Banca de DEFESA: VIVIANE COSTA DE SOUZA
Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.STUDENT : VIVIANE COSTA DE SOUZA
DATE: 28/04/2023
TIME: 14:00
LOCAL: Instituto de química
TITLE:
β-CYCLODEXTRIN THIOGLYCOLIC ESTER DERIVATIVES APPLIED TO A NEW ACCESSIBLE CATALYST FOR SUZUKI-MIYAURA CROSS COUPLING REACTIONS AND SILVER NANOPARTICLE SYNTHESIS
KEY WORDS:
catalyst, β-cyclodextrins, palladium, Suzuki-Miyaura and nanoparticles.
PAGES: 250
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Orgânica
SPECIALTY: Síntese Orgânica
SUMMARY:
Developing simple, selective, efficient and environmentally acceptable catalysts is one of the most important parts of organic synthesis, especially for cross-coupling reactions in forming C-C bonds. The Suzuki-Miyaura coupling reactions are among the most important cross-coupling reactions, but they are inefficient when looking for a reaction with low environmental impact, as they use organic solvents and toxic chemicals as well as the catalyst is difficult to recover. The use of water-soluble supramolecular structures, such as cyclodextrins, as ecologically friendly catalysts has been highlighted in recent years. In this project, a new palladium catalyst was developed, employing β-CD modified with thioglycolic acid and methylated thioglycolic acid as ligands through esterification reactions in a single step. Six different thiolate β-CD derivatives were synthesized (30a-c and 31a-c, yields between 92-97%) were synthesized to study the influence derivatives as ligands on catalyst activity. PdCl2 was chosen as the palladium source. The ligands and the catalyst were characterized by IR, 1H and 13C NMR, TGA, XRD, SEM, MET and mass spectrometry. The catalyst was synthesized in a simple method, in which the ligands and palladium were combined in degassed water at 100 °C for 20 minutes, obtaining palladium nanoclusters with an average diameter of 1.6 nm. This stock solution showed catalytic activity for Suzuki-Miyaura coupling reactions in aqueous medium between aryl halides and aryl boronic acids, using K2CO3 as base and in an open bottle. Different aryl halides were tested, including chlorides, with moderate to excellent yields (39-100%), employing a catalytic amount of 30a/PdCl2 (0.01 mol%). The catalyst can be reused twice before losing catalytic activity. The new catalyst was applied in the coupling reaction between iodinated C8 chrysine and commercial boronic acid, with a reaction time of 18 hours and yield of the new biaryl compound of 84%. The thiolate β-CD derivatives 30a-c and 31a-c were applied in the synthesis of silver nanoparticles, obtaining particles with a diameter of ~2.5 nm to ~35.0 nm, without the addition of reducing agents.
COMMITTEE MEMBERS:
Interno - 2356272 - ARTUR JOSE SANTOS MASCARENHAS
Interno - 1215450 - SILVIO DO DESTERRO CUNHA
Interno - 1276681 - RONAN BATISTA
Interna - 3156252 - LUIZA AMIM MERCANTE
Externo à Instituição - KLEBER THIAGO OLIVEIRA - UFSCAR
Externa à Instituição - SABRINA TEIXEIRA MARTINEZ - UFRJ
Externo à Instituição - CAIO COSTA OLIVEIRA - UNICAMP
Externa à Instituição - IARA DE FÁTIMA GIMENEZ - UFS