Selenylation Modification of Degraded Polysaccharide from Enteromorpha prolifera and Its Biological Activities

Polysaccharide extracted from Enteromorpha prolifera possessed excellent biological activities,but its molecular weight was greatly high which influenced the activity.Organic Se had higher biological activities and was safer than inorganic Se species.In the present study,Enteromorpha polysaccharide was degraded to low molecular weight by free-radical degradation method of H_2O_2 and ascorbic acid.By single factor and orthogonal experiments,the optimal degradation conditions were reaction time of 2 h,reaction temperature of 50℃,H_2O_2/ascorbic acid(n/n=1:1)concentration of 15 mmol L^(-1),and solid-liquid ratio of 1:50(g mL^(-1)).Then,the degraded polysaccharide was chemically modified to obtain its selenide derivatives by nitric acid-sodium selenite method.The selenium content was 1137.29μg g^(-1),while the content of sulfate radical had no change.IR spectra indicated that the selenite ester group was formed.Degraded polysaccharide selenide was characterized and evaluated for antioxidant,antifungal and antibacterial activities.The results showed that degraded polysaccharide selenide had strong capacity of scavenging DPPH and·OH free radical.It had significant antibacterial properties for Escherichia coli,Bacillus subtilis and Salmonella spp.,and it also had significant antifungal properties for Apple anthrax.The result ascertained degradation and selenylation modification did not change the main structure of polysaccharides.It was possible that free-radical degradation was an effective way for enhancing antioxidant activity to decrease molecular weight of polysaccharides.

Visible-Light-Promoted Palladium-Catalyzed Cross-Coupling of lodocarboranes with Disulfides and Phenylselenyl Chloride

This work describes a general method for the synthesis of a series of sulfenylated and selenylated carboranes at room temperature using readily available iodocarboranes as starting materials via boron-centered carboranyl radicals.Such hypervalent boron radicals are generated by a visible-light-promoted Pd(O)/Pd(I)pathway.They are useful intermediates and can be trapped by disulfides and phenylselenyl chloride for the convenient construction of B-S/Sebonds.

Chemoselective electrochemical seleno-cyclization of dienes to medium-sized benzo[b]azocines

The preparation of medium-sized benzo[b]azocines has always been challenging because of inherently unfavorable enthalpy and entropy factors.This report presents a novel approach for accessing 8-membered seleno-benzo[b]azocines via electrochemically-driven seleno-cyclization.This method enables room-temperature preparation of various structurally diverse medium-sized seleno-benzo[b]azocines.The facile deselenation of the seleno-cyclization products to generate functionalized dienes is an additional benefit of this indispensable reaction.Mechanistic insights are presented based on radical inhibition experiments and cyclic voltammetry measurements,which elucidate the radical pathway.Finally,density functional theory calculations further rationalize the rate-determining step and the unique chemoselectivity observed in this transformation.

Regioselective electrochemical radical cascade cyclization of internal alkynes to selenated and trifluoromethylated dihydropyran

Dihydropyran(DHP)compounds are not only found in natural products and bioactive molecules,but also serve as important precursors in organic synthesis.Nonetheless,traditional methods for the construction of such compounds are usually limited to disubstituted DHPs.To address this synthetic challenge,reported here is an efficient electrochemical strategy toward the selenated and trifluoromethylated DHP compounds.The reaction proceeded smoothly under mild electrolysis conditions.The broad substrate scope(>50 examples)and scalable synthesis demonstrated the complexity-building potential of the strategy.Initial mechanistic studies reveal that cyclization may involve a radical process.This protocol may promote the further development of diversified synthesis of multi-substituted dihydropyran.

在水系锌电池中通过孔相双调控实现碳纳米管@硒化镍的快速动力学活化

金属硫系化合物作为水相锌电池的高性能阴极具有很大的潜力.然而,低可达表面和剧烈的体积膨胀限制了其整体性能和实际应用.为此,采用相工程策略结合空心结构设计,调控OH−在电极表面的吸附/脱附,能显著提高电极的整体电化学性能.本研究首次利用Se@C纳米棒模板,通过原位硒化过程可控合成了一系列碳纳米管(CNT)负载的镍硒化物,包括立方型NiSe_(2)NiSe_(2)/Ni_(0.85)Se复合材料、六方型Ni_(0.85)Se.优化后的NiSe_(2)/Ni_(0.85)Se/CNT复合材料具有比表面积大、孔隙率高、碳骨架空心等优点,具有616Cg^(−1)的高比容量、优良的倍率性能和稳定的循环寿命.通过一系列的非原位表征和DFT计算,深入研究了其内部的法拉第机制.结果表明,所制备的Ni//Zn电池在3485 W kg^(−1)时具有311.4 W h kg^(−1)的高能量密度和较长的循环寿命.本研究为硒化镍基电极材料的设计提供了一种巧妙的策略,且深入研究了其在碱性锌电池中的法拉第机理.

Practical and sustainable approach for clean preparation of 5-organylselanyl uracils

An eco-friendly,sustainable and practical method for the efficient preparation of 5-organylselanyl uracils through the electrochemical selenylation of uracils and dio rganyl diselenides at room temperature under oxidant-and external electrolvte-free conditions was developed.

Controllable Construction of Vinyl Sulfones and β-Keto Selenosulfones via Selective Oxidative Sulfonylation of Alkenes

Comprehensive Summary The selective oxidative sulfonylation of alkenes with selenium sulfonate depended on the reaction conditions.The electrochemical C—H sulfonylation proceeded smoothly to afford(E)-vinyl sulfones with good selectivity in an undivided cell without external oxidant.While aerobic trifunctionalization of alkenes occurred in the presence of KI in the air,which providesβ-keto selenosulfones via the formation of C—O,C—S,and C—Se bonds in one-pot.Following control experiments,a plausible mechanism is proposed to rationalize the experimental results.