Synthesis of readily recyclable biobased plastics by Diels-Alder reaction

Readily recyclable biobased plastics were designed and synthesized utilizing the thermally reversible DA reaction. Furyl-telechelic poly(butylene succinate) prepolymers (PBSF(2)) were extended with bis- and tris-maleimide linkers (M(2) and M(3)) by the DA reaction in the bulk state to produce linear and network polymers, respectively. The DA reaction was able to proceed at 25-80 degrees C, at which crystalline domains of PBSF(2) were present. In the linear polymer system, the molecular weight in the reaction equilibrium was dependent on the chain length of the prepolymer, but almost independent of the reaction temperature. The cycle of DA and retro-DA reactions was repeatable with no prepolymer deterioration.     

Reaction of 6‐aryl‐ or styryl‐4‐methylsulfanyl‐2‐oxo‐2H‐pyrans with active methylene compounds and fluorescence properties of the products

New 2‐pyrone derivatives, dialkyl 3‐cyano‐6‐phenyl‐2‐oxo‐2H‐pyran‐4‐ylmalonates and alkyl 3‐cyano‐6‐phenyl‐2‐oxo‐2H‐pyran‐4‐ylacetates, which were easily prepared by the reaction of 6‐aryl‐4‐methyl‐sulfanyl‐2‐oxo‐2H‐pyran‐3‐carbonitriles with active methylene compounds in the presence of potassium carbonate, show fluorescence emission radiation. The light‐emitting region of dimethyl 3‐cyano‐6‐(4‐N,N‐dimethylamino)styryl‐2‐oxo‐2H‐pyran‐4‐ylmalonate ( 7h ) was 620 nm in dichloromethane, making this compound a typical red fluorescent compound. Methyl 8‐hydroxy‐6‐methyl‐1‐oxo‐3‐phenyl‐1H‐pyrano‐[3,4‐c]pyridine‐5‐carboxylate deriv‐atives also showed fluorescence in the solid state. This is the first example of fluorescence in fused 2‐pyrone derivatives.     

New C(28) steroidal glycosides from Tubocapsicum anomalum

Two new C(28) steroidal glycosides, tuboanosides A (1) and B (2), were isolated from the fruit of Tubocapsicum anomalum MAKINO. Their chemical structures were elucidated on the basis of spectroscopic and X-ray diffraction analysis of the p-bromobenzoyl derivative (4) of tuboanosigenin (3), the sapogenol derivative of these two glycosides. Tuboanosides have the structural peculiarity of an unusual side chain carrying an unusual linkage with a C-21 bound to C-25 on the lactone ring.     

Two new dimeric coumarins isolated from Murraya exotica

Bismurrangatin and murramarin A, two new coumarins, were isolated from the vegetative branches of Murraya exotica. Murramarin A is a rare type of bicoumarin that connects two coumarin moieties by orthoester structure. The structures were elucidated based on spectroscopic methods, especially by 2D-NMR experiments.     

Intramolecular cyclotrimerization of triynes catalyzed by N-heterocyclic carbene-CoCl2/Zn or -FeCl3/Zn

[reaction: see text] Triynes 1 could effectively be cyclotrimerized to annulated benzenes 2 by treatment with a catalytic amount of zinc powder, N-heterocyclic carbene, and CoCl(2) or FeCl(3).     

Photochemical reactions of β-aminovinyl aryl thioketones

Irradiation of β-aminovinyl aryl thioketones ( 1a-b ) afforded β-aminovinyl aryl ketones ( 2a-b ). 2H-Thiopyran derivatives ( 4a-b ) were obtained when β-aminovinyl phenyl thioketone ( 1a ) was irradiated with methyl acrylate and acrylonitrile. 4H-Thiopyran derivatives ( 6,8 ) were also obtained thermally in the reaction of β-aminovinyl phenyl thioketone ( 1a ) and methyl propiolate and maleic anhydride.     

Multispectral optical imaging combined in situ with XPS or ToFSIMS and principal component analysis

All X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) instruments have optical cameras to image the specimen under analysis, and often to image the sample holder as it enters the system too. These cameras help the user find the appropriate points for analysis of specimens. However they seldom give as good images as stand‐alone bench optical microscopes, because of the limited geometry, source/analyser solid angle and ultra‐high‐vacuum (UHV) design compromises. This often means that the images displayed to the user necessarily have low contrast, low resolution and poor depth‐of‐field. To help identify the different regions of the samples present we have found it useful to perform multispectral imaging by illuminating the sample with narrow‐wavelength‐range light emitting diodes (LEDs). By taking an image under the illumination of these LEDs in turn, each at a successively longer wavelength, one can build up a set of registered images that contain more information than a simple Red–Green–Blue image under white‐light illumination. We show that this type of multispectral imaging is easy and inexpensive to fit to common XPS and ToF‐SIMS instruments, using LEDs that are widely available. In our system we typically use 14 LEDs including one emitting in the ultraviolet (so as to allow fluorescent imaging) and three in the near infra‐red. The design considerations of this system are discussed in detail, including the design of the drive and control electronics, and three practical examples are presented where this multispectral imaging was extremely useful. Copyright © 2016 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.     

Automated precolumn derivatization system for analyzing physiological amino acids by liquid chromatography/mass spectrometry

An automated method for high‐throughput amino acid analysis, using precolumn derivatization high‐performance liquid chromatography/electrospray mass spectrometry (HPLC/ESI‐MS), was developed and evaluated. The precolumn derivatization step was performed in the reaction port of a home‐built auto‐sampler system. Amino acids were derivatized with 3‐aminopyridyl‐N‐hydroxysuccinimidyl carbamate, and a 3 μm Wakosil‐II 3C8‐100HG column (100 × 2.1 mm i.d.) was used for separation. To achieve a 13 min cycle for each sample, the derivatization and separation steps were performed in parallel. The results of the method evaluation, including the linearity, and the intra‐ and inter‐precision, were sufficient to measure physiological amino acids in human plasma samples. The relative standard deviations of typical amino acids in actual human plasma samples were below 10%. Copyright © 2009 John Wiley & Sons, Ltd.     

Solvent-free synthesis of azulene derivatives via Passerini reaction by grinding

An efficient and convenient approach to the synthesis of azulene derivatives bearing a carboxamide unit based on solvent-free Passerini reaction, using grinding is described. This method provides several advantages such as high efficiency, operational simplicity, and mild conditions.