Catalysis by Amberlite IR-120 resin: a rapid and green method for the synthesis of phenols from arylboronic acids under metal, ligand, and base-free conditions

A clean process has been developed for the ipso-hydroxylation of aryl and heteroaryl boronic acids to the corresponding phenols using commercially available and recyclable Amberlite IR-120 resin and aqueous hydrogen peroxide as an oxidizing agent. The ion-exchange sulfonic acid resin catalyst could be readily recycled by filtration and directly reused at least four times without any significant loss of activity.     

A facile synthesis of melatonergic antidepressant agomelatine

Agomelatine was synthesized from 8-aminonaphthalen-2-ol by diazotization-iodination, formylation, C–C bond formation by nitroaldol and Pd/C hydrogenation of β-nitrovinylnaphthalene followed by N-acetylation. The route reported employs readily and commercially viable starting materials and reagents, and can potentially be utilized for process synthesis of agomelatine.     

InCl3 catalyzed three-component synthesis of α-benzylamino coumarins and diketones

A convenient and practical InCl₃ catalyzed three-component reaction of 4-hydroxy coumarin/1,3 diones, aromatic aldehyde, and secondary amine for the synthesis of α-benzylamino coumarins and diketones in good yields has been reported.     

Computational Insight to Improve the Thermal Isomerisation Performance of Overcrowded Alkene‐Based Molecular Motors through Structural Redesign

Synthetic overcrowded alkene‐based molecular motors achieve 360° unidirectional rotary motion of one motor half (rotator) relative to the other (stator) through sequential photochemical and thermal isomerisation steps. In order to facilitate and expand the use of these motors for various applications, it is important to investigate ways to increase the rates and efficiencies of the reactions governing the rotary motion. Here, we use computational methods to explore whether the thermal isomerisation performance of some of the fastest available motors of this type can be further improved by reducing the sizes of the motor halves. Presenting three new redesigned motors that combine an indanylidene rotator with a cyclohexadiene, pyran or thiopyran stator, we first use multiconfigurational quantum chemical methods to verify that the photoisomerisations of these motors sustain unidirectional rotary motion. Then, by performing density functional calculations, we identify both stepwise and concerted mechanisms for the thermal isomerisations of the motors and show that the rate‐determining free‐energy barriers of these processes are up to 25 kJ mol^?1 smaller than those of the original motors. Furthermore, the thermal isomerisations of the redesigned motors proceed in fewer steps. Altogether, the results suggest that the redesigned motors are useful templates for improving the thermal isomerisation performance of existing overcrowded alkene‐based motors.     

Photoswitchable multivalent sugar ligands: synthesis, isomerization, and lectin binding studies of azobenzene-glycopyranoside derivatives

Coating of azobenzene chromophore with multivalent sugar ligands has been accomplished. Such sugar coating allows the study of the isomerization properties of this chromophore in aqueous solutions. The predominantly cis-isomer-containing photostationary state (PS) mixture of these azobenzene derivatives is found to be stable for hours. The rate constants for their isomerization, as well as the Arrhenius activation energies, are determined experimentally. An assessment of the lectin binding properties of the lactoside bearing isomeric azobenzene derivatives, by isothermal calorimetric methods, reveals the existence of an unusual cooperativity in their binding to lectin peanut agglutinin. Thermodynamic parameters evaluated for the trans and the PS mixture are discussed, in detail, for the lactoside bearing bivalent azobenzene derivative.     

Organocatalytic Asymmetric Conjugate Additions to Cyclopent‐1‐enecarbaldehyde: A Critical Assessment of Organocatalytic Approaches towards the Telaprevir Bicyclic Core

In the context of a programme directed at the manufacture of telaprevir, eight possible approaches to its bicyclic α‐amino acid core, based on organocatalytic enantioselective conjugate additions to cyclopent‐1‐enecarbaldehyde, were identified and preliminarily explored. Four reactions, delivering advanced intermediates en route to the target amino acid, were selected for a thorough optimisation. Three of this reactions involved iminium ion catalysis with a prolinol catalyst (addition of nitromethane, nitroacetate and acetamidomalonate) and one was based on a Cinchona‐derived phase‐transfer catalyst (addition of glycine imines). A careful choice of additives allowed lowering of the catalyst loading to 0.5 mol % in some cases. The preparation of intermediates that would give access to the core of telaprevir in good yields and enantioselectivities by exploiting readily available substrates and catalysts, highlights the potential of organocatalytic technology for a cost‐effective preparation of pharmaceuticals.     

Assessment of a composite CC2/DFT procedure for calculating 0–0 excitation energies of organic molecules

The task to assess the performance of quantum chemical methods in describing electronically excited states has in recent years started to shift from calculation of vertical (ΔE_ve) to calculation of 0–0 excitation energies (ΔE₀₀). Here, based on a set of 66 excited states of organic molecules for which high-resolution experimental ΔE₀₀ energies are available and for which the approximate coupled-cluster singles and doubles (CC2) method performs particularly well, we explore the possibility to simplify the calculation of CC2-quality ΔE₀₀ energies using composite procedures that partly replace CC2 with more economical methods. Specifically, we consider procedures that employ CC2 only for the ΔE_ve part and density functional theory methods for the cumbersome excited-state geometry optimisations and frequency calculations required to obtain ΔE₀₀ energies from ΔE_ve ones. The results demonstrate that it is indeed possible to both closely (to within 0.06–0.08 eV) and consistently approximate ‘true’ CC2 ΔE₀₀ energies in this way, especially when CC2 is combined with hybrid density functionals. Overall, the study highlights the unexploited potential of composite procedures, which hitherto have found widespread use mostly in ground-state chemistry, to also play an important role in facilitating accurate studies of excited states.     

Temporal ratiometry to assess dynamic concentration distributions of fluorescent molecules in single live cells during continuous diffusional dosing

The introduction of specific molecules into live cells is a widely used approach to probe cellular mechanisms. Recently, we have reported on the sustained dosing of molecules into single cells via a microscopic diffusion port. Here we describe temporal ratiometry, a method to reconstruct intracellular concentration distribution of the delivered molecules as it varies in time during dosing. To characterize this method, we analyzed fluorescence intensity maps obtained during delivery of Lucifer Yellow CH, LY, a polar fluorophore into A7r5 vascular smooth muscle cells, normal rat kidney epithelial cells (NRKE), and MCF-7 human breast cancer cells. Temporal ratiometry indicates a linear increase in concentration of LY in these cells with a nearly uniform distribution during 20 min of delivery. The method cancels the effects of varying cell height and variable accessible volume on the measured intensities at different locations within the cell. Temporal ratiometry will be useful to estimate dynamic changes in intracellular concentration distributions and thus, facilitate the understanding of transport, binding, sequestration, and efflux of molecules introduced into cells.     

Diffusive logistic equation with constant yield harvesting, I: Steady States

We consider a reaction-diffusion equation which models the constant yield harvesting to a spatially heterogeneous population which satisfies a logistic growth. We prove the existence, uniqueness and stability of the maximal steady state solutions under certain conditions, and we also classify all steady state solutions under more restricted conditions. Exact global bifurcation diagrams are obtained in the latter case. Our method is a combination of comparison arguments and bifurcation theory.