9 documents found, page 1 of 1
Selective synthesis of 3-(1H-Tetrazol-5-yl)-indoles from 2H-Azirines and Arynes
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.
Ethyl 7-Acetyl-8a-methyl-3-(1-phenyl-1H-tetrazol-5-yl)-1,4,4a,5,6,8a-hexahydro-...
Lopes, Susana M. M.; Lemos, Americo; Paixão, José A.; Pinho e Melo, Teresa M. V. D.The Diels–Alder reaction of ethyl 3-(1-phenyl-1<i>H</i>-tetrazol-5-yl-1,2-diaza-1,3-butadiene-1-carboxylate with 2-acetyl-6-methyl-2,3-dihydro-4<i>H</i>-pyran (methyl vinyl ketone dimer) regioselectively afforded the corresponding 3-(tetrazol-5-yl)-hexahydro-7<i>H</i>-pyrano[2,3-<i>c</i>]pyridazine in quantitative yield. An X-ray crystal structure of this cycloadduct is reported.
One-Pot Synthetic Approach to Dipyrromethanes and Bis(indolyl)methanes via Nitr...
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-...
Asymmetric neber reaction in the Synthesis of Chiral 2-(Tetrazol-5-yl)-2H-Azirines
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 ena...
Natural deep eutectic solvents in the hetero-Diels-Alder approach to bis(indoly...
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/glyc...
Regioselectivity in hetero diels-alder reactions
Grosso, Carla; Liber, Marta; Brigas, Amadeu; Pinho e Melo, Teresa M. V. D.; Lemos, AmericoRegioselectivity in hetero Diels-Alder reactions can be observed in a simple reaction between a nonsymmetrical heterodiene and an unsymmetrical heterodienophile. A 9 h and easy to implement laboratory experiment is described, in which students can observe the regioselectivity of inverse "electron-demand" hetero Diels-Alder reactions of an azoalkene with furan or 2,3-dihydrofuran acting as dienophile. This exper...
Hetero-Diels-Alder approach to Bis(indolyl)methanes
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-hydrazonom...
On-water synthesis of dipyrromethanes via bis-hetero-diels–alder reaction of Az...
Pinho e Melo, Teresa; Lemos, Americo; Pereira, Nelson; Lopes, SusanaAn unprecedented one-pot approach to 5-substituted dipyrromethanes based on the hetero-Diels-Alder reaction of azo- and nitrosoalkenes is described. The on-water reaction conditions led to the target compounds in higher yields with significantly shorter reaction times and simpler purification procedures than carrying out the reaction in dichloromethane or in the absence of solvent.
Catalytic epoxidation and sulfoxidation activity of a dioxomolybdenum(VI) compl...
Neves, Patrícia; Gago, Sandra; Pereira, Cláudia C. L.; Figueiredo, Sónia; Lemos, Americo; Lopes, Andre D.; Gonçalves, Isabel S.; Pillinger, MartynA dioxomolybdenum(VI) complex bearing a tetradentate anionic N,O oxazoline ligand with four stereocenters has been studied as a catalyst in the liquid-phase epoxidation of 17 different aliphatic and aromatic olefins(including prochiral, racemate or pure enantiomers) using tert-butyl hydroperoxide as the oxidant. Epoxide selectivities of up to 100% and variable epoxide yields (3–100% within 24 h) were obtained. ...