Sequential Alkylation of Tröger's Base. An Approach to New Chiral Ligands

Heterocycles derived from Tröger's base were shown to complex with metal salts in 2:1 ligand:salt ratios as monodentate or bidentate ligands depending on structure.     

Regioselective A-Ring Chlorination of Benzodiazepine Analogues Using tert-Butyl Hypochlorite

Treatment of 2-phenyl-2,3-dihydro-1,4-benzodiazepin-5(4H)-one and a series of 1,4-benzoxazepinone analogues with tert-butyl hypochlorite affords products shown, by NMR and MS spectroscopy, to be chlorinated exclusively in the A-ring at positions 7 and/or 9.     

Synthesis of Tri- and Disalicylaldehydes and Their Chiral Schiff Base Compounds

A suitable procedure for convenient preparation of 1,3,5-tris(4-hydroxy-5-formylphenyl)benzene (6) was exploited via 5-bromosalicylaldehyde as starting reactant. Among the obtained products, compound 6, 4-methoxy-3-formylphenylboronic acid (9), 1,3,5-tris(4-methoxy-5-formylphenyl)benzene (10), and 4-methoxy-4′-hydroxyl-3,3′-diformyl-1,1′-diphenyl (11) had not been reported previously. Two new chiral Schiff base ligands, L1 and L2, were obtained from the tri- or disalicylaldehydes.     

Electrogenerated acetonitrile anions/tetrabutylammonium cations: an effective catalytic system for the synthesis of novel chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidines

An efficient and convenient synthesis of novel chromeno[3′,4′:5,6]pyrano[2,3-d]pyrimidines is described, using the electrogenerated anion of acetonitrile as the base in the presence of tetrabutylammonium fluoride as an effective supporting electrolyte in a one-pot, three-component condensation of barbituric acid, an aromatic aldehyde or isatin, and 4-hydroxycoumarin. The reaction is carried out in an undivided cell containing an iron electrode as the cathode and a Pt electrode as the anode, at a constant current at room temperature.     

Service‐based high‐speed railway base station arrangement

To provide stable and high data rate wireless access for passengers in the train, it is necessary to properly deploy base stations along the railway. We consider this issue from the perspective of service, which is defined as the integral of the time‐varying instantaneous channel capacity. With large‐scale fading assumption, it will be shown that the total service of each base station is inversely proportional to the velocity of the train. Besides, we find that if the ratio of the service provided by a base station in its service region to its total service is given, the base station interval (i.e., the distance between two adjacent base stations) is a constant regardless of the velocity of the train. On the other hand, if a certain amount of service is required, the interval will increase with the velocity of the train. The aforementioned results apply not only to simple curve rails, like line rail and arc rail, but also to any irregular curve rail, provided that the train is traveling at a constant velocity. Furthermore, the new developed results are applied to analyze the on–off transmission strategy of base stations. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,spectral and quantum mechanical studies and molecular docking studies of Schiff base (E)2-hydroxy-5-(((4-(N-pyrimidin-2-yl)sulfamoyl)phenyl)imino)methyl benzoic acid from 5-formyl salicylic acid and sulfadiazine

A new Schiff base (E)2-hydroxy-5-(((4-(N-pyrimidin-2-yl)sulfamoyl)phenyl)imino)methyl benzoic acid (5FSADA) compound was synthesized by condensation of 5-formyl salicylic acid and sulfadiazine, and the product formed was characterized using FTIR and UV–Visible spectroscopy. The geometry was optimized using DFT. The FTIR were computed from DFT and is compared with experimental spectra, followed by detailed vibrational assignment, which shows that the experimental and simulated data is in close agreement. The UV–Vis spectrum calculated using TD-DFT, IEFPCM solvation model with DMSO as solvent. Wave function based properties like localized orbital locator, electron localization function and non-covalent interactions has been studied extensively. The physical properties (ADMET) of the compound 5FSADA indicated that the compound has excellent drug likeness and PASS studies showed that it has anti-infective properties, which is confirmed by a docking score of −9.0 ​kcal/mol.     

