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A sorbent based on gold nanoparticles deposited by direct reduction of a gold salt on a structured carbon surface has been prepared to be used in the mercury capture at low concentrations. A total of 13 samples have been obtained varying preparation conditions (stirring rate, gold salt concentration and contact time). A kinetic study of the gold reduction on the carbon surface has been carried out, indicating that the calculated reaction rate constant corresponds to the diffusion rate equation. The study of the influence of gold salt concentration on the reduction potential of the gold showed that the use of a high concentration gold salt solution shifts the reduction reaction to gold reduction. Mercury capture capacity cannot be directly related with either gold content or average particle size or average crystal size, but the study of the grain size distribution can explain the mercury capture performance of the samples.

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The reaction between pyridones (1) and substituted hydrazines 4 can afford two different regioisomeric pyrazolo[3,4‐b]pyridin‐6‐ones 2 and 3 depending on the initial substitution of the methoxy group and the direction of the cyclization. In the case of phenylhydrazine 4 (R3 = Ph), we have clearly shown that the treatment of pyridones 1a–d with 4 (R3 = Ph) in MeOH at temperatures below 140°C yields, independently of the nature and position of the substituents present in the pyridone ring, the open intermediates 7a–d. When the reaction is carried at 140°C under microwave irradiation, the corresponding 2‐aryl substituted pyrazolo[3,4‐b]pyridines 3a–d are always formed. We have experimentally determined, using DSC techniques, the activation energies of the two steps involved in the formation of 3: a) substitution of the methoxy group present in pyridones 1 with phenylhydrazine 4 (R3 = Ph) to afford intermediates 7 and b) cyclization of intermediates 7 to yield pyrazolopyridines 3. The results obtained, 15 and 42 kcal⋅mol−1 respectively, are in agreement with the experimental findings.