One-pot two-step synthesis of 4-vinylphenols from 4-hydroxy substituted benzaldehydes under microwave irradiation: a new perspective on the classical Knoevenagel-Doebner reaction

The classical Knoevenagel-Doebner reaction is reinvestigated wherein the direct synthesis of substituted 4-vinylphenols instead of the expected 4-hydroxycinnamic acids is described. The condensation reaction is performed on 4-hydroxy substituted benzaldehydes and malonic acid with a mixture of acetic acid-piperidine as condensing agent under focused microwave irradiation. The occurrence of simultaneous condensation-double decarboxylation without the use of any decarboxylating agent is a new finding, the reaction being facilitated solely by the hydroxy substituent and microwave irradiation effect.     

Promoting electrochemical conversion of CO2 to formate with rich oxygen vacancies in nanoporous tin oxides

In CO₂ electrochemical reduction, nanoporous SnO_x-300 with high-level oxygen vacancies exhibited a partial current density of 15 mA/cm² with the Faradaic efficiency (FE) of 88.6% for HCOOH production at 0.98 V versus RHE.     

Assembly of New Heterocycles through an Effective Use of Bisaldehydes by Using a Sequential GBB/Ugi Reaction

A facile route for the assembly of new bis‐heterocyclic imidazo[2,1‐b][1,3]thiazinyl/benzothiazoyl‐phenyl)benzamide scaffolds through a two‐step Groebke–Blackburn–Bienaymé (GBB)/Ugi reaction sequence is reported, which establishes multiple points of diversity in the final products. The highlights of this procedure are the survival of the aldehyde group following the GBB reaction without the need for additional protection/deprotection steps. Moreover, the reaction is operationally simple, with the absence of any catalyst, and exhibits excellent functional‐group tolerance under minutes of microwave irradiation.     

A New Conformationally Symmetrical Calix[4]pyrrole Based Supramolecular System for Liquid Crystalline and Window Layer Solar Cell Applications

The newly symmetrical liquid crystalline compounds (CPB₁ – CPB₄) based on calix[4]pyrrole as central rigid core are synthesized via esterification reaction. All the four functionalized compounds exhibit columnar hexagonal phase (Col_h) over a higher mesophase temperature range and further stabilized mesophase upto room temperature. The thermal behavior and optical texture are identified by using differential scanning calorimetry (DSC), Polarizing optical microscopy (POM) while the molecular organization of compound in mesogenic state by X-ray diffraction technique. The molecular system based on calix[4]pyrrole core with symmetrical nature exhibited columnar type self-assembly at room temperature. All these four supramolecules with different side spacer show higher thermal stability. Based upon the optimization, compound CPB₂ has been further tested to implicate as optical window layer in thin films solar cell devices. The calix[4]pyrrole functionalized supramolecular liquid crystalline compound based thin films showed suitable transmittance, optical energy band gap together with absorbance and extinction coefficient. The linear dependence of current on the voltage demonstrated Ohmic behavior of the CPB₂ films. The surface morphology to the developed samples designated nearly uniform deposition of the CPB₂ thin films together with grain growth. The findings warrant suitability of the films to implicate these as an eco-friendly optical window layer in thin films based solar cells.     

Synthesis of 5-(phenylsulfanyl)-1,4-dihydropyrazine-2,3-diones via an unexpected microwave-assisted cascade reaction

An unprecedented route for the synthesis of N-1 substituted 5-(phenylsulfanyl)-1,4-dihydropyrazine-2,3-diones is disclosed starting from 5-chloro-3-(phenylsulfanyl)pyrazin-2(1H)-ones. The method comprises treatment of various 5-chloro-3-(phenylsulfanyl)pyrazin-2(1H)-ones with Na₂CO₃ in water under microwave irradiation providing the respective 5-(phenylsulfanyl)-1,4-dihydropyrazine-2,3-diones in good yields, via hydrolysis of the thioether bond and subsequent nucleophilic displacement of the chlorine by the in situ generated thiophenol. The obtained compounds are excellent precursors for the diversity oriented synthesis of pharmacologically active α,β-dicarbonyl compounds.     

