V. V. Syakaev

α-Amino acetals containing a phosphonate or phosphine oxide group. Synthesis and reactions with resorcinols

New α-amino acetals containing a phosphonate or phosphine oxide group were synthesized by the Kabachnik-Fields reaction in the ternary system amino acetal-paraformaldehyde-dialkyl phosphonate (or dialkylphosphine oxide). Condensation of dialkyl (2,2-dimethoxyethylamino)methylphosphonates with resorcinol and its derivatives in ethanol in the presence of hydrochloric acid, apart from the corresponding 2,2-bis(polyhydroxyphenyl) ethylammonium salts, gave 2,5-bis(polyhydroxyphenyl)-1,4-bis[(dialkoxyphosphoryl)methyl]-piperazines. Dialkyl[(2,2-dimethoxyethylamino)methyl]phosphine oxides (Alk = C8H17, C10H21) did not react with resorcinol derivatives under similar conditions, and analogous ammonium salts were obtained by heating the reactants in boiling trifluoroacetic acid.

Facile synthesis of 2-(2-arylpyrrolidin-1-yl)pyrimidines via acid-catalyzed reaction of N-(4,4-diethoxybutyl)pyrimidin-2-amine with phenols

N-(4,4-diethoxybutyl)pyrimidin-2-amine undergoes acid-catalyzed intramolecular cyclisation in the presence of phenols leading to the formation of 2-(2-arylpyrrolidin-1-yl)pyrimidine derivatives. Target compounds were obtained with moderate to good yields by operationally simple one-step procedure.Graphical abstract

Amphiphilic macrocycles bearing biofragment: Molecular design as factor controlling self-assembly

Two novel macrocyclic 6-methyluracilic amphiphiles (uracilophanes) with four (UP1) and two (UP2) uracil moieties and ammonium groups have been synthesized. Tetracationic multi-uracilophane is composed of two macrocyclic units bridged each other with an external methylene spacer, while in the cryptand-like dicationic uracilophane pyrimidinic moieties are connected with an internal methylene spacer. This internal spacer provided a conformational rigidity to the macrocycle. The self-assembly of the uracilophanes is studied and compared with a reference dicationic uracilophane (UP3) with no spacer fragment. Compounds UP1 and UP3 are capable of aggregating, which is characterized by the analogous critical micelle concentration of 1mM, although the former has four decyl tails versus two decyl tails in UP3 molecule. NMR self-diffusion, fluorimetry and DLS techniques revealed that bimodal size distribution occurs in the UP1 solution, with small (≤2nm) and large (ca. 30-50 nm) aggregates contributed. Unexpectedly, the cryptand-like uracilophane UP2 with the same hydrophobicity as UP3 does not form aggregates. The balance of the geometry and energetic factors was analyzed and compared with those contributing to the aggregation of the reference compound UP3. It was established that it is the geometry that controls the packing of the cryptand-like uracilophanes upon aggregation, while hydrophobic effect plays a minor role. In contrast, both factors control the aggregation of oligomeric macrocycle, with energetic factor prevailing. These findings are of importance for (i) the understanding the diverse structural behavior of bioamphiphiles that have very similar chemical structure, but different conformations; and (ii) the design of amphiphiles with controlled model of self-assembly. Supramolecular systems studied can be recommended for biotechnological applications.

Supramolecular catalytic systems based on calix[4]resorcinarene for nucleophilic substitution in phosphorous acid esters

The aggregation and catalytic effect in the reaction of hydrolytic decomposition of phosphorous acid esters are studied for series of systems such as calixarene (CA)-sodium dodecyl sulfate (SDS), CA-poly(ethylene imine) (PEI), SDS-PEI, and CA-SDS-PEI. Using dynamic light scattering, sizes of aggregates are determined, cloud point is estimated, and catalytic effect is studied. Data obtained are consistent with the assumption of the joint aggregation in systems studied. The possibility of the passage from 20-fold inhibiting effect to the catalysis (higher than the order of magnitude) of studied reaction by the immobilization of anionic nanoaggregates (nanoreactors) on a catalytically active polymer matrix is demonstrated. The possibility of the passage from microheterogeneous to heterogeneous system and the separation of catalyst from the products are established.

