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Searching for photoconvertible or photoactivatable dyes, we considered trimethine (Cy3) and pentamethine (Cy5) fluorophores with a 4-amino-1-diazo-2-butanone fragment (H2N(CH2)2COCH=N2) attached to the meso (γ) position of the polymethine chain via the amino group. The Cy3 derivative was prepared. All Cy5 derivatives with the basic amino group at this position decomposed with breaking the polymethine chain. However, amino-squaraine based Cy5 dyes were found to be stable and accessible. Photolysis of Cy3 and squaraine-based Cy5 dyes with a 4-amino-1-diazo-2-butanone fragment was accompanied with Wolff rearrangement and led to pyrrolidones (in methanol and aprotic solvents) formed via intramolecular cyclization of the intermediate ketenes. In aqueous acetonitrile, ketenes reacted with water and gave carboxylic acids. Both products were non-fluorescent, though the model Cy5 dyes (without the squaraine fragment) with acylated amino and N-methylamino groups were found to be fluorescent.

A compact and negatively charged acceptor group, N‐(cyanamino)sulfonyl, is introduced for dye design and its influence on the absorption and emission spectra of the “push–pull” chromophores is demonstrated with 1,3,6‐tris[(cyanamino)sulfonyl]‐8‐aminopyrene. The new sulfonamides, including O‐phosphorylated (3‐hydroxyazetidine)‐N‐sulfonyl, are negatively charged electron acceptors and auxochromes. 1‐Aminopyrenes decorated with the new sulfonamides have three or six negative charges (pH ≥8), low m/z ratios, high mobilities in an electric field, and yellow to orange emission. We labeled maltodextrin oligomers by reductive amination, separated the products by electrophoresis, and demonstrated their high brightness in a commercial DNA analyzer and the distribution of the emission signal among the detection channels., Negatively charged electron acceptors and auxochromes? New sulfonamides make it possible! 1‐Aminopyrenes decorated with the new sulfonamides had low m/z ratios and high mobility in an electric field. Their glycoconjugates with reducing sugars were separated and detected at sub‐picomolar concentration by multicolor emission in a DNA analyzer (see picture).

1‐Aminopyrenes with three ω‐hydroxylated N‐alkylsulfonamido or alkylsulfonyl residues in positions 3, 6, and 8 were prepared, O‐phosphorylated, and applied for reductive amination of oligosaccharides. The dyes (ϵ≈20 000 m −1 cm−1) with six negative charges (pH≥8) and low m/z ratios enable labeling and fluorescence detection of reducing sugars (glycans) related to the most structurally and functionally diverse class of natural products. Under excitation with a 488 nm laser, the new glycoconjugates emit yellow light of about 560 nm, outperforming (with respect to brightness and faster electrophoretic mobilities) the corresponding APTS derivatives (benchmark dye with green emission in conjugates)., Bright 1‐aminopyrenes (ϵ≈20.000 m −1 cm−1) with six negative charges (at pH≥8) and high mobility in the electric field are designed for labeling and fluorescence detection of glycans. The right and left lanes in the figure show the gel electrophoresis bands of new and reference dyes (lowest bands) and their conjugates.

In this work, we developed a simple method for the preparation of N-(3-azido-2-hydroxypropyl)chitosan. We compared the antibacterial activity of N-(3-azido-2-hydroxypropyl)chitosans and previously synthesized N-(2-azidoethyl)chitosans. N-(3-azido-2-hydroxypropyl)chitosans possess higher antibacterial effect which is comparable with that of ampicillin and gentamicin. The effect is due to azido pharmacophore –CH2–CH(OH)–CH2–N3 (for N-(3-azido-2-hydroxypropyl)chitosan) or –CH2–CH2–N3 (for N-(2-azidoethyl)chitosan) introduced in chitosan chain, since the corresponding organic azides NH2–CH2–CH2–N3 and NH2–CH2–CH2–N3 are characterized by high antibacterial activity. However, high antibacterial organic azides NH2–CH2–CH2–N3 and NH2–CH2–CH2–N3 are characterized by high toxicity. Their conjugation to the chitosan chain saves their antibacterial effect, but strongly diminishes their toxicity, and the toxicity of the resulting derivatives is comparable with that of the starting chitosan. These findings are of interest to food science, since novel effective food coatings can be developed on basis of prepared derivatives.

Palladium(II) complexes with chelating and non-chelating diaminocarbene ligands were assessed as catalysts in the cross-coupling reactions of haloarenes with oct-1-yne (Sonogashira reaction) and phenylboronic acid (Suzuki reaction). Both complexes exhibited a higher catalytic activity than traditional phosphine ligandbased systems in the Sonogashira reaction, and they ensured cross-coupling not only with iodoarenes but also with bromoarenes activated by electron-withdrawing substituents. The catalytic activities of the examined complexes in the Suzuki reaction were appreciably different: the palladium(II) complex with the chelating ligand turned out to be considerably less active than the complex with the non-chelating ligand.

Two easily accessible hydrazinoaminocarbene complexes of Pd(II) are shown to be efficient catalysts for copper-free Sonogashira cross-couplings of a variety of aryl iodides with aryl- and alkylalkynes under mild conditions, in ethanol as the solvent and using potassium carbonate as the base. The reactions were carried out with 0.05 mol % of the catalysts which demonstrated exceptional stability in the solid state and in ethanol. Protection from air is not needed. Disubstituted acetylenes were synthesized by the general procedure on up to a gram scale and the yields were 80–98%.

Two easily accessible hydrazinoaminocarbene complexes of Pd(II) are shown to be efficient catalysts for copper-free Sonogashira cross-couplings of a variety of aryl iodides with aryl- and alkylalkynes under mild conditions, in ethanol as the solvent and using potassium carbonate as the base. The reactions were carried out with 0.05 mol % of the catalysts which demonstrated exceptional stability in the solid state and in ethanol. Protection from air is not needed. Disubstituted acetylenes were synthesized by the general procedure on up to a gram scale and the yields were 80–98%.

Cross-coupling reactions of haloarenes with oct-1-yne (Sonogashira reaction) and phenylboronic acid (Suzuki reaction) are presented using palladium(II) complexes with chelating and non-chelating diaminocarbene ligands as catalysts.

Different acyclic diaminocarbene complexes (I)-(III) can be efficiently used under air in an extremely low amount for the Sonogashira coupling of terminal alkynes with benzoyl chlorides.