Aromatische Spirane, 21. Mitt: Darstellung von Methylphthalaldehydsäuren und ihren Ethylund Methylestern als Synthone für Synthesen von methylierten 2,2′-Spirobiindandionen

Summary The isomeric methyl phthalaldehydic acids11 were obtained from phthalides4 by bromation (NBS) to the 3-bromo derivatives7 and subsequent hydrolysis with water.4 in turn were accessible from dimethyl methyl benzoates1 by dibromination withNBS and subsequent thermical cyclization to the bromo derivatives3 which, on catalytic dehalogenation, afforded the phthalides4. Reaction of11 with methanol or ethanol gave the pseudo-esters13 and14, resp. Short treatment of11 with diazomethane on the other hand yielded the methyl formyl benzoates15b to15e. Prolonged reaction (several hours) gave the oxiranyl compounds17; in addition, the acetonyl derivatives18 were also found, obviously formed by a double methylene insertion into15. All reactions proceeded with good to excellent yields.

     

Regio- and diastereo-controlled synthesis of bis(formylmethano)[60]fullerenes and their application to the formation of [60]fullerene pearl-necklace polyimines

The tether-directed method was firstly applied to the biscyclopropanation of [60]fullerene via the addition-elimination reaction of bis(sulfonium ylide)s to give bis(formylmethano)[60]fullerenes with satisfactory regio- and stereoselectivity. The equatorial-bisadduct thus obtained was used for the polycondensation with an aromatic diamine to afford the corresponding pearl-necklace polyimine with satisfactorily high degree of polymerization.     

Palladium-catalyzed intramolecular α-arylation of aliphatic ketone, formyl, and nitro groups

Intramolecular arylation of properly designed substrates bearing a ketone, formyl, or nitro terminating group was achieved by use of a PdCl₂(Ph₃P)₂-Cs₂CO₃ reaction system to form a variety of carbocyclic compounds. Arylation in ketone compounds afforded benzene-annulated bridged or spirocycloalkanone derivatives, depending on the structure of the cyclization precursors. Arylation in formyl compounds occurred at the α-position (α-arylation) or at the carbonyl carbon (carbonyl-arylation) depending on the structure of the cyclization precursors and on the reaction solvent. An α-arylated secondary nitro group was partially transformed to ketone in the manner of the Nef reaction, whereas a tertiary nitro group was partially eliminated to afford a styrene-type olefin.     

Synthesis and applications of (5-substituted benzimidazolo)-benzo-15-crown-5 and 4,4′-bis-benzimidazolo-dibenzo-15-crown-5 for the colorimetric detection of Au3+

In the present work, we have reported the synthesis of benzimidazoles functionalized crown ether derivatives of 4-formyl benzo-15-crown-5/4,4′-diformyl dibenzo-15-crown-5 and substituted diamine pyridine using sulfamic acid as a catalyst in DMSO. These molecules are used for the colorimetric determination of Au³⁺ selectively among other metal cations such as Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, Au³⁺ and Ag⁺ ions_.     

New Developments in Superacid Chemistry: Characterization of HC+=O and FC+=O Cations

A high gas pressure and use of the superacid HF/SbF₅ (1/1) were required for direct spectroscopic characterization of the HC⁺=O cation, which was until recently discussed as the short-lived intermediate of carbonylation reactions. The fluorocarbonyl cation FC⁺=O, which was equally difficult to characterize, was also directly observed with NMR spectroscopy as the product of protolytic cleavage of tert-butyl fluoroformate [Eq. (a)].     

HCO+和HOC+与C2H2气相质子转移反应的理论研究

在 HF,B3LYP和 QCISD(T)水平上研究了 HCO+和 HOC+与 C2 H2 的气相质子转移反应 .结果表明 :高级电子相关效应对研究质子转移过程极为重要 ;HCO+和 HOC+通过质子垂直进攻 C2 H2 的 π-键分别生成中间体 OC· HC2 H+2 和 CO· HC2 H+2 ,最终生成主要产物为π-质子化的乙炔 HC(H) CH+;对于质子转移反应 HOC+比 HCO+更为活泼 .计算结果与实验结果符合得较好 ,这将有助于理解星际化学以及燃烧化学中的质子转移过程     

CI AM1 study of the electronic structure of isomeric formyl benzonaphthyridines

For six isomeric formyl derivatives of 1,5-, 1,6- and 4,6-benzonaphthyridines the electronic structure and UV spectral values have been calculated by CI AM1 method. Correlations of the calculated and observed wave number values of considered compounds show good compatibility.     

HNCO+HCO→NCO+CH2O氢转移反应的从头算及动力学研究

在UMP2 (Full) /6 311G(d ,p)计算水平上 ,优化了标题反应的反应物、过渡态、产物的几何结构 ,沿最小能量途径讨论了异氰酸 (HNCO)和甲酰自由基 (HCO)发生氢转移反应位能面上驻点的结构以及相互作用分子结构变化 .指出该反应是一个N -H键断裂和C -H键生成的协同反应 .进一步采用UQCISD(T ,Full)方法对反应途径上的驻点进行了单点能量校正 ,得出该反应的计算位垒是 91.4 7kJ/mol,与实验值 10 8.92kJ/mol接近 .在5 0 0～ 2 5 0 0K实验温度范围内 ,运用变分过渡态理论 (CVT)计算得到的速率常数与实验观测值进行了比较 .     

Formyl phloroglucinol meroterpenoids from Eucalyptus tereticornis and their bioactivities

Five new formyl phloroglucinol meroterpenoids (FPMs), eucalteretials A?E (1–5), along with eight known analogues (6?13), were isolated from the twigs and leaves of Eucalyptus tereticornis. Their structures were established mainly by analysis of comprehensive spectroscopic data, and their absolute configurations were determined by electron circular dichroism (ECD) calculation. Within FPMs, both 1 and 2 are rare adducts of formyl phloroglucinol moiety and germacrene unit with different coupling patterns, respectively. Compound 3 exhibited significant cytotoxicity against HCT116?cell line with an IC₅₀ value of 4.76?μM. In addition, 5 and 9 were proved to be rare topoisomerase I (Top1) inhibitors.     

An ab initio study of the A Ac1 hydrolysis mechanism of formamide

Ab initio calculations have been used to examine the reaction profile for the A _wc1 hydrolysis mechanism for formamide, giving a value of 67.3 kcal/mole for H . Comparisons between computed and experimental proton affinities are used to assess the reliability of the calculations. Orbital energies are reported for formamide, N-protonated and O-protonated formamide, carbon monoxide and the formyl cation.