Solvent effect on regioselectivity of epoxide ring opening in styrene oxide by O- and N-nucleophiles in neutral and basic media

The results of ring opening in styrene oxide by alcohols, amines, amino alcohols, and diamines were generalized. On low polarizing ability of the solvent, the main direction of the process is the formation of normal α-substituted products. The solvent effect on regioselectivity of the reaction was studied for N,N-diethylethylenediamine. The ratio of products correlates well with the value of dielectric constant for mixed aqueous-organic solvents and with the parameters of polarity E _T and AN for neat solvents.     

Main stages of unusual allyl coupling involving nickel bis-η3-allyl complexes in the presence of dichlorobutenes

The reactions of nickel bis-η³-allyl complexes with dichlorobutenes were studied. The overall process includes several stages, each characterized by substantially different reactions: traditional allyl coupling, substrate insertion between recombining allyl ligands, and the trimerization of allyl fragments accompanied by hydride transfer (unusual allyl coupling). Unusual allyl coupling occurs at a final stage preceded by the formation of oligomeric nickel intermediates with the mean composition Ni₄(C₃H₅)₆(C₄H₆)₃Cl₇. Their decomposition gives nonadiene and nonatriene isomers and propene. Trace amounts of molecular hydrogen were found indicating the formation of nickel hydride complexes at the final stage. Nickel bis-η³-allyl complexes react similarly with different dichlorobutenes.     

Catalytic syntheses of polycyclic compounds based on norbornadiene in the presence of nickel catalysts

The cycloadditions of olefins containing an electron-withdrawing substituent to norbornadiene are reported. The influence of the substituent and solvent nature on the [2+2+2]-cycloadduct yield and stereoselectivity is elucidated. The competitive cycloaddition of pairs of olefins to norbornadiene is discussed. Hypotheses about the structure of key intermediates of the process are considered. The consistent generalized mechanism for the cycloaddition of unsaturated compounds of various classes to norbornadiene is suggested.     

Allylation of norbornadiene in the presence of Pd0 phosphine complexes: a DFT modeling

Russian Chemical Bulletin - The formation of products of oxidative and reductive allylation of norbornadiene by allyl formate (AF) in the presence of Pd0 triphenylphosphine complexes was modeled by...     

Paramagnetic complexes of nickel(I) stabilized by norbornadiene

Nickel(I) compounds whose concentration was 10^–4–10^–6 of the total concentration of nickel added to the system were identified by EPR in the reaction of 2,5-norbornadiene with nickel homoligand allyl complexes Niall₂ (all is C₃H₅, 1-CH₃C₃H₄, or 2-CH₃C₃H₄). The Ni(I) complexes were stable at room temperature under oxygen-free conditions. It was shown that the paramagnetic complexes were in equilibrium with diamagnetic forms. The temperature dependence of the concentration of the paramagnetic species was determined. The structure of the paramagnetic nickel(I) complexes and the possible routes of their formation are discussed on the basis of the obtained data.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 490–493, July–August, 1990.     

New Trends in the Development of Methods for Catalyst Preparation for the Processes of Organochlorine Synthesis

The formation of heterogeneous mercury-, zinc-, and copper-containing catalytic systems obtained by supporting salt components (SCs) without a solvent is studied. It is shown that due to strong interaction between SC and support, the size of salt clusters on the surface and their relative contribution decrease. That is, the concentration of excess salt phases decreases. The dispersity increases up to molecular distribution. When surface-linked two-dimensional disordered structures are formed, the state of salt phases in the compositions of catalytic systems changes. The surface mobility of salt clusters during the contact with the reaction medium is found. Compared to the systems obtained by impregnation with aqueous solutions, the proposed systems are 2–3 times more thermally stable, their surface is enriched in defect structures that are active in catalysis, and the processes of organochlorine synthesis become more efficient.     

Correlations between 13C NMR chemical shifts of [(1-R-η3-C3H4)PdCl]2 and Na[(1-R-η3-C3H4)PdCl2] and substituent constants

Linear correlations between ¹³C NMR chemical shifts of unsubstituted terminal carbon atom of the allylic ligand in [(1-R-η³-C₃H₄)PdCl]₂ and Na[(1-R-η³-C₃H₄)PdCl₂] and the modified Hammett constants were established. Two-parameter correlations using the Swain-Lupton parameters R ⁺, R ⁻, and F were obtained. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1171–1174, June, 2008.     

Algorithm and criterion of quality for assessing the packing of polymer microspheres

An algorithm for assessing the quality of the packing of two-dimensional ordered structures, prepared using polymer microspheres 20 μm in diameter on a water surface, is proposed. An analysis is performed on the basis of optical microscopy images. The area of the largest ordered microsphere domain in an image is used as the quality criterion. The algorithm simplifies analysis of the ordered structures.     

Specific Features of the Catalytic Hydrogenation of the Norbornadiene-Based Carbocyclic Compounds

Russian Journal of Coordination Chemistry - The gas- and liquid-phase hydrogenation of bicyclo[2.2.1]hepta-2,5-diene (norbornadiene) in the presence of the Pd/γ-Al2O3 (PK-25) industrial...