Formation of a vanillic Mannich base — theoretical study

One-pot anti-Mannich reaction of vanillin, aniline and cyclohexanone was successfully catalyzed by ionic liquid triethanolammonium chloroacetate, at room temperature. Yield of the obtained Mannich base was very good and excellent diastereoselectivity was achieved. Mechanism of the reaction was investigated using the density functional theory. The reaction started with a nucleophilic attack of aniline nitrogen at the carbonyl group of vanillin. The intermediate α-amino alcohol formed in this way was further subjected to protonation by the triethanolammonium ion yielding the imminium ion. Theoretically, the obtained imminium ion and the enol form of cyclohexanone can build the protonated Mannich base via the anti and syn pathways. The chloroacetic anion spontaneously abstracts the proton yielding the final product of the reaction anti 2-[1-(N-phenylamino)-1-(4-hydroxy-3-methoxyphenyl)]methylcyclohexanone (MB-H). The syn pathway requires lower activation energy but the anti pathway yields a thermodynamically more stable product, which implies that the examined Mannich reaction is thermodynamically controlled.     

Using controlled radical polymerization to confirm the lower critical solution temperature of an N‐(alkoxyalkyl) acrylamide polymer in aqueous solution

N‐(3‐Methoxypropyl) acrylamide (MPAM) was polymerized by controlled radical polymerization (CRP) methods such as nitroxide‐mediated polymerization (NMP) and reversible addition–fragmentation chain‐transfer polymerization (RAFT). CRP was expected to yield well‐defined polymers with sharp lower critical solution temperature (LCST) transitions. NMP with the BlocBuilder (2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropanoic acid) and SG1 ([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] oxidanyl) initiating system revealed low yields and lack of control (high dispersity, ? ～ 1.5–1.6, and inhibition of chain growth). However, RAFT was far more effective, with linear number average molecular weight, , versus conversion, X, plots, low ? ～ 1.2–1.4 and the ability to form block copolymers using N,N‐diethylacrylamide (DEAAM) as the second monomer. Poly(MPAM) (with = 13.7–25.3 kg mol^?1) thermoresponsive behavior in aqueous media revealed cloud point temperatures (CPT)s between 73 and 92 °C depending on solution concentration (ranging from 1 to 3 wt %). The and the molecular weight distribution were the key factors determining the CPT and the sharpness of the response, respectively. Poly(MPAM)‐b‐poly(DEAAM) block copolymer ( = 22.3 kg mol^?1, ? = 1.41, molar composition F_DEAAM = 0.38) revealed dual LCSTs with both segments revealing distinctive CPTs (at 75 and 37 °C for poly(MPAM) and poly(DEAAM) blocks, respectively) by both UV–Vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 59–67     

PPV Polymerization through the Gilch Route: Diradical Character of Monomers

Despite various studies on the polymerization of poly(p‐phenylene vinylene) (PPV) through different precursor routes, detailed mechanistic knowledge on the individual reaction steps and intermediates is still incomplete. The present study aims to gain more insight into the radical polymerization of PPV through the Gilch route. The initial steps of the polymerization involve the formation of a p‐quinodimethane intermediate, which spontaneously self‐initiates through a dimerization process leading to the formation of diradical species; chain propagation ensues on both sides of the diradical or chain termination occurs by the formation of side products, such as [2.2]paracyclophanes. Furthermore, different p‐quinodimethane systems were assessed with respect to the size of their aromatic core as well as the presence of heteroatoms in/on the conjugated system. The nature of the aromatic core and the specific substituents alter the electronic structure of the p‐quinodimethane monomers, affecting the mechanism of polymerization. The diradical character of the monomers has been investigated with several advanced methodologies, such as spin‐projected UHF, CASSCF, CASPT2, and DMRG calculations. It was shown that larger aromatic cores led to a higher diradical character in the monomers, which in turn is proposed to cause rapid initiation.     

Graphene Quantum Dots Assembled with Metalloporphyrins for “Turn on” Sensing of Hydrogen Peroxide and Glucose

Noncovalent and multifunctional hybrids have been generated via π–π stacking and electrostatic interactions by combining the nanometer‐scale graphene structure of graphene quantum dots (GQDs) with Fe^III 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridyl)porphine (FeTMPyP). The inner filter effect (IFE) of FeTMPyP on the GQDs results in substantial PL quenching of the GQDs. The quenched PL of GQDs by the FeTMPyP can be switched back “on” in response to the reaction between FeTMPyP and H₂O₂, which causes rupture of the cyclic tetrapyrrolic nucleus with consequential loss of iron from FeTMPyP, and then proceeds further to produce colorless dipyrroles and monopyrroles. This “turn on” system can be applied for simple and convenient H₂O₂ sensing and can be further extended to the detection of glucose in combination with the specific catalytic effect of glucose oxidase (GOx) through the oxidation of glucose and formation of H₂O₂. Because of the inherent synthetic control available for the design of metalloporphyrins, the GQDs‐based optical sensing approach described here has the potential to be highly versatile for other target analytes.     

