Double-tandem [4π+2π]·[2π+2π]·[4π+2π]·[2π+2π] synthetic sequence with photoprotolytic oxametathesis and photoepoxidation in the chromone series

Chromones are introduced into a double-tandem [4(π)+2(π)]·[2(π)+2(π)]·[4(π)+2(π)]·[2(π)+2(π)] synthetic sequence, culminating in photoprotolytic oxametathesis, which leads to an expeditious growth of molecular complexity over a few experimentally simple steps. The overall reaction can potentially be utilized in diversity-oriented synthesis, as it allows for three or more diversity inputs furnishing novel unique polycyclic scaffolds decorated with a variety of functionalities and aromatic/heterocyclic pendants. The polycyclic alkenes, resulting from the oxametathesis step, were found to undergo efficient and clean photoinduced epoxidation when irradiated in the presence of molecular oxygen.     

Microwave-Accelerated Ruthenium-Catalyzed [2π + 2π] Cycloadditions of Dimethylacetylene Dicarboxylate with Norbornenes

An efficient and convenient procedure has been developed for the ruthenium-catalyzed [2π + 2π] cycloadditions of dimethylacetylene dicarboxylate with norbornenes. Reaction is significantly accelerated in microwave conditions, while the commonly used benzene solvent was replaced by environmentally benign tetrahydrofuran.

π电子总能量E_π与走步数S_(2l)的关系

本文推导并分析了几类共轭烃的闭走步数公式及其内在联系,得到了HMO E_n展开系数应满足的一些条件,提出了一种估算E_n的新方法。     

Ph(SiMe_2)_nPh体系π→π~*UV谱的研究

本文依据Spin-Free理论,使用Gelfand基构造多电子波函数,采用四轨道模型,对Ph(SiMe_2)_nPh体系(n=1～6)的π→π*跃迁进行了EHMO-CI计算,所得第一及第二跃迁能与UV谱的实验结果基本一致。当体系硅链原子数增加时,第一吸收带红移的现象起因于LUMO中d轨道成份增加,导致电子排斥作用变化。在LUMO中,硅链上的d轨道以πd的形式与苯环π~*轨道进行πd—π~*共轭互相作用,这种作用很可能与第一吸收带的强度有内在的联系。     

CH2F2…H2O中强π型二级氢键

通过从头计算,用较大基组６－３１１＋Ｇ(２ｄ,２ｐ),在ＭＰ２水平上计算得到ＣＨ２Ｆ２…Ｈ２Ｏ体系的优化几何构型,与实验结构一致．其中∠Ｆ…Ｈ－Ｏ＝１１６．５°,偏离普通氢键之键角达到６３．５°．为探讨产生氢键巨大弯曲的原因,采用点电荷扫描的办法,探测ＣＨ２Ｆ２…Ｈ２Ｏ体系中Ｈ２Ｏ的Ｏ原子上的两对孤电子对的方向,发现了一个强的π型二级氢键相互作用．使用这种新的相互作用方式说明了产生这一巨大氢键弯曲的原因,并且在ＭＰ４水平上使用Ｃｏｕｎｔｅｒｐｏｉｓｅ技术计算了π型二级氢键的稳定化能．     

±π/2型相角的代数估算方法

本文以p212121空间群为例, 采用结构因子代数方法推导出适用于±π/2型相角估算的1.5阶和2.5阶代数公式, 并应用于两个已知晶体结构的±π/2相角计算, 获得了令人满意的结果。     

Regioselective [6π+2π] cycloaddition of 1,2-dienes to 7-substituted 1,3,5-cycloheptatrienes catalyzed by Ti(acac)2Cl2—Et2AlCl

A reaction of 7-alkyl-, 7-allyl-, 7-phenyl-1,3,5-cycloheptatrienes with 1,2-dienes in the presence of the two-component catalytic system Ti(acac)₂Cl₂—Et₂AlCl, which led to the formation of practically important substituted endo-bicyclo[4.2.1]nona-2,4-dienes in up to 90% yields, was accomplished for the first time.     

