Hydrogenation of a double bond in a side chain of dibenzene chromium

Russian Chemical Bulletin -     

Aldehydes of furan series in the synthesis of 1,7-phenanthroline derivatives

By condensation of quinolin-5-amine with 5-arylfuran-2-carbaldehydes and cyclohexane-1,3-dione or dimedone new compounds were synthesized, 10,10-dimethyl-7-(5-arylfuran-2-yl)-9,10,11,12-tetrahydrobenzo[b][1,7]phenanthrolin-8(7H)-ones unsubstituted in the position 10.     

Ion chemistry of anti-o,o dibenzene

The ion chemistry of anti-o,o'-dibenzene (1) was examined in the gaseous and the condensed phase. From a series of comparative ion cyclotron resonance (ICR) mass spectrometry experiments which involved the interaction of Cu+ with 1, benzene, or mixtures of both, it was demonstrated that 1 can be brought into the gas phase as an intact molecule under the experimental conditions employed. The molecular ions, formally 1*+ and 1*- , were investigated with a four-sector mass spectrometer in metastable-ion decay, collisional activation, charge reversal, and neutralization-reionization experiments. Surprisingly, the expected retrocyclization to yield two benzene molecules was not dominant for the long-lived molecular ions; however, other fragmentations, such as methyl and hydrogen losses, prevailed. In contrast, matrix ionization of 1 in freon (77 K) by gamma-radiation or in argon (12 K) by X-irradiation leads to quantitative retrocyclization to the cationic dimer of benzene, 2*+. Theoretical modeling of the potential-energy surface for the retrocyclization shows that only a small, if any, activation barrier is to be expected for this process. In another series of experiments, metal complexes of 1 were investigated. 1/Cr+ was formed in the ion source and examined by metastable ion decay and collisional activation experiments, which revealed predominant losses of neutral benzene. Nevertheless, comparison with the bis-ligated [(C6H6)2Cr]+ complex provided evidence for the existence of an intact 1/Cr+ under these experimental conditions. No evidence for the existence of 1/Fe+ was obtained, which suggests that iron mediates the rapid retrocyclization of 1/Fe+ into the bis-ligated benzene complex [(C6H6)2Fe]+.     

Synthesis of substituted nitriles of dibenzenechromium series using chromium vapors

Conclusions Some mixed bisarenechromium complexes, namely toluene (benzonitrile) chromium, anisole (benzonitrile) chromium, and acetophenone (benzonitrile) chromium were obtained by the reaction of Cr with two aromatic compounds in the vapor phase.Translated from Izvestiya Akademli Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 420–422, February, 1984.The authors thank N. I. Vasyukova and A. G. Makarovskaya for making the mass spectrometric and GLC studies.     

Vibrational spectroscopy and density functional theory of transition-metal ion-benzene and dibenzene complexes in the gas phase

Metal-benzene complexes of the form M(benzene)(n) (M = Ti, V, Fe, Co, Ni) are produced in the gas-phase environment of a molecular beam by laser vaporization in a pulsed nozzle cluster source. These complexes are photoionized with an ArF excimer laser, producing the corresponding cations. The respective mono- and dibenzene complex ions are isolated in an ion-trap mass spectrometer and studied with infrared resonance enhanced multiple-photon dissociation (IR-REMPD) spectroscopy using a tunable free electron laser. Photodissociation of all complexes occurs by the elimination of intact neutral benzene molecules, and this process is enhanced on resonances in the vibrational spectrum, making it possible to measure vibrational spectroscopy for size-selected complexes. Vibrational bands in the 600-1700 cm(-1) region are characteristic of the benzene molecular moiety with systematic shifts caused by the metal bonding. The spectra in this solvent-free environment exhibit periodic trends in band shifts and intensities relative to the free benzene molecule that varies with the metal. Density functional theory calculations are employed to investigate the structures, energetics, and vibrational frequencies of these complexes. The comparison between experiment and theory provides fascinating new insight into the bonding in these prototypical organometallic complexes.     

tBuOLi-Mediated Alkynylation of Aldehydes

The lithium tert-butoxide reagent was found to promote the addition of terminal aromatic alkynes to various aromatic aldehydes. This reaction was efficiently carried out in anhydrous dimethylformamide at room temperature in air for 50 min, and the corresponding propargylic alcohols were obtained in good to excellent yields (up to 95%).

