Mechanistic knowledge and noncovalent interactions as the key features for enantioselective catalysed multicomponent reactions: a critical review

2019 ◽  
Vol 17 (31) ◽  
pp. 7260-7269 ◽  
Author(s):  
Luciana M. Ramos ◽  
Marcelo O. Rodrigues ◽  
Brenno A. D. Neto

This critical short review focuses on some key features which determine successful enantioselective catalysed multicomponent reactions (MCRs) and are typically underappreciated in the literature.

Author(s):  
Carmine Lima ◽  
Enzo Martinelli

This paper is intended at highlighting the main mechanical parameters controlling the behavior of the so-called "acceleration-sensitive" Non-Structural Components (NSCs). In the first part a short review of the current state of knowledge and the critical issues related to the prediction of the seismic response of NSCs is reported. Then, the paper presents the results of a numerical parametric analysis intended to capture the key features of the dynamic response of a two-degree-of-freedom (2DOF) system which is supposed to be representative of both the main structure and the "non-structural" component (NSC). Particularly, it allows to simulate the coupled behaviour of both main structure and NSC and evaluating their response. The main parameters controlling the dynamic response of NSCs emerge from this study, which could pave the way towards formulating more mechanically consistent relationships for evaluating the maximum accelerations induced by seismic shakings on NSCs.


Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3419 ◽  
Author(s):  
Antonio Frontera

Noble gas (or aerogen) bond (NgB) can be outlined as the attractive interaction between an electron-rich atom or group of atoms and any element of Group-18 acting as an electron acceptor. The IUPAC already recommended systematic nomenclature for the interactions of groups 17 and 16 (halogen and chalcogen bonds, respectively). Investigations dealing with noncovalent interactions involving main group elements (acting as Lewis acids) have rapidly grown in recent years. They are becoming acting players in essential fields such as crystal engineering, supramolecular chemistry, and catalysis. For obvious reasons, the works devoted to the study of noncovalent Ng-bonding interactions are significantly less abundant than halogen, chalcogen, pnictogen, and tetrel bonding. Nevertheless, in this short review, relevant theoretical and experimental investigations on noncovalent interactions involving Xenon are emphasized. Several theoretical works have described the physical nature of NgB and their interplay with other noncovalent interactions, which are discussed herein. Moreover, exploring the Cambridge Structural Database (CSD) and Inorganic Crystal Structure Database (ICSD), it is demonstrated that NgB interactions are crucial in governing the X-ray packing of xenon derivatives. Concretely, special attention is given to xenon fluorides and xenon oxides, since they exhibit a strong tendency to establish NgBs.


Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 132
Author(s):  
Brenno A. D. Neto ◽  
Rafael O. Rocha ◽  
Marcelo O. Rodrigues

In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented.


2021 ◽  
Vol 9 ◽  
Author(s):  
Livio Conti ◽  
Piergiorgio Picozza ◽  
Alessandro Sotgiu

We aim at giving a short review of the seismo-associated phenomena detected on ground that in recent years have been investigated as possible earthquake precursors. The paper comes together with a companion article–published on this same volume by Picozza et al., 2021–devoted to summarize the space-based observation of earthquake–precursors by satellites missions. In the present work, we give an overview of the observations carried out on ground in order to identify earthquake precursors by distinguishing them from the large background constituted by both natural non-seismic and artificial sources. We start discussing the measurements of mechanical parameters and variations of geochemical fluids detected before earthquakes; then we review thermal and atmospheric oscillations; finally, observations of electromagnetic and ionospheric parameters possibly related to the occurrence of impeding earthquakes are discussed. In order to introduce a so large field of research, we focus only on some main case studies and statistical analyses together with the main hypotheses and models proposed in literature in order to explain the observed phenomenology.


2021 ◽  
Author(s):  
Marcelo O. Rodrigues ◽  
Marcos N. Eberlin ◽  
Brenno A. D. Neto

Buildings ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 7 ◽  
Author(s):  
Carmine Lima ◽  
Enzo Martinelli

This paper aims at highlighting the main mechanical parameters controlling the behavior of the so-called ‘acceleration-sensitive’ non-structural components (NSCs). The first reports a short review of the current state of knowledge and the critical issues dealing with the prediction of the seismic response of NSCs. Then, the paper presents the results of a numerical parametric analysis intended to capture the key features of the coupled dynamic response of a two-degree-of-freedom (2DOF) system supposed to be representative of both main structure and ‘non-structural’ component (NSC). The main parameters controlling the dynamic response of NSCs emerge from this study, which could pave the way towards formulating more mechanically consistent relationships for evaluating the peak accelerations induced by seismic shakings on NSCs in buildings.


Synthesis ◽  
2017 ◽  
Vol 28 (19) ◽  
pp. 4414-4433 ◽  
Author(s):  
Xuefeng Jiang ◽  
Minghao Feng

Arynes are important building blocks for introducing aromatic rings into molecules and they are frequently utilized in syntheses. Historically, arynes were generated under harsh conditions and this limited their use. Arynes can now be generated under milder conditions, e.g. from 2-(trimethylsilyl)phenyl triflate, and utilized in transition-metal­ catalyzed reactions such as [2+2+2] reactions, insertion into σ-bonds, cascade cyclizations and C–H activation reactions. This short review focuses on transition-metal-catalyzed reactions relevant to aryne intermediates generated from 2-(trimethylsilyl)phenyl triflates and other aryne precursors.1 Introduction2 [2+2+2] Reactions3 Aryne Insertion into a σ-Bond4 Cascade Cyclizations5 C–H Activation6 Multicomponent Reactions (MCRs)7 Conclusion


Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3224-3236 ◽  
Author(s):  
Martin Breugst ◽  
Daniel von der Heiden ◽  
Julie Schmauck

Noncovalent interactions play an important role in many biological and chemical processes. Among these, hydrogen bonding is very well studied and is already routinely used in organocatalysis. This Short Review focuses on three other types of promising noncovalent interactions. Halogen bonding, chalcogen bonding, and anion-π bonding have been introduced into organocatalysis in the last few years and could become important alternate modes of activation to hydrogen bonding in the future.1 Introduction2 Halogen Bonding3 Chalcogen Bonding4 Anion-π Bonding5 Conclusions


Author(s):  
R. E. Ferrell ◽  
G. G. Paulson ◽  
C. W. Walker

Selected area electron diffraction (SAD) has been used successfully to determine crystal structures, identify traces of minerals in rocks, and characterize the phases formed during thermal treatment of micron-sized particles. There is an increased interest in the method because it has the potential capability of identifying micron-sized pollutants in air and water samples. This paper is a short review of the theory behind SAD and a discussion of the sample preparation employed for the analysis of multiple component environmental samples.


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