取代冠醚的异构体计数

采用图论方法对取代冠醚的构造、构型以及手性构型和非手性构型进行计数。为了便于计数，取代冠醚的构型、手性构型和非手性构型的计数采用平面模型，并利用Ｐｏｌｙａ计数定理求出其计数母函数，最后使用计算机计算，结果列表给出。     

取代环烷烃和环烷烃同系物的异构体的计数

本文采用置换群D'_n(n)和计数级数 1+x+x²求出取代环烷烃的构造异构体的计数母函数,改进了Balaban的方法。同时,求出了环烷烃同系物的构造异构体、构型、手性构型和非手性构型的计数母函数。     

激子手性方法用于多氧取代环己烯类化合物的研究

多氧取代环己烯是一类比较独特的天然产物,分子中多具有四个手性中心,立体化学多变,尽管用化学衍生物方法确定了部分化合物的绝对构型,但对已报道的化合物中仍有大部分未能确定其构型。在阐明分子相对构型的基础上,应用激子手性方法确定此类化合物的绝对构型,并利用Alchemy程序进行了分子动力学计算,对此类化合物的圆二色性规律进行了总结。     

激子手性方法用于多氧取代环己烯类化合物的研究

多氧取代环己烯是一类比较独特的天然产物,分子中多具有四个手性中心,立体化学多变,尽管用化学衍生物方法确定了部分化合物的绝对构型,但对已报道的化合物中仍有大部分未能确定其构型。在阐明分子相对构型的基础上,应用激子手性方法确定此类化合物的绝对构型,并利用Alchemy程序进行了分子动力学计算,对此类化合物的圆二色性规律进行了总结。     

新型手性膦配体的合成及其在 1,4-共轭加成反应中的应用

 以联萘酚和大位阻的金刚烷酰氯为原料, 经两步合成了系列新型手性单齿亚磷酸酯配体, 并应用于铜催化的二乙基锌对环烯酮的不对称 1,4-共轭加成反应. 结果表明, 产物收率和对映选择性最高分别为 95% 和 61%. 配体 (S)-(2-(adamantane- 1-carboxylic acid)-1,1’-binapthalen-2’-yl)-((S)-1,1’-binaphthalen-2,2’-yl)phosphite [(S,S)-3a]的两个 (S)-联萘酚构型是匹配的组合, 产物的绝对构型主要由配体中 2,2’-二氧膦-1,1’-联萘酚的构型控制.     

含金刚烷基团的新型手性单齿亚磷酸酯配体的合成及其在不对称1,4-共轭加成反应中的应用

以轴手性的BINOL/H8-BINOL(BINOL为联苯酚)和大位阻的金刚烷酰氯为原料,合成了系列新型手性单齿亚磷酸酯配体,并应用于Cu催化的二乙基锌对环烯酮的不对称1,4.共轭加成反应中.结果表明,配体结构中部分氢化的2,2'-(1,1'-联萘基)亚磷酸酯单元和金刚烷基团,有助于改善反应的对映选择性,对映选择性最高可...     

小议金刚烷

《化学教学》1998年第6期刊载的"金刚烷浅议"一文中曾指出金刚烷的二氯取代物有10种[1],《化学教学》1999年第5期刊载的"金刚烷分子的二氯代物有几种"一文曾对此提出异议,并指出金刚烷的二氯取代物只有6种[2].     

手性噁唑硼烷结构与还原苯基乙基甲酮的对映选择性研究~≠

本文以苯基乙基甲酮为还原底物,研究了原地(in situ)制备的在3、4、5位具有不同取代基的手性1,3,2-(口恶)唑硼烷催化剂的结构与不对称催化效应关系。研究结果表明,在不对称催化硼烷还原反应中(CBS方法),产物的构型和对映选择性主要受手性(口恶)唑硼烷的4位取代基控制。     

手性（恶）唑啉催化醛的不对称苯基转移反应

以3-羟基金刚烷羧酸和手性氨基醇为原料,合成了4个嘿唑啉金刚烷醇催化剂,并将其应用于醛的不对称苯基转移反应,得到了较好产率(62%～85%),e.e.值最高为54%.     

手性联二萘酚衍生物催化的苯乙炔与苯甲醛不对称加成反应

以手性联二萘酚为原料,合成了3,3′位取代的手性联二萘酚衍生物,研究了该衍生物配体在二乙基锌存在下,催化苯乙炔与苯甲醛的不对称加成反应,产物的产率为73%,e.e.值为40%。 研究结果表明,手性联二萘酚衍生物结构的微小变化导致催化产物构型的改变。     

13C nuclear magnetic resonance spectra—VII: Through-bond interactions and hyperconjugative substituent effects at 2,4-disubstituted adamantanes

The ¹³C NMR spectra of a series of 2,4-disubstituted adamantanes with the substituents in various configurations are reported and discussed in terms of through-bond and through-space interactions of the substituents. Through-bond interactions in equatorially disubstituted adamantanes and equatorially substituted adamantanones are attributed to overlapping of free-electron pairs and bond orbitals in symmetrically favoured orientations.     