层叠苯环π-π相互作用的理论研究

利用DFT B3LYP/3-21G方法,对多个平行重叠排列的苯环体系进行研究.计算结果发现,平行苯环对称中心的距离(d)在0.40～0.46nm之间时,苯环以倾斜的方式层叠,即平行移位结购排列,体系能量有最小值,苯环平面的法线与各苯环中心连线的夹角(A)根据距离的不同分别为:d=0.40nm,A=25°;d=0.42nm,A=29°;d=0.44nm,A=34°d=0.46nm,A=40°.此结果与聚苯乙烯STM图像中苯环的排列结构十分吻合,测得值:d=0.43nm,A=25～30°.     

Ti-catalyzed [6π + 2π] cycloadditions of allenes with 1,3,5-cycloheptatriene

The reaction between 1,2-dienes and 1,3,5-cycloheptatriene in the presence of the two-component catalyst, TiCl₄-Et₂AlCl leads to the regioselective formation of endo-bicyclo[4.2.1]nona-2,4-diene derivatives in yields of up to 80%.     

芳环超分子体系中的π-π作用

π-π作用是芳环超分子体系中广泛存在的一种重要的弱相互作用. 本文对π-π作用的特征、形式、有效参数和表征方法等作了比较全面的综述, 同时小结了影响π-π作用的一些重要因素, 最后还概述了近年来π-π作用在超分子组装、不对称催化、有机半导体材料等领域的研究进展.     

Donor-(π-bridge)-azinium as D-π-A+ one-dimensional and D-π-A(+)-π-D multidimensional V-shaped chromophores

Heteroaromatic cations reacted with N-heteroarylacetylenes under Sonogashira conditions to allow easy access to potential single donor D-π-A(+) and V-shaped D-π-A(+)-π-D chromophores, where the acceptor moiety A is the π-deficient pyridinium cation and the donor moiety is represented by different π-excessive N-heterocycles. The β hyperpolarizabilities were measured using hyper-Rayleigh scattering experiments and the experimental data are supported by a theoretical analysis that combines a variety of computational procedures, including Density Functional Theory (DFT) and correlated Hartree-Fock-based methods (RCIS(D)).     

Cobalt(I)-catalyzed [4π+2π] cycloaddition reactions of 1,3-diynes with 1,3,5-cyclooctatriene

The cycloaddition reaction between conjugated diynes and 1,3,5-cyclooctatriene in the presence of the catalyst Co(acac)₂/dppe/Zn/ZnI₂, led to the selective formation of tricyclo[4.2.2.0^2,5]deca-7,9-diene derivatives in 72–85% yield.     

OCS,CO2,N2O与烯、炔烃之间π…π作用的电子密度拓扑研究

采用MP2/aug-cc-pVDZ方法对氧硫化碳(OCS)、二氧化碳(CO2)、一氧化二氮(N2O)与乙烯(C2H4)、乙炔(C2H2)、2-丁炔(C4H6)之间形成的平行构型复合物中的分子间相互作用进行了理论研究.复合物的相互作用能按照B…C2H4B…C2H2>B…C4H6(B=OCS,CO2,N2O)的顺序依次减小.采用电子密度拓扑分析理论方法,讨论了复合物中π…π作用的成键特性.电子密度拓扑分析表明复合物中形成了弱的分子间相互作用,且以静电作用为主;π电子密度分子图与全电子密度分子图中键径方向是一致的,说明π…π作用在本文所讨论的体系中起着很重要的作用.NBO分析表明净电荷迁移从电子给体C2H4,C2H2,C4H6到电子受体OCS,CO2,N2O,迁移数按照B…C2H4相似文献   

基于π-π相互作用合成星型聚丙烯腈-石墨烯复合材料

首先合成含有6个羟基的三亚苯衍生物,然后通过氧化还原引发体系合成了星型聚丙烯腈聚合物(SPAN),最后在星型聚丙烯腈的N,N-二甲基甲酰胺溶液(DMF)中用水合肼还原氧化石墨得到均一稳定的溶液。分别通过红外光谱(FT-IR)、核磁共振谱(1H-NMR)、凝胶渗透色谱(GPC)、扫描电镜(SEM)等对产物进行表征。结果表明,星型聚丙烯腈成功吸附到石墨烯表面。     

π-Expanded Borazine: An Ambipolar Conjugated B-π-N Macrocycle

Staying at a B 'N' B: A highly symmetric cyclic structure in which N donor and B acceptor sites are alternating is found for the first ambipolar π-conjugated B-N macrocycle. The donor-π-acceptor arrangement results in mutual interactions between B and N and a pronounced solvatochromic effect on the emission. The strong luminescence in solution also lends itself to use in anion recognition.     

