A new polysaccharide was isolated from the culture of Acetobacter aceti subsp. xylinum (A. xylinum) NCI 1005 grown on sucrose. The structure of the polymer was analyzed by nuclear magnetic resonance (NMR) spectroscopy. The water-soluble polysaccharide (WSP) was determined to be β(2, 6) linked polyfructan, which was structurally different from the polymer synthesized from glucose instead of sucrose by the same strain. The discovery of the new polysaccharide has elucidated that the bacterium has the ability to synthesize two different kinds of water-soluble polysaccharides. 相似文献
Two-dimensional C-H correlation NMR spectra are presented for the native cellulose types Iα and Iβ from Cladophora sp. A remarkable difference of correlation peaks between Iα and Iβ was observed, which indicates an essential structure difference between the two types of native cellulose. 相似文献
Iridium complexes having a pincer‐type gallylene ligand were successfully synthesized utilizing bis(phosphino)terpyridine as an efficient scaffold for the Ir?GaI bond. The stabilization of the gallylene moiety by the pincer‐type structure enabled various reactions at Ir with keeping the gallylene ligand intact, leading to unique structures and reactivities of PGaIP?Ir complexes. 相似文献
Synthesis of arylboronates via borylation of C–C σ-bonds of aryl ketones was achieved by the combined use of photoenergy and a Rh catalyst. The cooperative system enables α-cleavage of photoexcited ketones to generate aroyl radicals via the Norrish type I reaction, which are successively decarbonylated and borylated with the rhodium catalyst. This work establishes a new catalytic cycle merging the Norrish type I reaction and Rh catalysis and demonstrates the new synthetic utility of aryl ketones as aryl sources for intermolecular arylation reactions.Synthesis of arylboronates via borylation of C–C σ-bonds of aryl ketones was achieved by the combined use of photoenergy and a Rh catalyst.相似文献
Development of facile and versatile synthetic tools for decorating π-conjugated molecules has attracted considerable interest because of their potential application in creating novel functional π-systems. Reported herein are quantitative catalyst-free hydroamination reactions of a series of aromatic diimide compounds having vinyl groups at the π-core, which have been confirmed by NMR, UV-vis absorption spectroscopy, mass analysis, and single-crystal X-ray structural analysis. Kinetic studies revealed that the hydroamination reaction of a vinyl-substituted naphthalenediimide with an aliphatic amine proceeded rapidly under benign conditions. Similarly, the two vinyl groups attached to aromatic diimides reacted with amines simultaneously, resulting in the formation of amine bisadducts and macromolecules. An amino group appended perylenediimide through an ethylene spacer at the π-core exhibited distinct fluorescence switching in response to acid and base. 相似文献
Supramolecular photocatalysis via charge-transfer excitation of a host–guest complex was developed by use of the macrocyclic boronic ester [2+2]BTH-F containing highly electron-deficient difluorobenzothiadiazole moieties. In the presence of a catalytic amount of [2+2]BTH-F, the triplet excited state of anthracene was generated from the charge-transfer excited state of anthracene@[2+2]BTH-F by visible-light irradiation, and cycloaddition of the excited anthracene with several dienes and alkenes proceeded in a [4+2] manner in high yields. 相似文献
Guest-controlled diastereoselective self-assembly of a diboryltellurophene and a chiral tetrol bearing an indacene backbone was achieved to give either hetero- or homochiral macrocyclic boronic esters, selectively. The heterochiral isomer (hetero-[2+2]Te) exhibited a higher inclusion ability for electron-deficient aromatic guests, leading to effective quenching of phosphorescence from the diboryltellurophene moieties. The reported macrocycles collectively represent a promising arene sensing approach based on phosphorescence. 相似文献
An unprecedented photo-promoted skeletal rearrangement reaction of phosphine–borane frustrated Lewis pairs, o-(borylaryl)phosphines, involving cleavage of an unstrained sp2C–sp3C σ-bond is reported. The reaction realizes an efficient synthesis of cyclic phosphonium borate compounds. The reaction mechanism via a boranorcaradiene intermediate is proposed based on theoretical calculations. This work sheds light on the new photoreactivity of phosphine–borane FLPs. 相似文献
π–π assisted : Photoinduced electron transfer from cofacial porphyrin dimers to electron acceptors is prominently accelerated, whereas the back electron transfer is decelerated, relative to the corresponding porphyrin monomer (see figure).