- Pure phosphotriesters as versatile ligands in transition metal catalysis: efficient hydrosilylation of ketones and diethylzinc addition to aldehydes
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This work aims to highlight the underrated role played by pure phosphotriester (or phosphate) ligands in catalysis, when compared to other phosphorus-containing donors such as phosphane oxides or phosphites. To probe this and to enlarge the very narrow catalytic scope of these Lewis bases, easily accessible mono- and bidentate phosphotriesters were tested as donors in two important transition metal-based catalytic transformations: the zinc-catalyzed hydrosilylation of ketones and the titanium-promoted diethylzinc addition to aldehydes. In both cases, the reactions were successful and the corresponding alcohols were obtained in high yields.
- Bouhachicha,Ngo Ndimba,Roisnel,Lalli,Argouarch
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p. 4767 - 4770
(2017/07/11)
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- Synthetic, structural, NMR and catalytic studies of phosphinic amide-phosphoryl chalcogenides (chalcogen = O, S, Se) as mixed-donor bidentate ligands in zinc chemistry
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ortho Substituted (diphenylphosphoryl)-, (diphenylphosphorothioyl)- and (diphenylphosphoroselenoyl)-phosphinic amides o-C6H 4(P(X)Ph2)(P(O)NiPr2) (X = O (20a), S (20b), Se (20c)) were synthesized by ortho directed lithiation of N,N-diisopropyl-P,P-diphenylphosphinic amide (Ph2P(O)N iPr2) followed by trapping with Ph2PCl and subsequent oxidation of the o-(diphenylphosphine)phosphinic amide (19) with H2O2, S8 and Se. The reaction of the new mixed-donor bidentate ligands with zinc dichloride afforded the corresponding complexes [ZnCl2(P(X)Ph2)o-C6H 4(P(O)NiPr2)] (21a-c). The new compounds were structurally characterized in solution by nuclear magnetic resonance spectroscopy and in the solid-state by X-ray diffraction analysis of the ligand (20b) and the three complexes (21a-c). The X-ray crystal structure of 20b suggests the existence of a PO→P(S)-C intramolecular nonbonded interaction. The natural bond orbital (NBO) analysis using DFT methods showed that the stabilization effect provided by a nO→σ* P-C orbital interaction was negligible. The molecular structure of the complexes consisted of seven-membered chelates formed by O,X-coordination of the ligands to the zinc cation. The metal is four-coordinated by binding to the two chlorine atoms showing a distorted tetrahedral geometry. Applications in catalysis revealed that hemilabile ligands 20a-c act as significant promoters of the addition of diethylzinc to aldehydes, with 20a showing the highest activity. Chelation of Et2Zn with 20a was evidenced by NMR spectroscopy.
- Del Aguila-Sanchez, Miguel A.,Santos-Bastos, Neidemar M.,Ramalho-Freitas, Maria C.,Garcia Lopez, Jesus,Costa De Souza, Marcos,Camargos-Resende, Jackson A. L.,Casimiro, Maria,Alves-Romeiro, Gilberto,Iglesias, Maria Jose,Lopez Ortiz, Fernando
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p. 14079 - 14091
(2014/11/12)
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- Synthesis, antifungal activity, and molecular modeling studies of new inverted oxime ethers of oxiconazole
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Some new oxime ethers of types 7 and 8, in which the methyleneaminoxy group, C=N-O, of oxiconazole 6 is in an inverted atomic sequence, were synthesized and tested for their antifungal activities. Among them, the type 7 compounds, such as the N-ethoxy-morpholino-substituted derivatives 71-o (Table 1), showed good antifungal properties against the Candida strains tested, with minimum inhibitory concentration (MIC) values similar to those of the reference drug 6. A remarkable result was obtained with these types of azoles, which had shown a cidal character against Candida albicans, while the reference drug oxiconazole was only fungistatic in the same tests. This fact may be seen from a comparison of the MIC values with those of the minimum fungicidal concentration (MFC) values for most of the type 7 compounds assayed that have shown differences between the MIC and the MFC, which are lower than three double diluitions. A simple molecular modeling of the P450 14-α-sterol demethylase from C. albicans (Candida P450DM) was built in order to understand how the structural differences between type 7 compounds and oxiconazole 6 can induce different antifungal profiles. The results of this work seem to confirm that it is possible to reverse the atomic sequence of the methyleneaminoxy group, C=N-O, of 6, obtaining new imidazoles possessing good antifungal properties.
- Rossello, Armando,Bertini, Simone,Lapucci, Annalina,Macchia, Marco,Martinelli, Adriano,Rapposelli, Simona,Herreros, Esperanza,Macchia, Bruno
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p. 4903 - 4912
(2007/10/03)
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