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During the last two decades, growing interest in the field of material chemistry has been focused on the synthetic design of organic high‐spin molecules for use as novel magnetic materials. Conjugated radicals based on the bis(pyrazolyl)pyridine core are very attractive in principle, since they per se combine optical, chelating and magnetic properties on a single molecular entity. The functionalisation of this core via the bis(4′‐formyl) derivatives with Ullman radicals results in novel functional biradicals, which may further be used for supramolecular architectures. In this paper we describe the synthesis, structure and properties of 2,6‐bis[4′‐(3‐oxo‐1‐oxyl‐4,4,5,5‐tetramethylimidazolin‐2‐yl)pyrazol‐1′‐yl]pyridine (Pz2PyNN) and 2,6‐bis[4‐(1‐oxyl‐4,4,5,5‐tetramethylimidazolin‐2‐yl)pyrazolyl]pyridine (Pz2PyIN). The two biradicals can clearly be differentiated by UV/Vis, IR and EPR spectroscopy. The optical absorptions of the blue Pz2PyNN appear around λmax= 610 nm (ϵ ≈︁ 1700 M−1 cm−1) while for Pz2PyIN the orange‐red colour arises from absorptions at λmax= 468 nm (ϵ ≈︁ 1400 M−1 cm−1). A triplet ground state for the bis(nitronylnitroxide) Pz2PyNN with ΔES‐T ≈︁ 11.8 ± 4.8 cm−1 can be deduced from the EPR studies because of the increase of the double integrated intensity times temperature at very low temperatures, indicating complete population of the triplet state. For the related bis(iminonitroxide) Pz2PyIN a much smaller (at least one order of magnitude lower) singlet−triplet energy gap with an upper limit of 0.7 cm−1 has been derived (0.7 ⪖ ΔES‐T ⪖ −0.07 cm−1). The new multifunctional biradicals represent the first example of high‐spin molecules in the bis(pyrazolyl)pyridine family. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The diazonium salt o f 3-aminopyrazolopyridine when treated with SO: and CuCU produces the corresponding sulphonyl chloride. The sulphonyl chloride chloride easily reacts with hy drazine hydrate, amm onia, aromatic or heterocyclic amines to produce the corresponding sulphohydrazide, sulphonamide or N-sulphonam ide derivatives. Sulphohydrazide reacts with acetylacetone to produce pyrazoly pyrazolopyridinyl sulphone which is also obtained by reac tion o f sulphonyl chloride with dimethylpyrazole. The aminopyrazolopyridine can be converte into pyrazolopyridinthiole by its reacting with ethyl dithioxanthate. The pyrazolopyridinthiole reacts with alkyl halides or acrylonitrile to produce S-alkylated derivatives.

A new series of heteroaromatic polyazomethines containing 1,8-naphthyridine moieties in the polymer backbone were synthesized with a solution polycondensation technique. A new heteroaromatic monomer containing 1,8-naphthyridine moieties (4-ethoxy-2,7-dicarboxaldehyde-1,8-naphthyridine) was synthesized with an analogous synthetic sequence and confirmed by elemental and spectral data. The resulting polymers were characterized by elemental, spectral analyses, solubility and viscometry measurements. All the synthesized polyazomethines had better solubility in polar aportic solvents. The thermal properties of those polymers were evaluated by thermogravimetric analysis, differential thermogravimetry, and differential thermal analysis measurements and correlated to their structural units. All the polymers had nearly similar maximum polymer decomposition temperatures, which were in the range 557-577 C. A very large differ-ence between the glass transitions (92-222 C) was observed. In addition, with gel permeation chromatography, the molecular weight determination of selected examples of those polymers was evaluated. The values of the average molecular weight for polyazomethines 7 b and 7 c were 34,914 and 24,859, respectively. On the other hand, the biological screening of all of the synthesized polyazomethines was performed in variety of bacteria and fungi. Most of the polyazomethines showed a significant influence against Gram-negative bacteria. The minimum inhibitory concentration of the most active polymers was 0.05 mg/mL.

Oxygen-containing heterocycles are largely distributed in natural and synthetic compounds. Coumarins are among the most famous heterocycles which possess one oxygen atom in their rings. Coumarins are classified as multifunctional scaffold and are used as anti-oxidant reagents, anti-inflammatory, anti-microbial, anti-fungal, anti-HIV active, analgesic, anti-histaminic, insecticides, dyes, herbicides, sensitizers, perfumes, cosmetics and food additives. Due to their diverse applications in industrial and pharmaceutical fields, many chemists have given significant interest to these compounds. Herein, the review highlights various methods for the synthesis and interactions of coumarin moiety as one of the most efficient categories of heterocycles.