Copper-catalyzed oxidative coupling of carboxylic acids with formamides for the synthesis of α,β-unsaturated amides

A novel and efficient protocol for the synthesis of α,β-unsaturated amides has been developed using catalytic amount of Cu(OAc)₂ and TBHP as an available oxidant. Oxidative coupling of various unsaturated carboxylic acids with N,N-disubstituted formamides was examined to furnish the desired products in good yields.     

Adsorption Mechanism of Comb Polymer Dispersants at the Cement/Water Interface

Comb polymers are commonly used as dispersants to stabilize highly concentrated cement suspensions. The effectiveness of such polymeric additives to stabilize these suspensions is determined to a large extent by the amount adsorbed. In this study we investigated the adsorption characteristics of various comb dispersant containing different graft densities on surfaces of cement particle. The effect of inorganic salts on their adsorption was also examined in order to elucidate their adsorption mechanism. The results show that the adsorption of comb polymer dispersants on cement surface conforms approximately to Langmuir's adsorption isotherm and the characteristic plateau A _s and adsorption free energy ΔG_ads are largely dependent on the anionic group content of the comb polymers. The A _s and ΔG_ads increase with increasing anionic group content. This information suggests that the adsorption of comb polymers on cement surfaces is dominated by electrostatic interaction between COO-groups on the comb polymers and the positive surface of the cement. This conclusion is supported by effects of inorganics such as calcium and sulfate ions, and diffuse reflectance FTIR spectroscopy. The implication of results for tuning polymers for the required performance in cement manufacture should be noted.     

氧杂环丁烷系列含能粘合剂的合成研究进展

新型含能粘合剂的出现进一步提高了固体推进剂的能量和性能。其中,在3-位取代含能基团实现氧杂环丁烷的含能化并以此类单体合成的含能粘合剂,由于其具有相对分子量和官能度可控性好、多分散性和玻璃化转变温度低而受到重视,引起广泛关注。     

Vibrational spectra of a ferrocenyl phosphine derivative chemisorbed on 3-aminopropylsilyl modified silica gel

Samples of silica gel dried at different temperatures, silica gel modified with 3-aminopropylsilyl (APS) and silica gel modified with APS and further with a ferrocenyl phosphine derivative were investigated by DRIFT, transmission FTIR and MicroRaman spectroscopy. The reaction between 3-aminopropyltrimethoxysilane (APTMS) and silica gel was mainly identified by the diminishing or vanishing intensity of the stretching band of the free OH groups in the silica gel. Further chemical reaction of the APS groups with a ferrocenyl phosphine derivative (suitable as ligand in homogeneous catalysis) was identified in the IR spectra by the appearance of the CN stretching band of the formed Schiff base, and diminishing intensity of the δ(NH₂) modes. According to the IR spectra the reaction of the ferrocenyl phosphine derivative with the APS-modified silica gel is almost quantitative. From the recorded IR and Raman spectra, conclusions concerning the substitution of APTMS methoxy groups during the chemisorption on silica gel were derived. Through deconvolution of the complex Raman band in the siloxy stretching region of the APS-modified silica gel, the newly formed siloxy bond was identified.     

表面官能团化增强碳纳米笼超级电容器性能

以具有多级孔结构、高比表面积、良好导电性等特征的碳纳米笼（CNCs）为前体,采用硝酸氧化法在CNCs表面引入含氧官能团。以CNCs为超级电容器电极材料,在相同电流密度下,官能团化样品的比电容显著高于纯CNCs;在1A·g^-1下比电容最高可达到255F·g^-1,比纯CNCs的188F·g^-1增加了34%,这表明表面含氧官能团化能够显著提高CNCs的超级电容器比电容。在100A·g^-1的大电流密度下,硝酸氧化后CNCs的比电容保持在111~167F·g^-1,表明具有良好的耐大电流充放电性能。在10A·g^-1的电流密度下循环10000圈后,CNC-6M样品的比电容由196F·g^-1下降到176F·g^-1,样品的比电容仍保留90%,具有良好的循环稳定性。表面含氧官能团化CNCs所表现出的这种优异的超级电容器性能归因于CNCs的多尺度分级孔结构、高比表面积、良好的导电性、表面亲水性含氧官能团化带来的浸润性提高和引入的赝电容。     

Direct α-alkylation of ketones with primary alcohols catalyzed by iridium–CNP complex

The α-alkylation of ketones with primary alcohols was realized by CC cross-coupling with iridium–CNP complexes as catalyst. This reaction proceeds via dehydrogenation reactions, aldol condensation, and hydrogenation using the borrowed hydrogen atoms from alcohols. The pyridyl methanols and other heterocyclic substituted methanols, especially alkyl alcohols, were also suitable for this transformation.     

Enantioselective sulfenylation of α-nitroesters catalyzed by diarylprolinols

The organocatalytic sulfenylation of α-nitroesters mediated by diaryl-l-prolinols was developed. A range of α-sulfenylated α-nitroesters were obtained in good yields with moderate to good enantioselectivities.     

When C–H bond functionalization meets visible-light photoredox catalysis

In recent years, visible-light-mediated C–H bond functionalization has become an emerging field at the forefront of organic synthesis. It is of considerable interest to academic and industrial chemists owing to the atom/step economical features as well as the overall sustainability. In this Letter, we mainly discussed the recent typical examples in sp² and sp³ C–H bond functionalization by means of visible-light photoredox catalysis.     

基于柱[n]芳烃(准)轮烷的研究进展

柱芳烃作为一类新型的大环主体分子,自2008年首次报道以来,引起了人们,特别是化学家的广泛关注.目前,它已在分子识别、(准)轮烷、超分子聚合物、分子弹簧、智能跨膜离子通道、囊泡、金属有机骨架结构等众多研究领域作为重要模块得到初步的应用.主要将以柱芳烃作为主体大环分子来构筑(准)轮烷的研究进展进行简要的综述,同时还介绍了基于柱芳烃的(准)聚轮烷的研究概况,并对未来的发展作了进一步展望.