Synthesis of Methyl 4,6-Di-O-ethyl-α-d-glucopyranoside-Based Azacrown Ethers and Their Effects in Asymmetric Reactions

Carbohydrate-based crown ethers have been reported to be able to generate asymmetric induction in certain reactions. Previously, it was proved that the monosaccharide unit, the anomeric substituent, and the sidearm could influence the catalytic activity of the monoaza-15-crown-5 macrocycles derived from sugars. In order to gain information about the effect of the flexibility, 4,6-di-O-ethyl-glucoside-based crown compounds were synthesized, and their efficiency was compared to the 4,6-O-benzylidene analogues. It was found that the absence of the two-ring annulation has a negative effect on the enantioselectivity in liquid-liquid two-phase reactions: in the Darzens condensation of 2-chloroacetophenone and in the epoxidation of chalcone. The same trend was observed in the solid-liquid phase Michael addition of diethyl acetamidomalonate. Surprisingly, in the solid-liquid phase cyclopropanation of benzylidenemalononitrile, one of the new catalysts was highly enantioselective (99% ee).

Carbohydrate-Based Azacrown Ethers in Asymmetric Syntheses

Carbohydrate-based crown ethers represent a special group of chiral phase transfer catalysts. Several derivatives of these macrocycles have been synthesized in our research group. Among these compounds, monoaza-15-crown-5 lariat ethers proved to be effective phase transfer and enantioselective catalysts in certain reactions. Those chiral azacrown ethers incorporating various carbohydrate moieties in the macrocyclic structure are reviewed, which generated asymmetric induction in reactions, such as Michael addition, epoxidation of enones, Darzens condensation and Michael-initiated ring-closure (MIRC) reaction. Effects on the catalytic activity of the structural changes are the focus.

Aminomethylated Hydroxinaphthalenes: Synthesis and Application

The analysis of the literature is carried out and the results of the synthetic approaches to the aminomethylation of hydroxy derivatives of naphthalenes developed over the past 20 years are presented. Most of the described aminomethylation processes proceed as Mannich aminomethylation or, as a special case of a similar condensation --- aminobenzylation according to Betti. The results of all studies are grouped according to the nature of the amine used in the synthesis: primary, secondary, tertiary. Most of the examples were considered for 2-naphthol, however, as the analysis of literature data shows, similar methods are applicable to 1-naphthol and dihydroxynaphthalenes with different positions of OH groups in the ring --- often only the yields of the target product differ. Both the classical methods for the preparation of Mannich and Betti bases using the carbonyl component (formaldehyde, benzaldehyde and its derivatives, respectively) and special cases of synthesis, in which condensation is carried out by means of halogen derivatives, substituted azacrown ethers, etc., are presented. Particular attention is paid to the use of various catalysts and activators, allowing to significantly simplify the synthetic procedures and increase the yields of target compounds. The main fields of application of aminomethylated derivatives of hydroxynaphthalenes are presented

The chemistry of 4-(dicyanomethylene)-3-methyl-l-phenyl-2-pyrazoline-5- ones as a privileged scaffold in synthesis of heterocycles

Background : The reactivity of 4-(dicyanomethylene)-3-methyl-l-phenyl-2-pyrazoline-5-one DCNP 1 and its derivatives makes it valuable as a building block for the synthesis of heterocyclic compounds like pyrazolo-imidazoles, - thiazoles, spiropyridines, spiropyrroles, spiropyrans and others. As a number of publications have reported on the reactivity of DCNP and its derivatives, we compiled some features of this interesting molecule. Objective: This article aims to review the preparation of DCNP, its reactivity and application in heterocyclic and dyes synthesis. Conclusion: In this review we have provided an overview of recent progress in the chemistry of DCNP and its significance in synthesis of various classes of heterocyclic compounds and dyes. The unique reactivity of DCNP offers unprecedentedly mild reaction conditions for the generation of versatile cynomethylene dyes from a wide range of precursors including amines, α-aminocarboxylic acids, their esters, phenols, malononitriles and azacrown ethers. We anticipate that more innovative transformations involving DCNP will continue to emerge in the near future.

Zinc and copper complexes with azacrown ethers and their comparative stability in vitro and in vivo

Radiolabeled macrocyclic zinc complexes are more stable in serum than analogous copper compounds; an azacrown-derived cycle with five heteroatoms coordinates zinc, providing fast complexation and high in vivo stability.

Theoretical study on the binding selectivity of 18-membered azacrown ethers with alkaline earth metal species

The binding selectivity of 18-membered azacrown ethers (monoaza- N1, diaza- N2, triaza- N3, tetraaza- N4, pentaaza- N5, and hexaaza-18-crown-6 N6) with Ca2+, Sr2+, Ba2+ have been studied by density functional theory (DFT) calculations. The complex binding selectivity was analyzed in term of interaction energies, thermodynamic properties, second order interaction energies, and charge transfer effects. The geometrical study shows that Ca2+ and azacrown complexes acquire envelope like structure, leading to shorter bond lengths. As a result, these complex systems have the highest interaction energies. Theoretical study also showed that N6 complex with alkaline earth metal ion were shown to be more stable complex than those ligand with lower nitrogen number. The interaction energy order is N0 < N1 < N2 < N3 < N4 < N5 < N6. This trend shows that the presence of more nitrogen on the crown ether cavity increases the interaction energies by approx. 7.3 % in going from N0 to N6. It is clearly showed that the contribution of the number of nitrogen play a dominant role in the binding selectivity of these systems.

Synthesis of α-d-galactose-based azacrown ethers and their application as enantioselective catalysts in Michael reactions

Crown ethers derived from d-galactose generated good to excellent enantioselectivities in a few Michael reactions under solid–liquid phase transfer conditions.

Reverse hydrotropy by complex formation

Alkylated azacrown ethers lower significantly interfacial tension and are capable of solubilising water-soluble dyes, despite not being able to aggregate in non-polar solvents.