Guillermo Blustein

A multicomponent protocol for the synthesis of 1,2,5,6-tetrahydropyridines catalyzed by silica-supported phosphomolybdic acid (5PMo@SiO₂) prepared by the sol–gel method was optimized. The influence of temperature and solvent was systematically investigated. The optimized conditions afforded the model tetrahydropyridine in 67% isolated yield after 7 h under reflux in methanol. The methodology was subsequently applied to the synthesis of ten structurally diverse tetrahydropyridine derivatives in moderate-to-good yields (67–77%), demonstrating broad substrate compatibility and good reproducibility upon scale-up. These results highlight the efficiency and versatility of the developed catalytic system for the preparation of functionalized tetrahydropyridines with potential antifouling applications.

Biofouling by mussels is responsible for serious economic losses worldwide. In Argentina, Limnoperna fortunei (Dunker, 1857) and Brachidontes rodriguezii (d’Orbigny, 1842) are common and abundant bivalve species of great interest, inhabiting freshwater and marine coasts, respectively. Both species are considered fouling pests for coastal industrial facilities that use untreated water as part of their processes. To chemically control mussel biofouling, it is necessary to find efficient and environmentally friendly non-biocidal compounds. In this work, we report the antifouling activity of three phenolic compounds (hydroquinone, resorcinol, and catechol) and their respective acetylated derivatives against L. fortunei and B. rodriguezii mussels. Classic ecotoxicity tests with Artemia salina were also performed. Acetylated phenolic compounds were synthesized in the laboratory by sustainable chemistry procedures. Results revealed the importance of hydroquinone, resorcinol, and catechol and their diacetylated derivatives for preventing the settlement of both these mussels, in a non-biocide way. Ecotoxicity bioassays revealed that these compounds were not toxic, with the exception of resorcinol. We propose the incorporation of these compounds in solution into closed circuits and water sprinkler anti-fire systems to prevent the settlement of L. fortunei and their inclusion in antifouling paints to prevent the settlement of B. rodriguezii. These results highlight a new friendly alternative for controlling mussels.

Over the past two decades, polyoxometalates (POM) have received considerable attention as solid catalysts, due to their unique physicochemical characteristics, since, first, they have very strong Bronsted acidity, approaching the region of a superacid, and second, they are efficient oxidizers that exhibit rapid redox transformations under fairly mild conditions. Their structural mobility is also highlighted, since they are complex molecules that can be modified by changing their structure or the elements that compose them to model their size, charge density, redox potentials, acidity, and solubility. Finally, they can be used in substoichiometric amounts and reused without an appreciable loss of catalytic activity, all of which postulate them as versatile, economic and ecological catalysts. Therefore, in 2009, we wrote a review article highlighting the great variety of organic reactions, mainly in the area of the synthesis of bioactive heterocycles in which they can be used, and this new review completes that article with the contributions made in the same area for the period 2010 to 2020. The synthesized heterocycles to be covered include pyrimidines, pyridines, pyrroles, indoles, chromenes, xanthenes, pyrans, azlactones, azoles, diazines, azepines, flavones, and formylchromones, among others.

In this work, the antifouling activity of five alkaloids, isolated from trees of the Atlantic rainforest, was studied. The tested alkaloids were olivacine (1), uleine (2) and N‐methyltetrahydroellipticine (3) from Aspidosperma australe (‘yellow guatambú’) and the furoquinoline alkaloids kokusaginine (4) and flindersiamine (5) from Balfourodendron riedelianum (‘white guatambú’). All these compounds can be isolated from their natural sources in high yields in a sustainable way. The five compounds were subjected to laboratory tests (attachment test of the mussel Mytilus edulis platensis) and field trials, by incorporation into soluble matrix paints, and 45 days of exposure of the painted panels in the sea. The results show that compound 3 is a very potent antifoulant, and that compounds 4 and 5 are also very active, while compounds 1 and 2 did not show any significant antifouling activity. These results open the way for the development of environmentally friendly antifouling agents, based on abundant and easy‐to‐purify compounds that can be obtained in a sustainable way.