe C–C coupling kinetic variations are observed on Cu alloys with Pt, Pd, or Au surface sites. The OC–COH coupling is kinetically more favorable than OC–CHO coupling, which originates from increased reactivity of adsorbed *CO species. Linear energy relations for C–C association/dissociation could simplify the energetic evaluation for C2 production.Xing Zhi,, Yan Jiao, Yao Zheng and Shi-Zhang Qia
Dataset for Jiao et al., 2023.xlsx
No full textDataset from Jiao, W., Wan, S., Li, Y., Zhao, D., Liu, C., Jin, H., et al. (2023). Global cooling-driven summer monsoon weakening in South China across the Eocene-Oligocene transition.
The dataset set includes two worksheets in the EXCEL. The first worksheet documents magnetic parameters and diffuse reflectance spectroscopy data. The second one documents the unmixing results of isothermal remanent magnetization acquisition curves.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cortiella C. Norman 1937
No full textKey to the Cortiella species 1 Rays few (3–6); thin pedicels longer than leaves.......................................................................................................... C. yatungense 1 Rays many (more than 6); stout pedicels shorter than leaves or subequal.........................................................................................2 2 Petioles and rachis glabrous or essentially glabrous..........................................................................................................................3 2 Petioles and rachis densely puberulous..............................................................................................................................................4 3 Ultimate leaf segments trind; rays about 10................................................................................................................. C. lamondiana 3 Ultimate leaf segments obovate, 3-lobed, apex rounded; rays 20–30............................................................................ C. caespitosa 4 Dorsal ribs wings broad, slightly narrower than lateral wings, often convoluted and crowded when mature; ultimate leaf segments less than 4 mm; styles (1.5–) 2–3.5 mm after flowering..................................................................................................... C. hookeri 4 Dorsal ribs wings narrow, often poorly developed, much narrower than lateral wings, not convoluted and crowded; ultimate leaf segments usually more than 4 mm; styles 1.75–3 mm after flowering........................................................................... C. cortioidesPublished as part of Deng, Jiao-Jiao, Peng, Chang, Liu, Chang-Kun, Xie, Deng-Feng, Gui, Ling-Jian, Zhou, Song- Dong & He, Xing-Jin, 2022, Cortiella yatungense, a new species of Cortiella (Apiaceae) from Xizang, China, pp. 189-199 in Phytotaxa 566 (2) on page 195, DOI: 10.11646/phytotaxa.566.2.3, http://zenodo.org/record/711915
Ag-catalyzed C-H/C-C bond functionalization
No full textSilver, known and utilized since ancient times, is a coinage metal, which has been widely used for various organic transformations in the past few decades. Currently, the silver-catalyzed reaction is one of the frontier areas in organic chemistry, and the progress of research in this field is very rapid. Compared with other transition metals, silver has long been believed to have low catalytic efficiency, and most commonly, it is used as either a cocatalyst or a Lewis acid. Interestingly, the discovery of Ag-catalysis has been significantly improved in recent years. Especially, Ag(I) has been demonstrated as an important and versatile catalyst for a variety of organic transformations. However, so far, there has been no systematic review on Ag-catalyzed C-H/C-C bond functionalization. In this review, we will focus on the development of Ag-catalyzed C-H/C-C bond functionalization and the corresponding mechanism.National Basic Research Program of China (973 Program) [2015CB856600]; National Natural Science Foundation of China [21325206, 21562034]; National Young Top-notch Talent Support Program; Ningxia Natural Science Foundation [NZ14037]; Scientific Research Project Foundation of Ningxia Colleges and Universities [NGY2014010]; Research Starting Funds for Imported Talents, Ningxia University [80020242]SCI(E)[email protected]
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