Sichuan University

About: Sichuan University is a education organization based out in Chengdu, China. It is known for research contribution in the topics: Population & Catalysis. The organization has 107623 authors who have published 102844 publications receiving 1612131 citations. The organization is also known as: Sìchuān Dàxué.

The Spatially Oriented Charge Flow and Photocatalysis Mechanism on Internal van der Waals Heterostructures Enhanced g-C3N4

Abstract: Undirected charge transfer and inhibited interlayer electron migration largely limit the photocatalytic efficiency of two-dimensional (2D) layered graphitic carbon nitride (g-C3N4). Herein, we present a facile chemical approach to forming internal van der Waals heterostructures (IVDWHs) within g-C3N4, which enhance the interlayer coulomb interaction and facilitate the spatially oriented charge separation. Such a structure, generated through simultaneous g-C3N4 intralayer modification by O and interlayer intercalation by K, enables the oriented charge flow between the layers, enhancing the accumulation of the localized electrons and promoting the production of active radicals for the activation of reactants as suggested by density functional theory calculations. The resultant O, K-functionalized g-C3N4 with IVDWHs shows an enhanced photocatalytic activity, with nearly 100% enhancement of NO purification efficiency compared with pristine g-C3N4. The reaction mechanism for NO purification is also provided, i...

Hesitant Fuzzy Linguistic Term Set and Its Application in Decision Making: A State-of-the-Art Survey

Abstract: The hesitant fuzzy linguistic term set (HFLTS) has gained great success as it can be used to represent several linguistic terms or comparative linguistic expressions together with some context-free grammars. This new approach has enabled the analysis and computing of linguistic expressions with uncertainties and opened the door for the possibility to develop more comprehensive and powerful decision theories and methods based on linguistic knowledge. Lots of new approaches and proposals for decision-making problems have been proposed to overcome the limitations of previous linguistic decision-making approaches. Now and in the future, decision-making methodologies and algorithms with hesitant fuzzy linguistic models would be a quite promising research line representing a high-quality breakthrough in this topic. To facilitate the study on HFLTS theory, this paper makes a state-of-the-art survey on HFLTSs based on the 134 selected papers from Web of Sciences published from January 2012 to October 2017. We justify the motivation, definitions, operations, comparison methods and measures of HFLTSs. We also summarize the different extensions of HFLTSs. The studies on multiple criteria decision making (MCDM) with HFLTSs in terms of aggregation operators and MCDM methods are clearly reviewed. We also conduce some overviews on decision making with hesitant fuzzy linguistic preference relations. The applications, research challenges and future directions are also given.

Chemoselective Asymmetric N‐Allylic Alkylation of Indoles with Morita–Baylis–Hillman Carbonates

Abstract: The indole framework represents a key structural motif in a large number of biologically active natural products and pharmaceutical compounds. Consequently, modifications on the indole structure, including the development of enantioselective variants, have triggered increasing interests. Because of the inherent nucleophilic characteristics of indole compounds, their reactions preferentially take place at the C3-position of the ring system. As a result, the majority of enantioselective reactions of indoles focus on the C3-selective addition of electron-rich indoles to electrophilic imines, epoxides, carbonyl compounds, a,b-unsaturated carbonyl compounds, and nitroalkenes etc., thus leading to the formation of diversely structured enantioenriched C3-functionalized indole derivatives. Recently, the enantioselective synthesis of C2-substituted indoles has also been realized through the asymmetric alkylation of 4,7-dihydroindoles and subsequent oxidation. In sharp contrast to the progress in enantioselective alkylation at the C3or C2-positions, the asymmetric Nalkylation of indoles has been underdeveloped: probably because of the privileged C3-chemoselectivity of indole compounds. The limited examples include the palladiumcatalyzed N-allylic alkylation of 3-substituted indoles developed by Trost et al. and the enantioselective intramolecular aza-Michael addition of tethered indole-2-carboxylates under chiral phase-transfer catalysis developed by Bandini et al. Indeed, N-alkylated indoles have been applied as useful intermediates for the synthesis of polyheterocycles and occur widely among natural products and biologically active pharmaceuticals (Scheme 1). For example, mitomycin C exhibits potent antitumour activity and is used clinically in the treatment of certain cancers. Yuremamine, which was recently isolated from the stem bark of Mimosa hostilis, shows hallucinogenic and psychoactive effects. Pyrrolo[3,2,1-ij]quinoline derivatives are active antihistamines and inhibitors of leukotriene, and they offer the possibility of a novel multimediator approach to the treatment of allergic diseases. Therefore, it would be extremely desirable to develop effective protocols to access optically pure N-alkylated indoles. Recently, the allylic alkylation of Morita-Baylis–Hillman (MBH) adducts catalyzed by a metal-free organic Lewis base has emerged as an attractive strategy to prepare multifunctional compounds. Our research group has also reported that modified cinchona alkaloids are outstanding catalysts for the asymmetric allylic alkylation of a,a-dicyanoolefins with MBH carbonates. We anticipated that, as outlined in Scheme 2, the deprotonation of the acidic NH group of the