Cyclotetrabenzoin: Facile Synthesis of a Shape‐Persistent Molecular Square and Its Assembly into Hydrogen‐Bonded Nanotubes

Cyanide‐catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square‐shaped macrocycle ornamented with four α‐hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.9 Å. In the solid state, these functional groups extensively hydrogen bond, resulting in a microporous three‐dimensional organic framework with one‐dimensional nanotube channels. This material exhibits permanent—albeit low‐porosity, with a Langmuir surface area of 52 m² g^?1. Cyclotetrabenzoin’s easy and inexpensive synthesis and purification may inspire the creation of other shape‐persistent macrocycles and porous molecular crystals by benzoin condensation.     

超分子水凝胶作为胰岛素缓释体系的研究

利用α-环糊精(α-CD)与含有聚乙二醇(PEG)链段的聚合物Pluronic F127的超分子作用制备水凝胶.该物理交联水凝胶的交联点包括α-CD与PEG链包合物堆积形成的微晶区和聚合物疏水链段聚集区.优化水凝胶组分,得到具有较低固含量和较短凝胶化时间的体系用于胰岛素的负载和释放研究.通过X射线衍射(XRD),扫描显微镜(SEM)对水凝胶结构进行表征.通过紫外分光光度计监测胰岛素的释放过程,结果表明,水凝胶释药时间约为65 h,且释放曲线较为平缓.细胞毒性实验结果表明该水凝胶材料对细胞生长无明显抑制作用.小鼠体内释药实验结果表明该水凝胶载体对延长胰岛素的释药时间有一定效果,可作为多肽类药物的缓释体系.     

Two-dimensional correlation analysis of continuous online in situ ATR-FTIR on the adsorption of butyl xanthate at the surface of a-PbO

The adsorption behavior of butyl xanthate on the surface of lead oxide was investigated using continuous online in situ attenuated total reflectance Fourier transform infrared（ATR-FTIR） spectroscopy technique and two dimensional（2D） correlation analysis.The adsorbed layer studied was prepared by coating α-PbO particles onto the surfaces of the ZnSe crystal.The appearance of spectral peaks at 1203 cm^-1,1033 cm^-1 and their red shift indicated the formation and aggregation of xanthate at the surface of α-PbO.According to 1R intensity changes after rinsing with deionized water and a NaOH solution,the adsorption was proved to be a chemisorption type.The competition between xanthate and OH for the surfaces leads to desorption of xanthate at higher pH.The technique of 2D correlation ATR-FTIR spectroscopy was used to evaluate the changing order of spectral intensities in the adsorption process,and the results indicated that xanthate micelles were formed at the surfaces.The adsorption kinetics of butyl xanthate was found to be a pseudo-second-order reaction model and the adsorption capacity of butyl xanthate at α-PbO was as high as 281 mg g^-1 after 150 min.     

刺五加叶黄酮脂质体和滴丸的药动学差异比较

采用液质联用(LC-MS/MS)方法,分析刺五加叶黄酮脂质体、刺五加叶滴丸和刺五加叶黄酮提取物经大鼠灌胃给药后其主要成分金丝桃苷的药代动力学和生物利用度,考察刺五加叶黄酮的适宜剂型。用PKsolver软件进行药代动力学数据处理,大鼠灌胃刺五加叶黄酮提取物、刺五加叶滴丸和刺五加叶黄酮脂质体后测得金丝桃苷的最大血药浓度(C_(max))分别为(210.24±10.3)、(254.12±9.2)、(349.34±12.5)μg/L;0~t时间内药时曲线面积(AUC_(0-t))分别为(30.7±2.7)、(35.01±1.98)、(45.2±2.8)μg/(m L·min);平均驻留时间(MRT)分别为(334.42±75.36)、(394.56±90.26)和(640.35±84.26)min。结果表明,刺五加叶黄酮脂质体血药达峰浓度增加,清除速率降低,药时曲线下面积加大,生物利用度显著提高,脂质体有望成为刺五加叶黄酮的适宜剂型。     

Influence of selected mobile phase properties on the TLC retention behavior of ziprasidone and its impurities

ABSTRACT

Influence of nine different solvents, either alone or in a mixture, on the retention behavior of ziprasidone and its five impurities were examined by normal-phase thin-layer chromatography. Migration distances of the examined compounds obtained under the examined chromatographic conditions were correlated with calculated mobile phase properties, such as Snyder polarity and Hansen solubility. Linear or second-order polynomial relationships with high correlation coefficients were established between investigated variables. The obtained mathematical functions and statistical results indicated that selected mobile phase properties can be used for the prediction of the retention behavior of ziprasidone and its five impurities.