Browsing by Author "Cardoso, Ana L."
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- Asymmetric neber reaction in the Synthesis of Chiral 2-(Tetrazol-5-yl)-2H-AzirinesPublication . Alves, Claudia; Grosso, Carla; Barrulas, Pedro; Paixao, Jose A.; Cardoso, Ana L.; Burke, Anthony J.; Lemos, Americo; Pinho e Melo, Teresa M. V. D.A successful one-pot methodology for the synthesis of chiral 2-tetrazolyl-2H-azirines has been established, resorting to organocatalysis. The protocol involves the in situ tosylation of beta-ketoxime-1H-tetrazoles followed by the Neber reaction, in the presence of chiral organocatalysts. Among the organocatalysts studied a novel thiourea catalyst derived from 6 beta-aminopenicillanic acid afforded excellent enantioselectivities.
- Hetero-Diels-Alder approach to Bis(indolyl)methanesPublication . Grosso, Carla; Cardoso, Ana L.; Rodrigues, Maria Joao; Marques, Catia; Barreira, Luísa; Lemos, Americo; Pinho e Melo, Teresa M. D. V.A novel synthetic approach to bis(indolyl)methanes has been established. Our one-pot synthetic strategy based on two consecutive hetero-Diels-Alder cycloaddition reactions of electrophilic conjugated nitrosoalkenes with indoles was extended to a range of new 1-hydroxyiminomethyl-bis(indolyl) methanes. Furthermore, a similar and broad range approach was applied to the synthesis of previously unknown 1-hydrazonomethyl-bis(indolyl)methanes. The biological evaluation of the new bis(indolyl) methanes as anti-cancer agents was investigated. (C) 2016 Elsevier Ltd. All rights reserved.
- One-Pot Synthetic Approach to Dipyrromethanes and Bis(indolyl)methanes via Nitrosoalkene ChemistryPublication . Cardoso, Ana L.; Lopes, Susana M. M.; Grosso, Carla; Pineiro, Marta; Lemos, Americo; Pinho e Melo, Teresa M. V. D.A one-pot regio- and stereoselective synthesis of a dipyrromethane and a bis(indolyl)methane based on two consecutive reactions of nitrosoalkenes with pyrrole or indole, respectively, is described as an experiment to be carried out by upper-division undergraduate students in a laboratory classroom. Importantly, the ability of electrophilic conjugated nitrosoalkenes to react via Michael addition or hetero-Diels-Alder reactions with electron-rich heterocycles will provide an opportunity for students to acknowledge alternative reaction pathways underlying certain transformations. Reactions were performed under mild conditions using water as a solvent, followed by purification through column chromatography on silica gel, and characterization of the desired products by NMR and IR spectroscopy. This laboratory experiment combines organic synthesis, determination of the purity of compounds (TLC analysis and melting point measurements), as well as structural analysis (interpretation of 1D NMR spectra). Several important organic chemistry concepts, such as stereo- and regioselectivity, in situ generation and reactivity of conjugated nitrosoalkenes, conjugated 1,4-addition reactions, and cycloaddition reactions, are also discussed.
- 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.