Molecular modeling of surfactant covered oil-water interfaces: Dynamics, microstructure, and barrier for mass transport

Mass transport across surfactant-covered oil-water interfaces of microemulsions plays an important role in numerous applications. In the current work, we use coarse-grained molecular dynamics simulations to investigate model systems containing flat hexadecane-water interfaces covered by monolayers of nonionic surfactants of various lengths. Several properties of the surfactant monolayers relevant to the mass transport are considered, including the monolayer microstructure, dynamics, and a free energy barrier to the solute transport. It is observed that the dominant contribution of a surfactant monolayer to the free energy barrier is a steric repulsion caused by a local density increase inside the monolayer. The local densities, and hence the free energy barriers, are larger for monolayers composed of longer surfactants. Since it is likely that the solute transport mechanism involves a sequence of jumps between short-lived pores within a monolayer, we perform a detailed analysis of structure, size, and lifetime of these pores. We demonstrate that the pore statistics is consistent with predictions of percolation theory and apply this theory to identify the characteristic length scale of the monolayer microstructure. The obtained pore structures are sensitive to minute changes of surfactant configurations occurring on the picosecond time scale. To reduce this sensitivity, the pores are averaged over short time intervals. The optimal duration of these time intervals is estimated from analysis of dynamics of pores with diameters comparable to or exceeding the characteristic percolation length scale. The developed approach allows one to filter out transient events of the pore dynamics and to focus on events leading to substantial changes of the monolayer microstructure.     

An alternate approach to solve two-level hierarchical time minimization transportation problem

This paper discusses a two-level hierarchical time minimization transportation problem, which is an important class of transportation problems arising in industries. This problem has been studied by various researchers (Sharma et al. in Eur J Oper Res 246:700–707, 2015; Sonia and Puri in TOP 12(2):301–330, 2004; Xie et al. in Comput Oper Res 86:124–139, 2017) and therefore, a number of polynomial time iterative algorithms are available to find its solution. All the existing algorithms, though efficient, have some shortcomings. The current study proposes an alternate solution algorithm for the problem that is more efficient in terms of computational time than the existing algorithms. The results justifying the underlying theory of the proposed algorithm are given. Further, a detailed comparison of the computational behaviour of all the algorithms for randomly generated instances of this problem, of different sizes validates the efficiency of the proposed algorithm.

     

Copper Catalyzed ATRP of Methyl Methacrylate Using Aliphatic α-Bromo Ketone Initiator

The atom transfer radical polymerization (ATRP) of MMA was examined using 3-bromo-3-methyl-butanone-2 (MBB) as an initiator in the presence of CuBr as catalyst and 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (BPIEP) as a tridentate N-donor ligand. The effect of various other N-donor ligands including a bisoxazoline ligand, namely, 2,6-bis(4,4-dimethyl-2-oxazolin-2-yl) pyridine (dmPYBOX) was studied in ATRP and reverse ATRP of MMA. The ATRP of MMA in toluene at 90 °C using MBB as initiator was relatively slow in the case of bidentate and faster in the case of tridentate N-donor ligands. The apparent rate constant, k_app, with MBB as initiator and BPIEP as ligand in toluene (50%, v/v) at 90 °C was found to be 7.15 × 10⁻⁵ s⁻¹. In addition, reverse ATRP of MMA in diphenylether at 70 °C using BPIEP/CuBr₂ as catalyst system was very effective in reducing the reaction time from several hours to 24 h for polymerization of MMA.     

Theoretical study of photoinduced superconductors in a two band model

A study of photoinduced high-T_c superconductivity is presented by canonical two-band BCS model containing Fermi surfaces of p and d holes. We have obtained two superconducting gaps from this model. Studies of chemical potential and hole concentration dependences on critical temperature (T_c) are made. The enhancement of T_c is found due to doping.The study of specific heat and density of states based on this model is also presented. The dependence T_c(n_h) for the system YBa₂Cu₃O_7?x (1 2 3) obtained theoretically agrees with the available experimental data.     

A convenient synthetic route for alkynylselenides from alkynyl bromides and diaryl diselenides employing copper(I)/imidazole as novel catalyst system

A mild, convenient, and effective strategy is developed for the synthesis of alkynyl selenides from alkynyl bromides and respective diselenides using CuI/imidazole as a novel catalyst system with Mg as additive. The procedure affords the title compounds in moderate to good yield (51-89%). The main advantages of the protocol include the use of inexpensive copper catalyst, a novel Cu(I)/imidazole combination, and good yield of the products.