Exploring the Chemistry of the Mechanical Bond: Synthesis of a [2]Rotaxane through Multicomponent Reactions

© 2023 The Authors. Published by American Chemical Society and Division of Chemical Education, Inc. This manuscript version is made available under the CC-BY 4.0 license https://creativecommons.org/licenses/by/4.0/ This document is the Published Manuscript version of a Published Work that appeared in final form in Journal of Chemical Education. To access the final edited and published work see https://doi.org/10.1021/acs.jchemed.3c00163The synthesis of a [2]rotaxane through three- or five-component coupling reactions has been adapted to an organic chemistry experiment for upper-division students. The experimental procedure addresses the search for the most favorable reaction conditions for the synthesis of the interlocked compound, which is obtained in a yield of up to 71%. Moreover, the interlocked nature of the rotaxane is proven by NMR spectroscopy. The content of the sessions has been designed on the basis of a proactive methodology whereby upper-division undergraduate students have a dynamic role. The laboratory experience not only introduces students to the chemistry of the mechanical bond but also reinforces their previous knowledge of basic organic laboratory procedures and their skills with structural elucidation techniques such as NMR and FT-IR spectroscopies. The experiment has been designed in such a customizable way that both experimental procedures and laboratory material can be adapted to a wide range of undergraduate course curricula

Mechanically interlocked molecules in metal–organic frameworks

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemical Society Reviews, copyright © Royal Society of Chemistry after peer review and technical editing by the publisher. To access the final edited and published work see: https://pubs.rsc.org/en/content/articlelanding/2022/CS/D2CS00167EMechanically interlocked molecules (MIMs) have great potential in the development of molecular machinery due to their intercomponent dynamics. The incorporation of these molecules in a condensed phase makes it possible to take advantage of the control of the motion of the components at the macroscopic level. Metal–organic frameworks (MOFs) are postulated as ideal supports for intertwined molecules. This review covers the chemistry of the mechanical bond incorporated into metal–organic frameworks from the seminal studies to the latest published advances. We first describe some fundamental concepts of MIMs and MOFs. Next, we summarize the advances in the incorporation of rotaxanes and catenanes inside MOF matrices. Finally, we conclude by showing the study of the rotaxane dynamics in MOFs and the operation of some stimuli-responsive MIMs within MOFs. In addition to emphasising some selected examples, we offer a critical opinion on the state of the art of this research field, remarking the key points on which the future of these systems should be focused

Estudio de la reactividad de viniliminofosforanos frente a compuestos carbonílicos (alfa-beta)-insaturados : síntesis de 2-,3 y 4-arilpiridinas / Aurelia Pastor Vivero ; director Pedro Molina Buendía.

Tesis-Universidad de Murcia.Consulte la tesis en: BCA. GENERAL. ARCHIVO UNIVERSITARIO. T.M.-1444.CRAI CIENCIAS. DEPOSITO. T.D. 293

5-Alkenylthiazoles as In-Out Dienes in Polar [4+2] Cycloaddition Reactions

5-Alkenyl-2-aminothiazoles react as in-out dienes with a wide range of electron-poor dienophiles leading to the corresponding cycloaddition products in good to excellent yields. The [4+2] cycloadditions of 5-alkenyl-2-aminothiazoles can be classified as site-selective since only the diene moiety including the formal C-C double bond of the heterocycle and that of the side-chain is involved. Calculations of the HOMO energy values of representative 5-alkenyl-2-aminothiazoles are disclosed The cycloadditions are endo-selective with N-phenylmaleimide or maleic anhydride and regioselective when the reactions are conducted with non symmetrical dienophiles. Completely oxidized cycloadducts are obtained in the reactions of 5-alkenyl-2-aminothiazoles with naphthoquinone or DMAD. Unexpectedly, the reactions with PTAD are not stereospecific. A mechanism placed at the concerted/stepwise boundary is proposed

Maximizing the [c2]daisy chain to lasso ratio through competitive self-templating clipping reactions

©2021. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in [Chemical Communications]. To access the final edited and published work see[https://doi.org/10.1039/D1CC05942D]Self-templating two-component coupling reactions allowed the isolation of two threaded products with different molecular sizes: a lasso-type [1]rotaxane and a [c2]daisy chain rotaxane. Their distribution in the final reaction mixture varies as a factor of the concentration of the reactants. Through this methodology we obtained a large 84-membered cyclic multistation [2]rotaxane

