Polyoxa- and Polyazamacrocycles Incorporating 6,7-Diaminoquinoxaline Moiety: Synthesis and Application as Tunable Optical pH-Indicators in Aqueous Solution

Synthetic approach to fluorescent polyaza- and polyoxadiazamacrocycles comprising a structural fragment of 6,7-diamino-2,3-diphenylquinoxaline has been elaborated using Pd-catalyzed amination providing target compounds in yields up to 77%. A series of nine novel N- and N,O-containing macrocyclic ligands differing by the number of donor sites and cavity size has been obtained. These compounds possess well-pronounced fluorescent properties with emission maxima in a blue region in aprotic solvents and high quantum yields of fluorescence, while in proton media, fluorescence shifts towards the green region of the spectrum. Using macrocycles 5c and 5e as examples, we have shown that such compounds can serve as dual-channel (colorimetric and fluorimetric) pH indicators in water media, with pH transition point and response being dependent on the macrocycle structure due to different sequences of protonation steps.

Metal-catalyzed reactions for the C(sp2)–N bond formation: achievements of recent years

The review deals with the main catalytic methods for the C(sp2)–N bond formation, including Buchwald–Hartwig palladium-catalyzed amination of aryl and heteroaryl halides, renaissance of the Ullmann chemistry, i.e., the application of catalysis by copper complexes to form the carbon–nitrogen bond, and Chan–Lam reactions of (hetero)arylboronic acids with amines. Also, oxidative amination with C–H activation, which has been booming during the last decade, is addressed. Particular attention is paid to achievements in the application of heterogenized catalysts.

The bibliography includes 350 references.

Pd(0)-catalyzed amination in the synthesis of chiral derivatives of BINAM and their evaluation as fluorescent enantioselective detectors

A mini-review covers recent successes in the synthesis of (S)-1,1′-binaphthyl-2,2′-diamine (BINAM) using Pd(0)-catalyzed amination reactions. As a result, versatile compounds with C2-chiral backbone were synthesized, among them are derivatives bearing additional chiral amino and fluorophore groups like dansyl amide, 7-methoxycoumarin, 6-aminoquinoline, different macrocyclic compounds with oxadiamine and polyamine linkers were obtained as well. BINAM derivatives of various structures were evaluated as fluorescent enantioselective detectors for a series of model amino alcohols. Many of them were shown to be efficient in sensing certain enantiomers of the amino alcohols by selective changes in the emission in the presence of these analytes. Small changes in the structure of the BINAM derivatives lead to serious difference in the recognition ability of the compounds under investigation.

6-Polyamino-substituted quinolines: synthesis and multiple metal (CuII, HgII and ZnII) monitoring in aqueous media

Chemoselective palladium-catalyzed arylation of polyamines with 6-bromoquinoline has been explored to prepare chelators for the detection of metal cations in aqueous media. The introduction of a single aromatic moiety into non-protected polyamine molecules was achieved using the commercially available Pd(dba)2/BINAP precatalyst to afford nitrogen chelators, in which the aromatic signalling unit is directly attached to the polyamine residue. Water-soluble receptors were then synthesized using N-alkylation of these polyamines by hydrophilic coordinating residues. By combining rich photophysical properties of the 6-aminoquinoline unit with a high coordination affinity of chelating polyamines and a hydrophilic character of carboxamido-substituted phosphonic acid diesters in a single molecular device, we synthesized chemosensor 5 for selective double-channel (UV-vis and fluorescence spectroscopies) detection of CuII ions in aqueous media at physiological levels. This receptor is suitable for the analysis of drinking water and fabrication of paper test strips for the naked-eye detection of CuII ions under UV-light. By increasing the number of donor sites we also obtained chemosensor 6 which is efficient for the detection of HgII ions. Moreover, chemosensor 6 is also suitable for multiple detection of metal ions because it chelates not only HgII but also CuII and ZnII ions displaying different responses of emission in the presence of these three cations.

Synthesis of polymacrocyclic compounds via Pd-catalyzed amination and evaluation of their derivatives as metal detectors

A mini-review is dedicated to the application of Pd(0)-catalyzed amination reactions for the synthesis of polymacrocyclic compounds of various architectures. Such molecules comprise diazacrown ether moieties or structural fragments of tri- and tetraazamacrocycles, polyamine or polyoxadiamine chains of different length and aromatic spacers. Polymacrocyclic compounds thus formed possess an increased number of coordination sites and are suitable for testing as potential receptors of metal cations. Some of these macrocyclic compounds were decorated with the exocyclic dansyl fluorophore group or were coupled with porphyrin units to form polymacrocyclic conjugates. Fluorescent spectra of these compounds were studied in the presence of various metal perchlorates and several macrocycles were found to act as chemosensors or molecular probes for such cations like Cu(II), Al(III), Cr(III).

New trends in the cross-coupling and other catalytic reactions

A mini-review covers the latest achievements in the field of metal-mediated cross-coupling reactions among which are palladium-catalyzed Heck, Suzuki, cyanation and amination reactions. The aspects of the application of Pd nanoparticles (PdNPs) are discussed. The possibilities of the applications of Cu(I)-catalyzed reactions are described. Special emphasis is made on the synthesis of polymacrocyclic compounds like porphyrin dyads and triads, polyazacryptands bearing fluorophore groups using catalytic methods. The application of Pd-catalyzed CH-activation reactions for porphyrin modifications is described, the use of Lewis acids catalysis and organocatalysis for enantioselective C–C bond formation is considered with the emphasis on the application of immobilized organocatalyst.