CIMO - Posters em Encontros Científicos Internacionais
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- Chromones as versatile building blocks in cycloaddition reactionsPublication . Albuquerque, Hélio; Santos, Clementina M.M.; Cavaleiro, José; Silva, Artur4H-Chromen-4-ones commonly referred as chromones are a class of naturally occurring heterocyclic compounds implicated in a series of biological and pharmacological properties.[1] It is also an interesting scaffold involved in a range of chemical transformations for the preparation of novel and more complex oxygen-containing heterocyclic derivatives.[2] Following our interest in the chemistry of chromones, we design two different building blocks, 2- [(1E,3E)-4-arylbuta-1,3-dien-1-yl]-4H-chromen-4-ones 1 and (E)-2-(4-arylbut-1-en-3-yn-1-yl)-4Hchromen- 4-ones 2, and explore the reactivity of the unsaturated systems in cycloaddition reactions. In the former case, chromones 1 were used as dienes in microwave-assisted Diels–Alder (DA) reactions with various electron-poor and electron-rich dienophiles to provide flavone-type compounds 3.[3] In the latter case, the diene system of chromones 2 was involved in DA reactions with N-methylmaleimide whereas the acetylene moiety react with sodium azide, via 1,3-dipolar cycloaddition reaction, to afford xanthene-1,2,3-triazole dyads 4.[4] In this communication, we will present and discuss the synthetic details and spectroscopic characterization of the main products and some interesting byproducts, as well as the intermediate compounds isolated in each case.
- Conjugate additions of carbon nucleophiles to chromone derivatives towards nitrogen heterocyclesPublication . Albuquerque, Hélio; Santos, Clementina M.M.; Cavaleiro, José; Silva, ArturConjugate additions of nitromethane to the extended π- system of chromone derivatives afforded the 1,6-conjugate addition products, together with structure complex oxygen heterocycles through tandem processes. Further functionalization of targeted adducts allowed the preparation of biological relevant nitrogen heterocycles such as styrylpyrrolidines, as well as pyrazole and bis-pyrazole derivatives.
- Microwave-assisted synthesis of chromeno[3,4-b]xanthones and (benzo[c]cromenyl)chromonesPublication . Albuquerque, Hélio; Santos, Clementina M.M.; Cavaleiro, José; Silva, ArturTwo series of novel propargyloxychromones were designed and synthesized. Both chromone derivatives were used as substrates in MW-assisted intramolecular Diels-Alder reactions, affording chromeno[3,4-b]xanthones and (benzo[c]chromenyl)chromones. This is the first report involving chromone derivatives in intramolecular Diels-Alder reactions for the synthesis of new oxygen heterocycles, namely xanthones and flavones.