4-Alkenyl-2-aminothiazoles: Smart Dienes for Polar [4 + 2] Cycloadditions

An exhaustive investigation on the [4+2] cycloadditions of 4-alkenyl-2-aminothiazoles with a wide range of dienophiles has been carried out. 4-Alkenyl-2-aminothiazoles act as good in-out dienes reacting with dienophiles bearing electron-withdrawing groups. The heteroannulations, typically conducted under mild conditions, are endo-selective when cyclic dienophiles are employed and regioselective when the reactions are conducted with non symmetric dienophiles. The endo-selective processes presumably take place by concerted but highly asynchronous mechanisms. By contrast, the low levels of endo selectivity and the lack of stereospecificity in the reactions with certain acyclic dienophiles point to a stepwise mechanism with a zwitterion as the most plausible intermediate. The course of the reaction changes when the highly reactive PTAD and TCNE are used as dienophiles since only addition products are obtained. Calculations of the HOMO and LUMO energy values of representative 4-alkenyl-2-aminothiazoles and the results of π-facial diastereoselective processes by using chiral substrates are also disclosed

Light-driven exchange between extended and contracted lasso-like isomers of a bistable [1]rotaxane

The synthesis of a set of benzylic amide [1]rotaxanes via a self-templating clipping approach is described. This methodology supposes the 1+1 coupling of isophthaloyl dichloride with an acyclic diamine precursor incorporating a templating arm. The structure of the threaded compounds was determined in both solution and solid state. The conversion into the corresponding unthreaded isomers, also obtained by deslipping of [2]rotaxane models, was evaluated in competitive and non-competitive hydrogen-bonding solvents. The switch of the extended and contracted lasso-like isomers of a bistable [1]rotaxane by an olefin isomerization promoted by UV light irradiation was also accomplished and their ring positional integrity examined

Exploring the Conversion of Macrocyclic 2,2 '-Biaryl Bis(thioureas) into Cyclic Monothioureas: An Experimental and Computational Investigation

Macrocyclic bis(thioureas) derived from 2,2’-biphenyl and binaphthyl skeletons have been synthesized by reaction of 2,2’-diaminobiaryl and 2,2’-bis(isothiocyanato)biaryl derivatives. The splitting of these bis(thioureas) into two units of the respective cyclic monothioureas has been monitored by NMR, shedding some light on the factors that control these processes. Additionally, a computational study revealed up to three mechanistic paths for the conversion of the 2,2’-biphenyl-derived bis(thiourea) into the corresponding monothiourea. The proposed mechanisms account for the participation of a molecule of water as an efficient proton-switch, as well as for different classes of putative intermediates. The computational study also supports the ability of the thiourea group to participate in a plethora of processes, such as prototropic equilibria, sigmatropic shifts, heteroene and retro-heteroene reactions, and cis-trans isomerizations

Co-conformational Exchange Triggered by Molecular Recognition in a Di(acylamino)pyridine-Based Molecular Shuttle Containing Two Pyridine Rings at the Macrocycle

We describe the incorporation of endo-pyridine units into the tetralactam ring of di(acylamino)pyridine-based rotaxanes. This macrocycle strongly associates with the linear interlocked component as confirmed by X-ray diffraction studies of rotaxane 2b. Dynamic NMR studies of 2b in solution revealed a rotational energy barrier that was higher than that of the related rotaxane 2a, which lacks of pyridine rings in the macrocycle. The macrocycle distribution of the molecular shuttle 4b, containing two endo-pyridine rings, shows that the major co-conformer is that with the cyclic component sitting over the di(acylamino)pyridine station. DFT calculations also support the marked preference of the ring for occupying the heterocyclic binding site. The association of N-hexylthymine with the di(acylamino) pyridine binding site of 4b led to the formation of a rare 'S'-shaped co-conformer in which the tetralactam ring interacts simultaneously with both stations of the thread

Versatile control of the submolecular motion of di(acylamino)pyridine-based [2]rotaxanes

http://dx.doi.org/10.1039/C5SC00790AA cyclic network of chemical reactions has been conceived for exchanging the dynamic behaviour of di(acylamino)pyridine-based rotaxanes and surrogates. X-ray diffraction studies revealed the intercomponent interactions in these interlocked compounds and were consistent with those found in solution by dynamic NMR experiments. This particular binding site was incorporated into a molecular shuttle enabled for accessing two states with an outstanding positional discrimination through chemical manipulation. Furthermore, the ability of the di(acylamino)pyridine domain to associate with external binders with a complementary array of HB donor and acceptor sites was exploited for the advance of an unprecedented electrochemical switch operating through a reversible anion radical recognition process.This work was supported by the MICINN (Projects CTQ2008-05827/BQU and CTQ2009-12216/BQU), and Fundacion Seneca-CARM (Project 08661/PI/08). A.M.-C. thanks the Marie Curie COFUND and U-IMPACT programs for a postdoctoral contract (Grant Agreement 267143). M.D.S. thanks the University of Glasgow for a Kelvin-Smith Research Fellowship and the EPSRC for a Small Equipment grant