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91.
Amit Mondal Biswajit Bhattacharya Susobhan Das Surojit Bhunia Rituparno Chowdhury Somnath Dey C. Malla Reddy 《Angewandte Chemie (International ed. in English)》2020,59(27):10971-10980
Ductility is a common phenomenon in many metals but is difficult to achieve in molecular crystals. Organic crystals bend plastically on one or two face‐specific directions but fracture when stressed in any other arbitrary directions. An exceptional metal‐like ductility and malleability in the isomorphous crystals of two globular molecules, BH3NMe3 and BF3NMe3, is reported, with characteristic tensile stretching, compression, twisting, and thinning. The mechanically deformed samples, which transition to lower symmetry phases, retain good long‐range order amenable to structure determination by single‐crystal X‐ray diffraction. Molecules in these high‐symmetry crystals interact through electrostatic forces (B??N+) to form columnar structures with multiple slip planes and weak dispersive forces between columns. On the other hand, the limited number of facile slip planes and strong dihydrogen bonding in BH3NHMe2 negates ductility. Our study has implications for the design of soft ferroelectrics, solid electrolytes, barocalorics, and soft robotics. 相似文献
92.
Amit Kumar Nitee Kumari Sateesh Dubbu Sumit Kumar Taewan Kwon Jung Hun Koo Jongwon Lim Inki Kim Yoon‐Kyoung Cho Junsuk Rho In Su Lee 《Angewandte Chemie (International ed. in English)》2020,59(24):9460-9469
Interest and challenges remain in designing and synthesizing catalysts with nature‐like complexity at few‐nm scale to harness unprecedented functionalities by using sustainable solar light. We introduce “nanocatalosomes”—a bio‐inspired bilayer‐vesicular design of nanoreactor with metallic bilayer shell‐in‐shell structure, having numerous controllable confined cavities within few‐nm interlayer space, customizable with different noble metals. The intershell‐confined plasmonically coupled hot‐nanospaces within the few‐nm cavities play a pivotal role in harnessing catalytic effects for various organic transformations, as demonstrated by “acceptorless dehydrogenation”, “Suzuki–Miyaura cross‐coupling” and “alkynyl annulation” affording clean conversions and turnover frequencies (TOFs) at least one order of magnitude higher than state‐of‐the‐art Au‐nanorod‐based plasmonic catalysts. This work paves the way towards next‐generation nanoreactors for chemical transformations with solar energy. 相似文献
93.
1,3‐Difunctionalizations of [1.1.1]Propellane via 1,2‐Metallate Rearrangements of Boronate Complexes
Songjie Yu Changcheng Jing Adam Noble Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2020,59(10):3917-3921
1,3‐Disubstituted bicyclo[1.1.1]pentanes (BCPs) are valuable bioisosteres of para‐substituted aromatic rings. The most direct route to these structures is via multicomponent ring‐opening reactions of [1.1.1]propellane. However, challenges associated with these transformations mean that difunctionalized BCPs are more commonly prepared by multistep reaction sequences with BCP‐halide intermediates. Herein, we report three‐ and four‐component 1,3‐difunctionalizations of [1.1.1]propellane with organometallic reagents, organoboronic esters, and a variety of electrophiles. This process is achieved by trapping intermediate BCP‐metal species with boronic esters to form boronate complexes, which are versatile intermediates whose electrophile‐induced 1,2‐metallate rearrangement chemistry enables a broad range of C?C bond‐forming reactions. 相似文献
94.
Hui Wang Changcheng Jing Adam Noble Varinder Kumar Aggarwal 《Angewandte Chemie (International ed. in English)》2020,59(39):16859-16872
The stereospecific 1,2‐migration of boronate complexes is one of the most representative reactions in boron chemistry. This process has been used extensively to develop powerful methods for asymmetric synthesis, with applications spanning from pharmaceuticals to natural products. Typically, 1,2‐migration of boronate complexes is driven by displacement of an α‐leaving group, oxidation of an α‐boryl radical, or electrophilic activation of an alkenyl boronate complex. The aim of this article is to summarize the recent advances in the rapidly expanding field of electrophile‐induced stereospecific 1,2‐migration of groups from boron to sp2 and sp3 carbon centers. It will be shown that three different conceptual approaches can be utilized to enable the 1,2‐migration of boronate complexes: stereospecific Zweifel‐type reactions, catalytic conjunctive coupling reactions, and transition metal‐free sp2–sp3 couplings. A discussion of the reaction scope, mechanistic insights, and synthetic applications of the work described is also presented. 相似文献
95.
Debaki Ghosh Souradeep Basu Monisha Singha Joyee Das Prabuddha Bhattacharya Amit Basak 《Tetrahedron letters》2017,58(21):2014-2018
Three crescent shaped heterocycle-fused phenanthrene based systems 1–3 have been synthesized starting from benzene (or substituted benzene) 1,2-bis-propargyl alcohols. Bis-alkylation with propargylic bromides provided the key intermediate, the bis-propargyl bis-ethers. In spite of the possibility of many competing reactions, the latter underwent facile double Garratt-Braverman cyclization to provide compounds 1–3 in near quantitative yield, in a striking reaction involving the formation of four C–C bonds in a single step. Compounds 1–3 showed binding interaction with DNA, predominantly, via groove binding along with partial intercalation (combilexins). Molecular docking study supported the proposed binding modes. 相似文献
96.
Amit Bermanis Amir Averbuch Ronald R. Coifman 《Applied and Computational Harmonic Analysis》2013,34(1):15-29
We introduce a multiscale scheme for sampling scattered data and extending functions defined on the sampled data points, which overcomes some limitations of the Nyström interpolation method. The multiscale extension (MSE) method is based on mutual distances between data points. It uses a coarse-to-fine hierarchy of the multiscale decomposition of a Gaussian kernel. It generates a sequence of subsamples, which we refer to as adaptive grids, and a sequence of approximations to a given empirical function on the data, as well as their extensions to any newly-arrived data point. The subsampling is done by a special decomposition of the associated Gaussian kernel matrix in each scale in the hierarchical procedure. 相似文献
97.
98.
Yogendra K. Gautam Amit K. ChawlaRajan Walia R.D. AgrawalRamesh Chandra 《Applied Surface Science》2011,257(14):6291-6295
Structural and optical properties of pure Mg thin film coated with Pd have been investigated. Pd-capped Mg thin films had been prepared by DC magnetron sputtering. This work presents an ex situ study on hydrogenation and dehydrogenation kinetics of Pd/Mg films at different conditions using XRD, AFM and optical spectrophotometer. We have succeeded to load thin films of Mg to MgH2 at normal temperature and normal pressure of hydrogen gas. In hydrogenation, α-MgH2 phase of magnesium hydride was observed in hydrogenated films at 200 °C and γ-MgH2 at 250 °C respectively. The desorption kinetics in vacuum also revealed the phase transformation α-MgH2 to γ-MgH2. A reflectance change was observed in hydrogenated films in comparison of as deposited thin film. Hydrogenated (H loaded) samples were observed partially transparent in comparison of as deposited. 相似文献
99.
Muhammad Arshad M. Alejandro Fernández Eoghan M. McGarrigle Varinder K. Aggarwal 《Tetrahedron: Asymmetry》2010,21(13-14):1771-1776
The epoxidation of meroquinene aldehyde with a chiral sulfur ylide as the key step in the synthesis of quinine and quinidine is described. The epoxidation reactions proceed under reagent control with high selectivity and good yield. The effect of sulfide and ylide substituents on the stereochemical outcome of the reaction is discussed. 相似文献
100.