Effect of Structure of Tetramethyl Sulfonated Calix[4]resorcinarene Aggregates on Paraquat Redox Reactions

The influence of amphiphilic tetramethyl sulfonated calix[4]resorcinarenes with different lengths of hydrophobic tails (R = CH3, C5H11) and trihydroxymethyl amide macrocycle on the behavior of a paraquat in the electrochemical redox process in aqueous solutions is studied. It is revealed that the aggregation of molecules with pentyl substituents makes it possible to partially or completely block the reduction of the paraquat and to resume the redox process depending on the concentration and ratio of components.

Polymethoxyphenyl-substituted [2-(5-chloro-2-hydroxy-4-methylphenyl)-2-phenylvinyl]phosphine oxides: Synthesis and complexation with Eu(TTA)3

New di- and trimethoxyphenyl-substituted phosphorus-containing ligands, (Z)-[2-(5-chloro-2-hydroxy-4-methylphenyl)-2-phenylvinyl]bis(3,4-di- and 3,4,5-trimethoxyphenyl)phosphine oxides, have been synthesized, and their adducts with europium(III) 2-thenoyltrifluoroacetonate have been obtained. High luminescence intensity of the synthesized complexes suggests prospects in using them for the design of various materials possessing unique photophysical properties.

Binding of polar organic substrates by amphiphilic calixresorcin[4]arenes in the solution bulk and on the surface of anion-exchange resin

A comparative study is performed on the binding properties of free and immobilized water-soluble calixresorcin[4]arenes with respect to neutral organic molecules, one of which is capable of forming inclusion complexes, while the other possesses a fairly high potential of many-point hydrogen binding with the groups of the upper rim of macrocycle (parent substances of drugs Xymedon® and Dimephosphon®). It is revealed that macrocycle tetraanions present in aqueous solutions can be electrostatically immobilized on anion-exchange resin Amberlite IRA-900 Cl. The immobilization leads to changes in the binding mechanism of studied substrates due to the formation of calixresorcinarene aggregates on the surface of ion-exchange resin. The sorption of individual substrates and their mixtures is considered and models of the structure of immobilized aggregates of macrocycles and the mechanism of the binding of neutral guest molecules by the aggregates are proposed.

Synthesis of sterically hindered phenolic compounds from indole and its derivatives

Reactions of 3,5-di-tert-butyl-4-hydroxybenzyl acetate with indole and its derivatives gave a series of sterically hindered phenolic compounds having various functional groups. The products are potentially capable of inhibiting radical chain oxidation processes according to different mechanisms.

Aggregation and complexation in a series of tetramethylenesulfonate-substituted calix[4]resorcinarenes

NMR methods are employed to study the effects of inorganic salts, solvents, and guest molecules of methylviologen (MV2+) and choline (Ch+) on the aggregation properties of water-soluble tetramethylene-sulfonate-substituted calix[4]resorcinarenes containing methyl (1), amyl (2), and heptyl (3) substituents in the lower rim. It is established that, in aqueous solutions at concentrations of 1–10 mM, compound 1 exists in the monomeric form; the size of aggregates of amphiphilic compound 2 gradually increases (aggregation number varies from 1 to 20); and hydrophobic compound 3 dissolves only in slightly alkaline aqueous solutions to form large micellar aggregates. For macrocycles 2 and 3, which are inclined to aggregation, the aggregate sizes depend on the concentration, pH, and ionic strength of solutions, as well as on the presence of organic solvents. Macrocycle 1 binds guest molecules Ch+ and MV2+ to yield inclusion complexes. In the presence of aggregates of substance 2, the binding of guest molecules is more efficient and they are encapsulated between the rim of one molecule and the tail of another molecule of compound 2. The presence of guest molecules enhances the aggregation of macrocycle 2. In the case of compound 3 solutions, guest Ch+ molecules are predominantly localized in the hydrophobic environment of alkyl substituents of the host.

Synthesis of new hydrazones based on tetrathiacalix[4]arene in the 1,3-alternate conformation

Reactions of 1,3-alternate stereoisomers of tetrathiacalix[4]arene and 4-tert-butyltetrathiacalix[4]-arene, functionalized by hydrazide groups, with benzaldehyde and pyridin-2-carbaldehyde gave new tetrathiacalix[ 4]arene tetrahydrazone derivatives as promising receptors for transition and toxic heavy metal ions.