Browsing by Author "Palacios, Francisco"
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- [4+2] Cycloadditions of 3-Tetrazolyl-1,2-diaza-1,3-butadienes: synthesis of 3-Tetrazolyl-1,4,5,6-tetrahydropyridazinesPublication . Lopes, Susana M. M.; Brigas, Amadeu; Palacios, Francisco; Lemos, A.; Melo, Teresa M. V. D. Pinho eThe synthesis of new 3-tetrazolyl-1,4,5,6-tetrahydropyridazines by Diels–Alder reactions of ethyl 3-(tetrazol-5-yl)-1,2- diaza-1,3-butadiene-1-carboxylates is reported. These 1,2- diaza-1,3-dienes reacted with electron-rich heterocycles, nucleophilic olefins and cumulenes, as well as with electrondeficient dienophiles, to give the target compounds regioselectively. Computational studies corroborated the rationalization of the observed reactivity and selectivity.
- Diels–Alder reactions of 3-(1H-tetrazol-5-yl)-nitrosoalkenes: synthesis of functionalized 5-(substituted)-1H-tetrazolesPublication . Lopes, Susana M. M.; Palacios, Francisco; Lemos, A.; Melo, Teresa M. V. D. Pinho eA general route to 1,2-oxazines and open chain oximes bearing a 1H-tetrazolyl substituent via DielseAlder reaction of 3-(tetrazol-5-yl)-nitrosoalkenes is reported. It was also demonstrated that reduction of these adducts followed by deprotection of the tetrazolyl group give 5-(1-aminoalkyl)-1H-tetrazoles, a-amino acid analogues.
- Natural deep eutectic solvents in the hetero-Diels-Alder approach to bis(indolyl)methanesPublication . Grosso, Carla; Brigas, Amadeu; de los Santos, Jesus M.; Palacios, Francisco; Lemos, Americo; Pinho e Melo, Teresa M. V. D.For the first time, the use of natural deep eutectic solvents (NADES) as reaction media to carry out hetero-Diels-Alder reactions is disclosed. This allowed to improve the efficiency and sustainability of the synthetic approach to bis(indolyl)methanes (BIMs) based on bis-hetero-Diels-Alder/conjugate addition reactions of nitroso- and azoalkenes with indoles. The ternary mixture of H2O with choline chloride/glycerol allowed the tuning of the physical properties of this NADES leading to a better solvent system, affording the target hydroxyiminomethyl- and hydrazonomethyl-BIMs, in much shorter reaction times, higher efficiency and easier isolation procedures. Furthermore, the direct access to carbonyl-BIMs was possible when 3-methyl-1-tert-butoxycarbonyl azoalkenes were used. [GRAPHICS] .
- The Neber approach to 2-(Tetrazol-5-yl)-2H-AzirinesPublication . Cardoso, Ana Lúcia; Gimeno, Lourdes; Lemos, A.; Palacios, Francisco; Melo, Teresa M. V. D. Pinho eThe synthesis of 2-(tetrazol-5-yl)-2H azirines is reported for the first time. Using the Neber approach, β-ketoxime-1H-tetrazoles were converted into the target 2Hazirines bearing phenyl, furan-2-yl, thiophen-2-yl, or pyrrol-2-yl substituents at C-3. It was demonstrated that the alkaloidmediated Neber reaction allows the asymmetric synthesis of 2-(tetrazol-5-yl)-2H-azirines.