Progress in the synthesis and transformations of alkylidenecyclopropanes and alkylidenecyclobutanes.

Norbornene, norbornadiene and their derivatives: promising semi-products for organic synthesis and production of polymeric materials

Schleyer's discovery of hyperconjugative aromaticity and antiaromaticity in 5-substituted cyclopentadienes further expanded our understanding of the pervasive influence of aromaticity. Acceptors induce antiaromatic character by Schleyer's negative hyperconjugative aromaticity, and donors have the opposite effect. We computationally explored the Diels-Alder reactivity of 5-substituted cyclopentadienes with ethylene and maleic anhydride. The predicted billionfold difference in the computed gas phase rate constants at room temperature for the Diels-Alder reactions of 5-substituted cyclopentadienes with ethylene or maleic anhydride results from differences in the transition state distortion energies, which are directly related to the hyperconjugative aromaticity of these molecules.

Schleyer hyperconjugative aromaticity and Diels–Alder reactivity of 5‐substituted cyclopentadienes

Nanoporous PBI membranes by track etching for high temperature PEMs

Diels-Alder reactions of neat reactive dienes and dienophiles are frequently vigorous and have a limited preparative value. It is possible to control the temperature of multi-gram scale Diels-Alder reactions by adding a minimal amount of water to neat reactants. In addition, the presence of water resulted in an increased reaction rate and formation of a higher purity product. The use of minimal amounts of other solvents, with lower heat capacities, did not give good results. Furthermore, some dienophiles, e.g. maleic anhydride, reacted poorly in a dilute water suspension or solution, but worked well in the presence of a minimal amount of water. This is an environmentally friendly, practical and efficient approach to preparation of Diels-Alder adducts on a multi-gram scale.

https://www.tandfonline.com/doi/pdf/10.1080/17518250802482505

Diels-Alder reactions in the presence of a minimal amount of water

Norbornadiene (NBD) reacts with allyl esters All—OC(O)R (R = Me, But, Ph, CCl3, CF3) in acetonitrile solutions of palladium(0) complexes to give a mixture of four isomeric nontraditional allylation products and the corresponding carboxylic acids. Under similar conditions, the reaction of NBD with allyl formate in solutions of Pd0 and PdII complexes occurs selectively, resulting in the product of addition of the allyl fragment and the H atom to an NBD double bond, 5-allylbicyclo[2.2.1]hept-2-ene, and CO2. The hydroallylation of NBD is accompanied by catalytic addition of formic and acetic acids to one double bond of the diene to give bicyclo[2.2.1]hept-2-en-5-ol and nortricyclan-3-ol acetates and formates. Unlike most known palladium-based catalyst systems, these complexes exhibit catalytic activity also in the absence of phosphines.

Catalytic hydroallylation of norbornadiene with allyl formate

A new catalytic system based on palladium complex compounds for the unconventional allylation of norbornadiene with allylic esters of carboxylic acids is developed. The structure of reaction products is determined and the factors affecting their ratio are found. Comparative analysis of the palladium and nickel catalytic systems is performed.

Unconventional Allylation of Norbornadiene Catalyzed by Palladium Complexes

The reaction of norbornadiene (NBD) with allyl acetate in the presence of the nanocluster Pd147phen32O60(OCOBut)30 (Pd-147; phen is 1,10-phenanthroline) and PPh3 in acetonitrile is nonselective and is accompanied by the decomposition of the cluster, affording the same allylation products of NBD as the reaction with Pd3(OAc)6 or Pd(dba)2 (dba is dibenzylideneacetone) combined with PPh3. In contrast, in the ionic liquid [bmim][BF4] (bmim is 1-butyl-3-methylimidazolinium), the Pd-147 is not decomposed and the reaction occurs selectively to give methylidene(vinyl)norbornene as the sole product. The data obtained suggest that in an ionic liquid, the reaction under study is catalyzed by the nanocluster Pd-147 rather than by the products of its decomposition.

Unusual selective allylation of norbornadiene in the presence of palladium nanoclusters

The catalytic allylation of 7-oxanorbornene, 7-azanorbornene, and bicyclo[2.2.2]octenoic anhydride was performed for the first time. It was found that the structures of allylation products and ratios between them were analogous to those for corresponding carbocyclic derivatives. The presence of a substituent at the double bond of a substrate makes this reaction impossible. Comparative experiments were performed for evaluating the relative reactivity of double bonds in 7-oxanorbornene, 7-azanorbornene, and their carbocyclic analogs.

Unconventional catalytic allylation of 5-norbornene-2,3-dicarboxylic anhydrides: 7-oxa and 7-aza analogues

The optimum conditions are determined for etching latent Kr tracks in sodium hypochlorite solution to prepare polyimide track membranes (PI-TMs) with cylindrical pores and the electrosurface properties of the membranes are investigated. The stability of the porous structure of PI-TMs is studied at elevated temperatures (up to 250°C) in aggressive media (pH 1–12). It is shown that the porous structure of PI-TMs is characterized by enhanced chemical and thermal stability.

V. R. Flid

Papers

Catalytic hydroallylation of norbornadiene with allyl formate

Unconventional Allylation of Norbornadiene Catalyzed by Palladium Complexes

Unusual selective allylation of norbornadiene in the presence of palladium nanoclusters

Unconventional catalytic allylation of 5-norbornene-2,3-dicarboxylic anhydrides: 7-oxa and 7-aza analogues

Pore formation in polyimide irradiated by high-energy ions and the properties of the obtained membranes