Synthesis,Photophysical Properties of Tribranched Chromophores Based on 1,3,5‐Triazine Core and Different Electro‐donating End‐groups

Three two‐photon absorption (TPA) tribranched chromophores were successfully prepared, in which 1,3,5‐triazine is been as electron deficient core, 1,4‐phenylenedivinylene as conjugated bridge, 3,4‐ethylenedioxythiophene (EDOT) ( T1 ), N‐methylpyrrole ( T2 ) or triphenylamine ( T3 ) as electron‐donating end‐groups. Their photophysical properties were studied by absorption, one‐ and two‐photon fluorescence and TPA cross‐section determination. The nonlinear transmission (NLT) measurement in femtoseconds (fs) regime at 800 nm indicates that TPA cross‐section (₂ values of T1 , T2 and T3 with extended Π‐conjugated bridge are much larger than the corresponding chromophore T4 with a short length bridge, and TPA cross‐section of T1 with end‐groups EDOT exhibits a remarkable enhancement compared with T2 and T3 having the same length Π‐system. The chromophores T1 , T2 and T3 show also remarkable up‐converted luminescence and optical limiting activity.     

空间高层大气遥感远紫外成像光谱仪的光学系统

空间高层大气遥感远紫外成像光谱仪主要用于观测高层大气中的远紫外辐射和实现对其内部中尺度现象成像的功能。目前我国该类的相关仪器研究基础还比较薄弱,针对这种情况,在光学系统设计的角度上给出了一种适用于130～180nm波段探测的光学系统方案。该成像光谱仪光学系统以离轴抛物镜为物镜,串联Wadsworth结构为成像光谱系统;这种串联Wadsworth成像光谱系统采用离轴抛物镜做准直镜,分光器件为平面光栅和球面光栅串联,实现二次色散,同时球面光栅起到聚焦成像作用;在像差理论的基础上,对该结构的光程函数和各像差进行了分析,获得了改进结构的宽波段完善成像条件。针对低轨空间探测应用要求设计了相关改进型Wadsworth结构成像光谱仪光学系统,设计结果证明系统像差得到了充分校正,在奈奎斯特频率(20lp/mm)下全视场全波段调制传递函数值在0.6以上。该优化结构同时具备高空间分辨率和高光谱分辨率,性能优越。     

An overview on synthetic strategies to coumarins

Coumarins units have recently emerged as a hot topic of research due to their diverse applications. Their synthesis is partly based on classical methodologies such as Pechmann reaction or Knoevenagel condensation, but it also sparked the discovery of completely new pathways. In very recent years so-called vertically expanded coumarins were synthesized, effectively expanding the portfolio of existing architectures. This review serves as a guide through synthesis strategies to coumarins.     

Synthesis and photophysical properties of benzo[c]thiophene,p-phenylene-, triphenylamine-, and pyrene-based vinylenes

An efficient synthesis of benzo[c]thiophenyl/p-phenylenyl/pyrenyl phosphonate esters has been achieved using ZnBr₂-catalyzed Michaelis–Arbuzov reaction of corresponding benzyl alcohol/bromides at room temperature. Horner–Wadsworth–Emmons reaction of the phosphonate esters with aryl/heteroaryl aldehydes in the presence of t-BuOK furnished the vinylenes in good yields. The absorption and emission characteristics of the synthesized vinylenes were also reported.     

Synthesis of a Thiophene‐Based Nonlinear Optical Chromophore

This report details an eight‐step synthesis of the thiophene‐type nonlinear optical chromophore 1 in 38% overall yield. Only one early step required chromatography.     

An Efficient Approach to the Synthesis of Ethyl α-Cyanoalkyl β-Substituted Acrylates by the HWE Olefination of Ethyl 2-(Diethoxyphosphoryl) Cyanoalkanoates

Ethyl α-cyanoalkyl β-substituted acrylates 5a–i were prepared in good yields on a synthetic scale by Horner–Wadsworth–Emmons olefination of the corresponding ethyl 2-(diethoxy-phosphoryl) cyanoalkanoates 3a–c using different aldehydes and anhydrous potassium carbonate in dry THF at reflux.     

Z- and E-selective Horner–Wadsworth–Emmons reactions

In the present work, we determined and evaluated the stereochemical outcome of the Horner–Wadsworth–Emmons (HWE) reaction of 2-oxoalkylphosphonates with different ester functions (bis(2,2,2-trifluoroethyl), 2,2,2-trifluoroethyl methyl, dimethyl) and side chains (aliphatic, aromatic) with three different aldehydes (benzaldehyde, THP- and PPB-protected Corey aldehydes) under two reaction conditions. The “trans” protocol is generally used in the E-selective HWE reactions, while “cis” protocol promotes the Z-selectivity.     

First mechanosynthesis of piperlotines A,C, and derivatives through solvent-free Horner–Wadsworth–Emmons reaction

Piperlotines are natural products characterized by an α,β-unsaturated amide moiety. These compounds found wide applications in Medicinal Chemistry like antibacterials, cytotoxic agents, anticoagulants, among others. To date, diverse methods of synthesis have been reported for piperlotines, but involving the use of catalysts, hazard reagents, anhydrous media or coupling reagents. Thus, in this work, we developed a greener method of synthesis of piperlotines A, C, and derivatives, through mechanochemical activation under solvent-free conditions. The reaction of a β-amidophosphonate, K₂CO₃, and an aromatic aldehyde afforded target compounds in moderate to good yields (46–77%), in an open atmosphere by grinding. It is worth to mention that this mechanochemical process was under thermodynamic control because just E isomer was isolated for every reaction. Moreover, synthesized piperlotines have been predicted by means of chemoinformatic analysis as potential therapeutic agents for the treatment of arthritis or cancer.     

A rapid ultrasound-promoted Horner–Wadsworth–Emmons reaction for the preparation of ferrocene derivatives. Application to ferrocene-modified ITO electrodes

The Horner–Wadsworth–Emmons reaction of ferrocenecarboxaldehyde with various phosphonate-stabilized carbanions has been performed under ultrasound irradiation. The reaction time at ambient temperature was considerably shortened (5–15 min) compared to nonsonicated conditions requiring often refluxing for 6–24 h. Control of the reaction time can be achieved by tuning the base strength in different solvents. This method was successfully applied to the preparation of various 2-substituted vinylferrocenes. The as-prepared (E)-2-ferrocenylvinylphosphonic acid was used to modify ITO electrodes to form redox-active functionalized ITO electrodes which have been characterized by means of electrochemical techniques.     

Synthesis of the FG ring fragment of pectenotoxins 1-9

The synthesis of the FG ring fragment common to pectenotoxins 1-9 is reported. The successful, convergent synthesis relied on high yielding routes to access two key intermediates; aldehyde 1 and phosphonium salt 2. A Z-selective Wittig reaction gave access to advanced linear precursor 3, which was converted to FG ring fragment 4 using two sequential cyclization reactions.