Ionic liquid [Hmim]HSO4-promoted one-pot oxidative conjugate addition of sulfur-centred nucleophiles to Baylis-Hillman adducts

The first example of the one-pot oxidative conjugate addition of sulfur-centred nucleophiles to Baylis-Hillman adducts is reported. The reaction involves oxidation of Baylis-Hillman adducts with NaNO₃ in the Brønsted acidic ionic liquid [Hmim]HSO₄ to give [E]-α-cyanocinnamaldehydes followed by conjugate hydrothiocyanation/hydrosulfenylation with NH₄SCN/PhSH to afford the corresponding β-thiocyanato (or β-phenylsulfenyl)-α-cyanohydrocinnamaldehydes diastereoselectively in 76-89% yields in a one-pot procedure. After isolation of the product, the ionic liquid [Hmim]HSO₄ could be easily recycled for further use.     

Tandem enantioselective conjugate addition-Mannich reactions: efficient multicomponent assembly of dialkylzincs, cyclic enones and chiral N-sulfinimines

A convenient access to enantiopure β-amino ketones through a multicomponent reaction of dialkyl zinc reagents, cyclic enones and chiral N-tert-butanesulfinimines is disclosed. Four diastereoisomers can be selectively obtained by the appropriate choice of the chiral ligand (L or ent-L) and the chiral N-sulfinimine (R_S or S_S). The protocol is particularly efficient when enolisable N-sulfinimines are used.     

Bifunctional Iminophosphorane-Catalyzed Enantioselective Nitroalkane Addition to Unactivated α,β-Unsaturated Esters**

Herein we describe the enantioselective intermolecular conjugate addition of nitroalkanes to unactivated α,β-unsaturated esters, catalyzed by a bifunctional iminophosphorane (BIMP) superbase. The transformation provides the most direct access to pharmaceutically relevant enantioenriched γ-nitroesters, utilizing feedstock chemicals, with unprecedented selectivity. The methodology exhibits a broad substrate scope, including β-(fluoro)alkyl, aryl and heteroaryl substituted electrophiles, and was successfully applied on a gram scale with reduced catalyst loading, and, additionally, catalyst recovery was carried out. The formal synthesis of a range of drug molecules, and an enantioselective synthesis of (S)-rolipram were achieved. Additionally, computational studies revealed key reaction intermediates and transition state structures, and provided rationale for high enantioselectivities, in good agreement with experimental results.     

Stereodivergent Construction of 1,3-Chiral Centers via Tandem Asymmetric Conjugate Addition and Allylic Substitution Reaction

Herein, we report a synthesis of cyclohexanones bearing multi-continuous stereocenters by combining copper-catalyzed asymmetric conjugate addition of dialkylzinc reagents to cyclic enones with iridium-catalyzed asymmetric allylic substitution reaction. Good to excellent yields, diastereoselectivity and enantioselectivity can be obtained. Unlike the stereodivergent construction of adjacent stereocenters (1,2-position) reported in the literature, the current reaction can achieve the stereodivergent construction of nonadjacent stereocenters (1,3-position) by a proper combination of two chiral catalysts with different enantiomers.     

基于分子内旋转受限原理的线性共轭小分子的AIE性能研究

研究了6个线性共轭化合物4-丁基联苯(L1)、4,4’-二异丙基联苯(L2)、5,5’-二甲基-2,2’-联吡啶(L3)、2-([1,1’-联苯]-4-)噻吩(L4)、1,1’-联萘(L5)和5-苯基-2,2’-联噻吩(L6)的紫外-可见光谱和荧光发射光谱。结果表明,化合物L1、L2和L3均具有聚集诱导发光(AIE)性能,化合物L4、L5和L6则不具有AIE性能。该研究结果表明,二联苯(或两个简单芳杂环相连)系列化合物具有AIE性能,分子内旋转受限(RIR)是该系化合物产生AIE现象的机理。但是在二联苯的结构基础上继续增加链的长度,或者引入体积更大的芳环(萘环),化合物不再具有AIE性能。     

共轭微孔聚合物及其复合材料的制备及应用

共轭微孔聚合物是一类具有扩展共轭体系的骨架材料,具有比表面积大、稳定性高、微孔大小和体积可精确调控等特点。由于其独特的结构特点,共轭微孔聚合物在各方面展现出巨大的应用潜力,本文综述了共轭微孔聚合物及复合材料的制备方法,以及共轭微孔聚合物在气体吸附和储存、污染物的富集、非均相催化、光发射、化学传感器、光捕集、电能存储等方面的应用。     

解凸约束非线性单调方程组的无导数谱PRP投影算法

本文在著名PRP共轭梯度算法的基础上研究了一种无导数谱PRP投影算法,并证明了算法在求解带有凸约束条件的非线性单调方程组问题的全局收敛性.由于无导数和储存量小的特性,它更适应于求解大规模非光滑的非线性单调方程组问题.数值试验表明,新算法对给定的测试问题是有效的和稳定的.     

一种新型共轭聚合物发光二极管老化的拉曼光谱研究

通过显微共焦拉曼光谱 ,对一种以新型的共轭聚合物半导体材料 3,4 (2 乙基己氧基 )苯基 1,3 丙二醇酯 (poly(2 (4 Ethylhexyl) phenyl 1,4 phenylenevinylene) (P PPV) )为发光层的聚合物发光二极管(PLEDs)器件进行了老化研究 ,无论是光致发光光谱还是拉曼光谱都提供证据说明造成器件老化的原因主要是发光层的聚合物的主链结构 ,即聚合物的共轭结构被破坏 ,这对提高以P PPV作为发光层的PLEDs器件的性能提出有用信息。     

Ring-closing metathesis as a tool for the efficient preparation of chiral spirocyclic ethers from homoallylic alcohols

The preparation of chiral spirocyclic ethers via allylic etherification/olefin metathesis of homoallylic alcohols is investigated. This reaction sequence transforms the enantiopure substrate alcohols, synthesized by a one-pot asymmetric rhodium-catalyzed conjugate addition/metal-mediated allylation procedure, into the desired spiro ethers with full conversions and in excellent isolated yields. The synthetic sequence provides an efficient means for a rapid construction of functionalized spiro ethers in a stereoselective manner.     

Organocatalytic conjugate addition of 1-bromonitroalkanes to α,β-unsaturated aldehydes: synthesis of nitrocyclopropanes

A variety of secondary amines were studied as the catalyst in the conjugate addition of 1-bromonitromethane to α,β-unsaturated aldehydes. Proline was identified as the best catalyst for this reaction. MeOH/AcONa system was found to provide much better yields than CHCl₃/Et₃N system reported before. Good yields of nitrocyclopropane products were obtained with a variety of β-aryl acroleins. Several substituted 1-bromonitromethanes were also examined in the reaction. Both 1-bromonitroethane and 1-phenyl-1-bromonitromethane gave the corresponding nitrocyclopropanes in good yields. The diastereoselectivity of the reaction was strongly affected by the steric hindrance of 1-bromonitroalkanes.