Browsing by Author "Melo, Teresa M. V. D. Pinho e"
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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.
- Functionalization of dipyrromethanes via hetero-Diels–Alder reaction with azo- and nitrosoalkenesPublication . Pereira, Nelson A. M.; Lemos, A.; Serra, Arménio C.; Melo, Teresa M. V. D. Pinho e5,50-Diethyl- and 5-phenyldipyrromethanes participate in cycloadditions with azo- and nitrosoalkenes giving dipyrromethanes with side chains containing open chain oximes and hydrazones. By controlling reaction stoichiometry it is possible to get mono or 1,9-disubstituted derivatives. The reported methodology gave access to a range of dipyrromethanes with good structural features for various applications. It was demonstrated that reduction of dipyrromethanes containing a-oximino ester groups opens the way to new a-amino esters.
- A hetero-Diels–Alder approach to functionalized 1H-tetrazoles: synthesis of tetrazolyl-1,2-oxazines, -oximes and 5-(1-aminoalkyl)-1H-tetrazolesPublication . Lopes, Susana M. M.; Lemos, A.; Melo, Teresa M. V. D. Pinho eThis work describes the first and unprecedented examples of inverse electron demand Diels–Alder reactions of 5-(1-nitrosovinyl)-1-phenyl-1H-tetrazole, generated in situ from the corresponding bromooxime, with electron rich alkenes and heterocycles, providing in good overall yields tetrazolyl- 1,2-oxazines and -oximes. Upon subsequent reduction these allowed the access to 5-(1-aminoalkyl)- 1H-tetrazoles, paving the way for a new entry into this important class of compounds, bioisosteres of a-amino acids.
- A hetero-Diels-Alder approach to functionalized 1H-tetrazoles: synthesis of tetrazolyl-1,2-oxazines, -oximes and 5-(1-aminoalkyl)-1H-tetrazolesPublication . Lopes, Susana M. M.; Lemos, A.; Melo, Teresa M. V. D. Pinho eThis work describes the first and unprecedented examples of inverse electron demand Diels–Alder reactions of 5-(1-nitrosovinyl)-1-phenyl-1H-tetrazole, generated in situ from the corresponding bromooxime, with electron rich alkenes and heterocycles, providing in good overall yields tetrazolyl-1,2-oxazines and -oximes. Upon subsequent reduction these allowed the access to 5-(1-aminoalkyl)-1H-tetrazoles, paving the way for a new entry into this important class of compounds, bioisosteres of a-amino acids.
- Selective synthesis of 3-(1H-Tetrazol-5-yl)-indoles from 2H-Azirines and ArynesPublication . Grosso, Carla; Alves, Cláudia; Sase, Terver J.; Alves, Nuno G.; Cardoso, Ana L.; Melo, Teresa M. V. D. Pinho e; Lemos, AmericoA new selective synthetic approach to indole derivatives bearing a tetrazole moiety has been developed. Arynes, generated in situ from o-(trimethylsilyl)aryl triflates and KF, reacted smoothly with 2-(2-benzyl-2H-tetrazol-5-yl)-2H-azirines to give 3-(2-benzyl-2H-tetrazol-5-yl)-indole derivatives with high selectivity. Deprotection of the tetrazole moiety gave 3-(1H-tetrazol-5-yl)-indole derivatives.
- 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.