1403668-34-7Relevant academic research and scientific papers
Dendrimeric and Corresponding Monometallic Iridium(III) Catalysts Bound to Carbon Nanotubes Used in Hydroamination Transformations
Pernik, Indrek,Desmecht, Antonin,Messerle, Barbara A.,Hermans, Sophie,Riant, Olivier
, p. 3448 - 3457 (2021)
This report describes the synthesis of a carbon nanotube-bound dendrimer and three carbon nanotube-bound monometallic complexes and their use as catalysts. The polyamidoamine third generation dendrimer used here incorporates pyrazole-triazole moieties suitable for ligating iridium(III) centres. The monometallic complexes use the same pyrazole-triazole ligands coordinated to an iridium(III) centre. All catalysts were characterized using ICP-AES and XPS to evaluate their metal loadings on the carbon surface with significantly higher relative weight percentage of iridium determined for the denrimeric species. The catalytic activity and practicality of the formed catalysts were tested using two different intramolecular hydroamination reactions.
Catalyzed tandem C-N/C-C bond formation for the synthesis of tricyclic indoles using Ir(III) pyrazolyl-1,2,3-triazolyl complexes
Wong, Chin Min,Vuong, Khuong Q.,Gatus, Mark R. D.,Hua, Carol,Bhadbhade, Mohan,Messerle, Barbara A.
, p. 7500 - 7510 (2013/01/15)
A series of new pyrazolyl-1,2,3-triazolyl N-N′ bidentate donor ligands (2a-c, 3a-d) were prepared via Cu(I)-catalyzed Huisgen cycloaddition reactions between 1-propargylpyrazoles and 4-substituted phenyl azides. The electron-withdrawing ability of the substituents follows the trend PhCH 2 3Ph 3Ph 2Ph, as illustrated in the gradual downfield shift of the 1,2,3-triazolyl-C4′ 13C NMR resonances. A series of Rh and Ir complexes containing these pyrazolyl-1,2,3-triazolyl or bis(pyrazol-1-yl)methane donor ligands of general formulae [Ir(N-N′)Cp*Cl]X (X = BAr F4, BPh4; 5-8), [Rh(N-N′)Cp*Cl]X (X = BArF4, BPh4; 9-11), and [Rh(N-N′)(CO) 2]BArF4 (13-16) (BArF4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) were synthesized and fully characterized. The solid-state structures of 5, 6a′, 6b, 7b, 8, 9, 10a, 10a′, 11, and 15c were determined by X-ray diffraction studies. As the electron-withdrawing strength of the phenylene substituent on the triazolyl ring is increased, the M-N3′(triazole) bond length becomes longer. The efficiency of these Rh and Ir complexes as catalysts for the synthesis of tricyclic indoles via tandem C-N and C-C bond formation reactions from 2-(hydroxyalk-1-ynyl)anilines (17S-20S) was assessed. The Ir(III) catalysts were the most efficient for the C-C bond formation step, and the Rh(I) complexes 13-16 were the most efficient catalysts for C-N bond formation, where TOFs >1000 h-1 were reached. However, the Ir(III) complexes 5-8 were found to be the only active catalysts for the tandem C-N and C-C bond formation, as the Rh(I) complexes were not active catalysts for the C-C bond formation step. The C-N bond formation leading to the formation of indoles was found to proceed via two reaction pathways with 2-(hydroxyalk-1-ynyl)aniline substrates: (a) hydroamination and (b) hydroalkoxylation-Lewis acid mediated isomerization. Pathway (b) is likely to be the main pathway in the formation of indoles starting with 2-(hydroxyalk-1-ynyl)aniline substrates 17S, 18S, and 20S.