Molecular size and shape properties of diamondoid molecules occurring in crude oil

The molecular size and shape for 27 diamondoids molecules (adamantanes and alkyladamantanes, diamantine and alkyldiamantanes) were calculated by computational quantum mechanical modeling method of dispersion correction B3LYP-D3/6-311+G**, in which the family of adamantanes presents molecular sizes in terms of width of 6.8–7.9 Å, and for the family of diamantanes 6.8–7.4 Å, in terms of length the size for adamantanes are 7.6–9.5 Å and for diamantanes 9.3–10.0 Å and in terms of height are rounded from 7.4 to 9.6 Å for adamantanes and 7.4 to 8.5 Å for diamantanes. This size depends on the alkyl substitution either in CH₂ or CH bridgehead positions. A measure of spherical shape deviation in terms of ovality, (O = 1 for sphere shape) was calculated, in which for adamantane, methyladamantanes, dimethyladamantanes, and multi-substituted adamantanes, is 1.17, 1.21, 1.24, and 1.26–1.31, respectively and ovality value for diamantane is 1.20 and 1.22–1.27 for methyl substituted diamantanes. Ovality (shape) and molecular size differences between adamantane, methyladamantanes, dimethyladamantanes, multi-substituted adamantanes, and the corresponding diamantanes allow suggesting a dynamic model for separation from the linear alkanes in a mixture into a slit pore shape typical for microporous carbons.     

Benchmarking thermochemical experiments and calculations of nitrogen-containing substituted adamantanes

Standard molar enthalpy of formation of 2-cyano-adamantane was obtained by using high-precision combustion calorimetry. The standard molar enthalpies of sublimation of 2-cyano-adamantane and 2,2-dinitro-adamantane at 298.15 K were derived from the vapor pressure temperature dependences measured by transpiration. The molar enthalpies of fusion of these compounds were measured with the help of differential scanning calorimetry. Thermochemical data on functional substituted adamantanes containing nitrogen in the substituents were collected and evaluated. The gas-phase enthalpies of formation were calculated with the high-level quantum-chemical method G4 and compared with the experimental results. The consistent data set of the benchmark quality was suggested for practical thermochemical calculations. Geminal destabilizing effects for the interactions of nitro- and cyano-substituents placed in the second position on the adamantane cage were derived. Structure–property correlations for substituted adamantanes and aliphatic substituted alkanes were found and suggested for the assessment of the gas-phase enthalpies of formation of adamantane derivatives.

     

Configurational assignment of several 1,4-substituted adamantanes

The configurations of several 1,4- (= 2,5-) disubstituted adamantanes have been determined by means of X-ray diffraction. Since these compounds have rigid skeletons and since there is almost no difference in stability or steric requirements between the geometric isomers, these epimers are expected to be very useful for stereochemical studies.     

Synthesis of (3-Hydroxyadamantan-1-yl)methanols

A convenient procedure has been developed for the synthesis of (3-hydroxyadamantan-1-yl)-methanols on the basis of nitroxylation of adamantan-1-ylmethanols with fuming nitring acid and subsequent reduction of intermediate nitric acid esters with hydrazine hydrate. The title diols have also been obtained by the reduction of 1-nitroxy-3-(nitroxymethyl)adamantanes. The nitroxylation process is accompanied by oxidation with the formation of substituted adamantane-1-carboxylic acids.     

Adamantanes as spherical nanosondes in adducts with a chiral dirhodium complex-discriminating enantiomers and probing spatial proximities

Three different kinds of substituted chiral adamantane molecules—adamantanones, dioxolanoadamantanes and dithiolano—adamantanes—were studied in the dirhodium experiment (NMR measurement with 1:1 molar mixtures with Rh^(II)₂[(R)‐(+)‐MTPA]₄ in CDCl₃). Their different behavior in adduct formation is described, and the possibility of determining enantiomeric purities and absolute configurations is explored. Detailed inspection of one‐ and two‐dimensional NMR experiments allowed for an interpretation of steric and electronic intra‐adduct interaction showing that the phenyl groups of Rh* tend to enwrap the bound adamantane ligand so that through‐space effects over a range of 6–7 Å away from the binding rhodium atom can be observed. Even slight differences in the relative orientation of phenyl groups can be monitored when comparing diastereomeric adducts via NMR signal dispersion. Copyright © 2011 John Wiley & Sons, Ltd.     

Semipinacol and protoadamantane-adamantane rearrangements of 5,6-dibromoadamantan-2-one and -2-ol

A number of new polybrominated adamantanes were formed by rearrangements and bromination of 2,2,6,6-tetrabromoadamantane under Friedel-Crafts conditions. Protoadamantane-4,10-dione, 10-acetoxyprotoadamantan-4-one, 1,2,6-triacetoxyadamantane and 5,6-diacetoxyadamantan-2-one were formed by successive semipinacol and protoadamantane-adamantane rearrangements of 5,6-dibromoadamantan-2-one and 5,6-dibromoadamantan-2-ol. This work may open up new pathways for the synthesis of 1,2,6-trisubstituted adamantanes.     

Selective fluorination of adamantanes by an electrochemical method

Selective fluorination of adamantanes was achieved by the electrochemical fluorination method, using Et 3N-5HF as electrolyte and a fluorine source. Mono-, di-, tri-, and tetrafluoroadamantanes were selectively prepared from adamantanes by controlling the oxidation potential, and the fluorine atoms were introduced selectively at the tertiary carbons. Adamantanes that have functional groups such as ester, cyano, and acetoxymethyl were also fluorinated selectively.     

13C NMR spectra of adamantane derivatives

The carbon-13 chemical shifts of mono- and 1,3-disubstituted adamantanes are reported. The effects caused by the substituents are compared with those met in aliphatic and alicyclic compounds. It is shown that the 1,4-interactions have only minor importance in l-substituted adamantanes. The influence of polar groups on the chemical shifts of γ- and δ-carbon atoms is a typical ‘through-the-bonds’ interaction and correlates with inductive parameters of the substituents.