First example of [6π+2π] cycloaddition of 1,2-dienes to 1,3,5,7-cyclooctatetraene catalyzed by CoI compounds

A stereoselective [6π+2π] cycloaddition of 1,2-dienes to 1,3,5,7-cyclooctatetraene in the presence of a multi-component catalytic system CoI₂/dppe/Zn/ZnI₂, which led to the formation of substituted (E)-bicyclo[4.2.2]deca-2,4,7-trienes in 76—87% yields, was accomplished for the first time.     

Titanium-catalyzed [6π+2π]-cycloaddition of Si-containing alkynes to bis(1,3,5-cycloheptatriene-7-yl)alkanes

The reaction between Si-containing alkynes and bis(1,3,5-cycloheptatriene-7-yl)alkanes in the presence of the two-component catalyst Ti(acac)₂Cl₂-Et₂AlCl, led to the selective formation of mono- and bis-adducts – {9-[4-(2,4,6-cycloheptatrienyl)alkyl]-8-alkyl(phenyl)bicyclo[4.2.1]nona-2,4,7-triene-7-yl}(trimethyl)silanes and bis(7-trimethylsilyl-8-alkyl(phenyl)bicyclo[4.2.1]nona-2,4,7-triene-7-yl)alkanes in 78–86% yield. The structures of the obtained cycloadducts were confirmed by ¹H and ¹³C NMR spectroscopy.     

1,3- versus 1,4-[π4+π2] Cycloadditions between methyl glyoxylate oxime and cyclopentadiene or cyclopentene

The acid catalyzed cycloaddition reaction of methyl glyoxylate oxime with cyclopentadiene (CPD) afforded the corresponding aza-Diels–Alder adducts, the endo and exo isomers of (±)-methyl 2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylates, and as the major product a 1,3-cycloadduct, methyl (1RS,4RS,5RS)-(2-oxa-3-azabicyclo[3.3.0]oct-7-ene)-4-carboxylate. The similar reaction using cyclopentene (CP) provided only the 1,3-cycloadduct methyl (1SR,4RS,5SR)-(2-oxa-3-azabicyclo[3.3.0]octane)-4-carboxylate. The influence of various parameters on the reaction outcome was studied and, based on the results obtained, a mechanism for the formation of both 1,3- and 1,4-cycloadducts is proposed. The structure of all adducts was confirmed by NMR spectroscopic data and/or by X-ray crystallography.     

确定分子中离域π键πnm的方法

A method for obtaining the delocalized π bonds π_n^m in a molecule has been discussed in this paper, and the delocalized π bonds π_n^m in linear, bent, planar trigonal, single cyclic conjugated, and polycyclic conjugated molecules have been studied. The reasons of π₃⁴ in NO₂ and 2π₃² in C₃ molecules have been proposed. The delocalized π bonds 2π₁₈¹⁸ in cyclo[18] carbon are analyzed.     

Synthesis of 1,3-Dioxan-2-ones by Photo-Aerobic Selenium-π-Acid Multicatalysis

An expedient method for the synthesis of cyclic carbonates from homoallylic carbonic acid esters by means of photo-aerobic selenium-π-acid multicatalysis is reported. Until now, conceptually related methods commonly relied either on the stoichiometric addition of electrophiles onto the substrate's alkene moiety or the presence of pre-installed leaving groups in allylic position of said alkene to – in part, catalytically – initiate an intramolecular attack by an adjacent carbonic acid ester group. In sharp contrast, the current study shows that the C−C double bond of homoallylic carbonic acid esters can be directly activated by the catalytic interplay of a pyrylium dye and a diselane using ambient air as the sole oxidant and visible light as an energy source.