Adsorption performance and mechanism of Schiff base functionalized polyamidoamine dendrimer/silica for aqueous Mn(II) and Co(II)

Schiff base functionalized polyamidoamine (PAMAM) dendrimer/silica were prepared for the adsorption of aqueous Mn(II) and Co(II). The effects that influence the adsorption were investigated systematically and the adsorption mechanism was illustrated by theoretical calculation. The optimum adsorption pH are 4 and 6 for Mn(II) and Co(II). Adsorption kinetics follow pseudo-second-order model and the rate-controlling step is film diffusion process. Adsorption isotherm shows that high initial metal ion concentration facilitates the uptake of metal ions. The adsorption capacity increases first and then decreases in the temperature range of 15–35 °C. Density functional theory (DFT) calculation demonstrates that Schiff base functionalized PAMAM dendrimer tends to coordinate Mn(II) and Co(II) with the oxygen atoms of hydroxyl and carbonyl groups, nitrogen of tertiary amine and imino groups. The imino and tertiary amine groups mainly dominate the adsorption. The reproducibility of the adsorbents indicates they can be regenerated by 5% thiourea and 0.5 mol/L HNO₃ solution efficiently.     

Base Metal Catalyzed Isocyanide Insertions

Isocyanides are diverse C₁ building blocks considering their potential to react with nucleophiles, electrophiles, and radicals. Therefore, perhaps not surprisingly, isocyanides are highly valuable as inputs for multicomponent reactions (MCRs) and other one‐pot cascade processes. In the field of organometallic chemistry, isocyanides typically serve as ligands for transition metals. The coordination of isocyanides to metal centers alters the electronic distribution of the isocyano moiety, and reaction pathways can therefore be accessed that are not possible in the absence of the metal. The tunable reactivity of the isocyanide functional group by transition metals has evolved into numerous useful applications. Especially palladium‐catalyzed isocyanide insertion processes have emerged as powerful reactions in the past decade. However, reports on the use of earth‐abundant and cheap base metals in these types of transformations are scarce and have received far less attention. In this Minireview, we focus on these emerging base metal catalyzed reactions and highlight their potential in synthetic organic chemistry. Although mechanistic studies are still scarce, we discuss distinct proposed catalytic cycles and categorize the literature according to 1) the (hetero)atom bound to and 2) the type of bonding with the transition metal in which the (formal) insertion occurs.     

Prediction of Compound Synthesis Accessibility Based on Reaction Knowledge Graph

With the increasing application of deep-learning-based generative models for de novo molecule design, the quantitative estimation of molecular synthetic accessibility (SA) has become a crucial factor for prioritizing the structures generated from generative models. It is also useful for helping in the prioritization of hit/lead compounds and guiding retrosynthesis analysis. In this study, based on the USPTO and Pistachio reaction datasets, a chemical reaction network was constructed for the identification of the shortest reaction paths (SRP) needed to synthesize compounds, and different SRP cut-offs were then used as the threshold to distinguish a organic compound as either an easy-to-synthesize (ES) or hard-to-synthesize (HS) class. Two synthesis accessibility models (DNN-ECFP model and graph-based CMPNN model) were built using deep learning/machine learning algorithms. Compared to other existing synthesis accessibility scoring schemes, such as SYBA, SCScore, and SAScore, our results show that CMPNN (ROC AUC: 0.791) performs better than SYBA (ROC AUC: 0.76), albeit marginally, and outperforms SAScore and SCScore. Our prediction models based on historical reaction knowledge could be a potential tool for estimating molecule SA.     

饮用水中三氯甲烷与其他氯消毒副产物在活性炭上的吸附竞争研究

通过等温吸附实验,探究了三氯甲烷（CHCl₃）与二氯一溴甲烷（CHBrCl₂）、二氯乙酸（Cl₂CHCOOH）在活性炭上的竞争吸附关系,同时探究了在低浓度条件下CHBrCl₂和Cl₂CHCOOH浓度变化对活性炭吸附CHCl₃的影响。实验结果表明,活性炭吸附CHCl₃和CHBrCl₂符合Freundlich模型,对Cl₂CHCOOH的吸附符合Langmuir模型;活性炭对3种消毒副产物均为优先吸附,吸附能力由大到小依次为CHBrCl₂、CHCl₃、Cl₂CHCOOH;低浓度条件下,活性炭对消毒副产物的吸附效果随体系中物质种类的增加而降低;低浓度条件下,Cl₂CHCOOH的浓度变化对CHCl₃的吸附效果影响不大,但吸附效果随水体中CHBrCl₂浓度的升高而降低。