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

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

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

Suzuki–Miyaura coupling of aryl fluorosulfates in water: a modified approach for the synthesis of novel coumarin derivatives under mild conditions

We herein report a modified, eco-friendly and atom-economical approach for the synthesis of a series of novel coumarin analogues via Suzuki–Miyaura cross-coupling methodology under mild conditions. The utilization of coumarin fluorosulfate as an atom-economical pseudohalide based electrophilic coupling partner was the key for success of our modified methodology. In addition, the use of water as a solvent, exceptionally milder reaction conditions and traditional catalytic systems further demonstrates the synthetic utility of the developed protocol. A comparative study of different pseudohalide leaving groups has been carried out in the later stage to understand the efficiency of aryl fluorosulfate. From this study, the increased hydrophilic nature of the fluorosulfate electrophilic coupling partner when compared to the other electrophiles has been realized. This allowed the increased solubility of the fluorosulfate electrophile in water under milder temperature conditions thereby furnishing the desired products in good to excellent yields

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