8-Hydroxy-5-nitroquinoline as a C-nucleophilic reagent in the reaction of C, C-coupling with quinazoline

The first example of the reaction of 5-nitro-8-hydroxyquinoline as a C-nucleophile with quinazoline is described. As a result of the reaction of C, C-coupling, a stable σ-adduct containing the drug nitroxalin on a heterocyclic carrier was obtained. The structure of the resulting adduct was confirmed by 2D 1H-13C HSQC, 1H-13C HMBC, and 1H-15N HMBC spectra

Comparative analysis of self-aggregation of liquid crystalline Pt(II) complexes in solution and in neat films

Two novel cycloplatinated complexes that differ by the presence/absence of a lateral fused cyclopenteno ring, respectively, were prepared. Although contributing to only a few percentage of the whole molecular volume, the presence of this aliphatic protuberance appears to be essential for the emergence of liquid crystalline behaviour. This pair of two similar compounds, non-mesomorphic complex and mesomorphic complex, was prepared as a model to assess the possible link of the self-aggregation in solution with the appearance of the liquid crystallinity in molten state. NMR dilution studies in CDCl3 solution and X-ray diffusion study in neat films show qualitative similarity of the aggregated structures formed by liquid crystalline complex. Solution studies may therefore be a useful additional tool to the characterization of the liquid crystalline properties and other self-association processes of Pt(II) complexes

Self condensation of enamines mediated by acetylation. A novel approach to 1-(azol-5-yl)-(1E,3Z)-butadiene-4-N,N-dimethylamines

Novel self-condensation of 3-(azol-5-yl)-1,1-dimethylenamines has been found to form new C-C bonds leading to 2,4-(1,2,3-triazole-1,2,3-thiadiazole-3- phenylisothiazole)-(1E,3Z)-5-yl-butadiene-1-amines. The discovered reaction represents a new example of C-H functionalization in unsaturated systems and can serve an efficient synthetic approach to rational design of new 2,4-(diazole-5-yl)-dieneamines. © 2012 The Royal Society of Chemistry

Regioselective synthesis of 5-trifluoromethyl-1,2,3-triazoles via CF 3-directed cyclization of 1-trifluoromethyl-1,3-dicarbonyl compounds with azides

1-Trifluoromethyl-substituted 1,3-dicarbonyl compounds are shown to undergo 100% regioselective cyclization in reactions with alkyl and aryl azides to form 4-acyl-5-trifluoromethyl-1,2,3-triazoles. The reaction represents a general method for the synthesis of otherwise difficulty available 4-acyl-5- trifluoromethyl-1,2,3-triazoles. The directing role of the trifluoromethyl group is discussed in the light of stepwise and concerted mechanisms for this reaction. © 2011 Elsevier Ltd. All rights reserved

15N-Labelling and structure determination of adamantylated azolo-azines in solution

Determining the accurate chemical structures of synthesized compounds is essential for biomedical studies and computer-assisted drug design. The unequivocal determination of N-adamantylation or N-arylation site(s) in nitrogen-rich heterocycles, characterized by a low density of hydrogen atoms, using NMR methods at natural isotopic abundance is difficult. In these compounds, the heterocyclic moiety is covalently attached to the carbon atom of the substituent group that has no bound hydrogen atoms, and the connection between the two moieties of the compound cannot always be established via conventional 1H-1H and 1H-13C NMR correlation experiments (COSY and HMBC, respectively) or nuclear Overhauser effect spectroscopy (NOESY or ROESY). The selective incorporation of 15N-labelled atoms in different positions of the heterocyclic core allowed for the use of 1H-15N (JHN) and 13C-15N (JCN) coupling constants for the structure determinations of N-alkylated nitrogen-containing heterocycles in solution. This method was tested on the N-adamantylated products in a series of azolo-1,2,4-triazines and 1,2,4-triazolo[1,5-a]pyrimidine. The syntheses of adamantylated azolo-azines were based on the interactions of azolo-azines and 1-adamatanol in TFA solution. For azolo-1,2,4-triazinones, the formation of mixtures of N-adamantyl derivatives was observed. The JHN and JCN values were measured using amplitude-modulated 1D 1H spin-echo experiments with the selective inversion of the 15N nuclei and line-shape analysis in the 1D 13С spectra acquired with selective 15N decoupling, respectively. Additional spin–spin interactions were detected in the 15N-HMBC spectra. NMR data and DFT (density functional theory) calculations permitted to suggest a possible mechanism of isomerization for the adamantylated products of the azolo-1,2,4-triazines. The combined analysis of the JHN and JCN couplings in 15N-labelled compounds provides an efficient method for the structure determination of N-alkylated azolo-azines even in the case of isomer formation. The isomerization of adamantylated tetrazolo[1,5-b][1,2,4]triazin-7-ones in acidic conditions occurs through the formation of the adamantyl cation

Switchable Synthesis of 4,5-Functionalized 1,2,3-Thiadiazoles and 1,2,3-Triazoles from 2‑Cyanothioacetamides under Diazo Group Transfer Conditions

High yield solvent-base-controlled, transition metal-free synthesis of 4,5-functionalized 1,2,3-thiadiazoles and 1,2,3-triazoles from 2-cyanothioacetamides and sulfonyl azides is described. Under diazo transfer conditions in the presence of a base in an aprotic solvent 2-cyanothioacetamides operating as C–C–S building blocks produce 5-amino-4-cyano-1,2,3-thiadiazoles exclusively. The use of alkoxide/alcohol system completely switches the reaction course due to the change of one of the reaction centers in the 2-cyanothioacetamide (C–C–N building block) resulting in the formation of 5-sulfonamido-1,2,3-triazole-4-carbothioamide sodium salts as the only products. The latter serve as good precursors for 5-amino-1,2,3-thiadiazole-4-carboximidamides, the products of Cornforth-type rearrangement occurring in neutral protic medium or under acid conditions. According to DFT calculations (B3LYP/6-311+G­(d,p)) the rearrangement proceeds via intermediate formation of a diazo compound, and can be catalyzed by acids via the protonation of oxygen atom of the sulfonamide group