Direct Amination of Alcohols Catalyzed by Aluminum Triflate: An Experimental and Computational Study.

Among the best-performing homogeneous catalysts for the direct amination of activated secondary alcohols with electron-poor amine derivatives, metal triflates, such as aluminum triflate, Al(OTf)3 , stand out. Herein we report the extension of this reaction to electron-rich amines and activated primary alcohols. We provide detailed insight into the structure and reactivity of the catalyst under working conditions in both nitromethane and toluene solvent, through experiment (cyclic voltammetry, conductimetry, NMR spectroscopy), and density functional theory (DFT) simulations. Competition between aniline and benzyl alcohol for Al in the two solvents explains the different reactivities. The catalyst structures predicted from the DFT calculations were validated by the experiments. Whereas a SN 1-type mechanism was found to be active in nitromethane, we propose a SN 2 mechanism in toluene to rationalize the much higher selectivity observed when using this solvent. Also, unlike what is commonly assumed in homogeneous catalysis, we show that different active species may be active instead of only one

Iron Triflate Salts as Highly Active Catalysts for the Solvent-Free Oxidation of Cyclohexane

International audienceAmong a series of iron salts, iron triflates revealed as highly active catalysts for the oxidation of cyclohexane by tert‐butyl hydroperoxide into cyclohexanol and cyclohexanone with initial turnover frequencies higher than 10,000 h–1. The structure of the iron complexes under the reaction conditions was studied by combining electron paramagnetic resonance (EPR) spectroscopy and DFT calculations. The coordination of the catalytic iron center readily evolved in the presence of the reaction products, leading ultimately to its deactivation. Iron and organic superoxo intermediates were identified as plausible active species allowing to rationalize the high activity of iron ligated by highly delocalized counter‐anions

Direct Amination of Alcohols Catalyzed by Aluminum Triflate: An Experimental and Computational Study

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Respective contributions of α-adrenergic and non-adrenergic mechanisms in the hypotensive effect of imidazoline-like drugs

1. The hypotensive effect of imidazoline-like drugs, such as clonidine, was first attributed to the exclusive stimulation of central α 2-adrenoceptors (α 2ARs). 2. However, a body of evidence suggests that non-adrenergic mechanisms may also account for this hypotension. 3. This work aims (i) to check whether imidazoline-like drugs with no α 2adrenergic agonist activity may alter blood pressure (BP) and (ii) to seek a possible interaction between such a drug and an α 2ARs agonist α-methylnoradrenaline (α-MNA). 4. We selected S23515 and S23757, two imidazoline-like drugs with negligible affinities and activities at α 2ARs but with high affinities for non-adrenergic imidazoline binding sites (IBS). 5. S23515 decreased BP dose-dependently (-27±5% maximal effect) when administered intracisternally (i.c.) to anaesthetized rabbits. The hypotension induced by S23515 (100 μg kg -1 i.c.) was prevented by S23757 (1 mg kg -1 i.c.) and efaroxan (10 μgkg -1 i.c.), while these compounds, devoid of haemodynamic action by themselves, did not alter the hypotensive effect of α-MNA (3 and 30 μg kg -1 i.c.). Moreover, the α 2ARs antagonist rauwolscine (3 μg kg -1 i.c.) did not prevent the effect of S23515. 6. Finally, whilst 3 μg kg -1 of S23515 or 0.5 μg kg -1 of α-MNA had weak hypotensive effects, the sequential i.c. administration of these two drugs induced a marked hypotension (-23±2%). 7. These results indicate that an imidazoline-like drug with no α 2-adrenergic properties lowers BP and interacts synergistically with an α 22ARs agonist.link_to_subscribed_fulltex