Studies on the Hydrosilation of Aromatic Aldehydes

The dependence of reactivity on molecular structure in hydro-silation of aromatic aldehydes catalyzed by (PPh3)3 RhCl was studied by “IN SITU” FT-IR technique and a plausible mechanism was proposed.The results show that: (1) Model reaction Ⅰ, Ⅱ and Ⅲ are all characterized by an induction period; (2) The reaction constant of model reaction Ⅰ is +1.57, so the rare of reaction Ⅰ is increased by the electron-withdrawing groups; (3) The rate of model reaction Ⅲ decreases when the size of R1 becomes larger; (4) The reaction constant of model reaction Ⅲ is -0. 50, so the rate of it is increased by electron-donating groups.     

Beryllium-Induced Conversion of Aldehydes

Aldehydes play a key role in the human metabolism. Therefore, it is essential to know their reactivity with beryllium compounds in order to assess its effects in the body. The reactivity of simple aldehydes towards beryllium halides (F, Cl, Br, I) was studied through solution and solid-state techniques and revealed distinctively different reactivities of the beryllium halides, with BeF₂ being the least and BeI₂ the most reactive. Rearrangement and aldol condensation reactions were observed and monitored by in situ NMR spectroscopy. Crystal structures of various compounds obtained by Be²⁺-catalyzed cyclization, rearrangement, and aldol addition reactions or ligation of beryllium halides have been determined, including unprecedented one-dimensional BeCl₂ chains and the first structurally characterized example of an 1-iodo-alkoxide. Long-term studies showed that only aldehydes without a β-H can form stable beryllium complexes, whereas other aldehydes are oligo- and polymerized or decomposed by beryllium halides.     

Synthesis of Difluoromethylthioesters from Aldehydes

Difluoromethylthioester compounds are yet another important kind of organofluorine compound and are reported here for the first time. They can be efficiently synthesized from various aldehydes. The synthetic method features mild reaction conditions, good tolerance of functional groups, broad substrate scope, and importantly, no metal is involved in the reaction. The approach has the potential to become an important tool for the late‐stage functionalization of advanced synthetic intermediates, and should have many applications in medicinal chemistry.     

醛类自氧化振荡反应动力学的研究

研究了醛类在乙酸和水混合溶剂中以Ｃｏ＾２＋和Ｂｒ＾－为催化剂的自氧化振荡反应。得知某些取代苯甲醛和脂肪醛在适当条件下能发生振荡，并研究了苯甲醛、正丁醛和乙醛的周期受动力学制约的影响，提出了相关的机理模型。依此模型以Ｇｅａｒ方法计算其振荡周期基本与实验结果相符。     

Heat capacity of molecular chromium sandwich compounds: chromocene Cr(C5H5)2 and dibenzene chromium Cr(C6H6)2

Heat-capacity measurements have been made in the temperature range 110 to 300 K. In the range 160 to 240 K the chromocene curve shows an anomaly related to an order-disorder phase transition in the solid. On the other hand the dibenzene chromium curve indicates no phase transition and is in accordance with an ordered structure at room temperature.     

Reaction of Hexamethyldisilazane with Aldehydes

Russian Journal of General Chemistry -     

Magnetochemical properties of tetranuclear rhodoso and Pfeiffer chromium(III) complexes in a series of compounds

Seven salts of the structurally related tetranuclear rhodoso and Pfeiffer chromium(III) complexes were prepared. Magnetic susceptibilities were measured and the energy splittings of the electronic ground state caused by exchange interactions were determined. There are marked differences in the low-temperature magnetic properties. Crystal packing and hydrogen bonding effects are the most likely causes for the differences in the exchange-splitting pattern.     

Iridium-Catalyzed Formyl-Selective Deuteration of Aldehydes

We report the first direct catalytic method for formyl-selective deuterium labeling of aromatic aldehydes under mild conditions, using an iridium-based catalyst designed to favor formyl over aromatic C−H activation. A good range of aromatic aldehydes is selectively labeled, and a one-pot labeling/olefination method is also described. Computational studies support kinetic product control over competing aromatic labeling and decarbonylation pathways.     

醛的不对称烯丙基化反应研究进展

醛的不对称烯丙基化反应是合成手性烯丙基醇的一类重要方法, 从手性辅基控制反应和化学催化不对称反应两个方面对近20多年来的相关报道进行综述.