Into an extended Voorn–Overbeek (EVO) free energy model of polyelectrolyte (PE) complexation and phase behavior, we incorporate three classes of short-ranged electrostatic effects, namely counterion association–dissociation, cross-chain ion pairing (IP), and charge regulation by treating each as a reversible chemical reaction leading to a corresponding law of mass action in a self-consistent fashion. The importance of each reaction is controlled by a corresponding chemistry-dependent standard free energy input parameter. Our model also accounts for Born (or ion solvation) energy using a linear mixing rule for the effective dielectric constant. In monophasic systems, the proposed model can qualitatively explain the observed shifts in acidity and basicity observed in potentiometric titration of weak PEs in the presence of salt and oppositely charged PEs in accordance with Le Châtelier’s principle. We demonstrate how a competition between counterion condensation (CC) and IP alone can explain the complex coac...

A Molecular Thermodynamic Model of Complexation in Mixtures of Oppositely Charged Polyelectrolytes with Explicit Account of Charge Association/Dissociation

Advances in 2H-azirine chemistry: A seven-year update

Cross coupling under transition-metal-free conditions is an attractive and economic alternative to traditional transition-metal-catalysed methods. Metal-free coupling of azaallyls has now been demonstrated with vinyl bromide electrophiles, delivering allylic amines in excellent yields. Moreover, mechanistic evidence supports dual reaction pathways triggered by azaallyl anions and radicals.

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Transition-metal-free chemo- and regioselective vinylation of azaallyls.

This review is devoted to the scientific achievements of the departments of organic chemistry in higher schools of Russia within the past decade.

Modern Trends of Organic Chemistry in Russian Universities

4-Aminopyrrole-3-carboxylates and pyrazine-2-carboxylates were synthesized from 5-alkoxyisoxazoles and 1-sulfonyl-1,2,3-triazoles by tuning the Rh(II) catalyst and the reaction conditions. The reaction in chloroform at 100 °C under Rh2(OAc)4 catalysis provides 4-aminopyrrole-3-carboxylates in good yields. The use of Rh2(Piv)4 in refluxing toluene results in the formation of 1,2-dihydropyrazine-2-carboxylates as the main products, which can be converted by a one-pot procedure to pyrazine-2-carboxylates by heating with catalytic amounts of TsOH. According to the NMR and DFT investigations of the reaction mechanism, pyrroles and dihydropyrazines are formed, respectively, via 1,5- and 1,6-cyclization of common (5Z)-1,4-diazahexa-1,3,5-triene intermediates. The influence of the nature of the catalyst on the product distribution is rationalized in terms of the Rh-catalyzed isomerization of a pyrrolin-2-ylium-3-aminide zwitterion, the primary product of 1,4-diazahexatriene 1,5-cyclization.

Switchable Synthesis of Pyrroles and Pyrazines via Rh(II)-Catalyzed Reaction of 1,2,3-Triazoles with Isoxazoles: Experimental and DFT Evidence for the 1,4-Diazahexatriene Intermediate.

Transformations of 2-azabuta-1,3-dienes, formed in Rh2(OAc)4-catalyzed reactions of diazo carbonyl compounds with 2H-azirines, dramatically depend on the nature of substituents. 4,4-Diphenyl-2-azabuta-1,3-dienes with two electron-acceptor substituents at C1 undergo thermal 1,5-cyclization to give indoles in good yields. The increase in electron-withdrawing ability of C1-substituents facilitates the reaction that proceeds via pseudopericyclic 1,5-electrocyclization of 2-azabutadiene into 7aH-indolium ylide followed by prototropic shift. 3,4-Diphenyl-2-azabuta-1,3-dienes, resulting from reaction of 2,3-diphenyl-2H-azirine and diazo compounds, do not produce indoles via 1,5-cyclization due to the trans-configuration of the 4-Ph-group and the nitrogen, but undergo 1,4-cyclization to 2,3-dihydroazetes. 1,6-Cyclization into 2H-1,4-oxazines with participation of the oxygen of ester or amide group at C1 of corresponding 2-azabuta-1,3-dienes does not take place due to kinetic and thermodynamic reasons. Instead of ...

Pseudopericyclic 1,5- versus Pericyclic 1,4- and 1,6-Electrocyclization in Electron-Poor 4-Aryl-2-azabuta-1,3-dienes: Indole Synthesis from 2H-Azirines and Diazo Compounds.

Nitroethylation of vinyl triflates and bromides.

A molecular thermodynamic model has been proposed that extends the previously known mean field theory of self-association to systems of cross-associating polymers. The extended theory has been applied to model gelation and phase behavior for mixtures of two associating polymers in a good solvent. The gelation threshold is described analytically. Relation between the new theory and SAFT (Macromolecules 2012, 45, 6686−6696 has been established. For ternary systems containing two associating polymers in athermal solvent, simple analytical formula has been obtained for the location of the upper critical consolute point in the long chain limit. Possible types of phase behavior (sol–sol, sol–gel, gel–gel) have been discussed.

Molecular Thermodynamic Modeling of Gelation and Demixing in Solution of Cross-Associating Chains

A two-carbon homologation of vinyl triflates and bromides for the synthesis of homoallylic nitro products is described. This palladium-catalyzed double coupling of nitromethane exploits the anion stabilizing and leaving group properties of nitromethane, generating the homo allyl nitro products via a tandem cross-coupling/π-allylation sequence. The resultant process provides a mild and convenient entry to nitroethylated products, which are versatile precursors to β,γ-unsaturated carbonyls, homoallylic amines, and nitrile oxides.

Nitroethylation of Vinyl Triflates and Bromides.

The Rh(II)-catalyzed coupling reactions of azirines with diazocarbonyl compounds is found to depend on the nature of the azirine and diazocarbonyl substituents.

Pseudopericyclic 1,5‐ versus Pericyclic 1,4‐ and 1,6‐Electrocyclization in Electron‐Poor 4‐Aryl‐2‐azabuta‐1,3‐dienes: Indole Synthesis from 2H‐Azirines and Diazo Compounds.

Sergei Tcyrulnikov

Papers

Pseudopericyclic 1,5- versus Pericyclic 1,4- and 1,6-Electrocyclization in Electron-Poor 4-Aryl-2-azabuta-1,3-dienes: Indole Synthesis from 2H-Azirines and Diazo Compounds.

Nitroethylation of vinyl triflates and bromides.

Molecular Thermodynamic Modeling of Gelation and Demixing in Solution of Cross-Associating Chains

Nitroethylation of Vinyl Triflates and Bromides.

Pseudopericyclic 1,5‐ versus Pericyclic 1,4‐ and 1,6‐Electrocyclization in Electron‐Poor 4‐Aryl‐2‐azabuta‐1,3‐dienes: Indole Synthesis from 2H‐Azirines and Diazo Compounds.