89-95-2Relevant articles and documents
Experimental and theoretical study of the effect of active-site constrained substrate motion on the magnitude of the observed intramolecular isotope effect for the P450 101 catalyzed benzylic hydroxylation of isomeric xylenes and 4,4'-dimethylbiphenyl
Audergon, Christian,Iyer, Krishna R.,Jones, Jeffrey P.,Darbyshire, John F.,Trager, William F.
, p. 41 - 47 (1999)
The validity of a cytochrome P450 (P450) 101 force field developed previously was tested by comparing to published results from other laboratories the predicted regioselectivity and stereoselectivity of both (R)- and (S)-norcamphor oxidation when the force field was used. Once validated, the force field was used to test the hypothesis that the magnitude of an observed intramolecular isotope effect is a function of the distance between equivalent but isotopically distinct intramolecular sites of oxidative attack. Molecular dynamics simulations and kinetic deuterium isotope effect experiments on benzylic hydroxylation were then conducted for a series of selectively deuterated isomeric xylenes and 4,4'-dimethylbiphenyl with P450 101. The molecular dynamics simulations predicted that the rank order of substrate mobility in the active site of P450 101 was o-xylene > p- xylene > dimethylbiphenyl. The observed isotope effects for the trideutero analogues were 10.6, 7.4, and 2.7, for the o-xylene, p-xylene, and 4,4'- dimethylbiphenyl, respectively. Thus, as the theoretically predicted rates of interchange between the isotopically distinct methyl groups decrease, the observed isotope effect decreases. The agreement between the theoretical predictions and experimental results provides strong support for the distance hypothesis stated above and for the potential of computational analysis to enhance our understanding of protein/small molecule interactions.
CeO2-nanocubes as efficient and selective catalysts for the hydroboration of carbonyl groups
Bhawar, Ramesh,Bose, Shubhankar Kumar,Patil, Kiran S.
supporting information, p. 15028 - 15034 (2021/09/04)
The CeO2-nanoparticle catalysed hydroboration of carbonyl compounds with HBpin (pin = OCMe2CMe2O) is reported to afford the corresponding borate esters in excellent yield. A series of aromatic and aliphatic aldehydes and ketones having synthetically important functional groups were well-Tolerated under mild reaction conditions. Further, chemoselective hydroboration of aldehydes over other reducible functional groups such as ketone, nitrile, hydroxide, alkene, alkyne, amide, ester, nitro, and halides was achieved. Importantly the catalyst can be recycled up to ten runs with slight loss in activity. This journal is
Uranyl(VI) Triflate as Catalyst for the Meerwein-Ponndorf-Verley Reaction
Kobylarski, Marie,Monsigny, Louis,Thuéry, Pierre,Berthet, Jean-Claude,Cantat, Thibault
supporting information, p. 16140 - 16148 (2021/11/01)
Catalytic transformation of oxygenated compounds is challenging in f-element chemistry due to the high oxophilicity of the f-block metals. We report here the first Meerwein-Ponndorf-Verley (MPV) reduction of carbonyl substrates with uranium-based catalysts, in particular from a series of uranyl(VI) compounds where [UO2(OTf)2] (1) displays the greatest efficiency (OTf = trifluoromethanesulfonate). [UO2(OTf)2] reduces a series of aromatic and aliphatic aldehydes and ketones into their corresponding alcohols with moderate to excellent yields, using iPrOH as a solvent and a reductant. The reaction proceeds under mild conditions (80 °C) with an optimized catalytic charge of 2.3 mol % and KOiPr as a cocatalyst. The reduction of aldehydes (1-10 h) is faster than that of ketones (>15 h). NMR investigations clearly evidence the formation of hemiacetal intermediates with aldehydes, while they are not formed with ketones.
Highly Modular Piano-Stool N-Heterocyclic Carbene Iron Complexes: Impact of Ligand Variation on Hydrosilylation Activity
Nylund, Pamela V. S.,Ségaud, Nathalie C.,Albrecht, Martin
, p. 1538 - 1550 (2021/05/29)
The piano-stool configuration combined with N-heterocyclic carbene (NHC) ligation constitutes an attractive scaffold for employing iron in catalysis. Here, we have expanded this scaffold by installing a pentamethyl cyclopentadienyl (Cp*) ligand as a strong electron donor compared to the traditionally used unsubstituted cyclopentadiene (Cp). Moreover, decarboxylation is introduced as a method to prepare these iron(II) NHC complexes, which avoids the isolation of air-sensitive free carbenes. In addition to the Cp/Cp? variation, the complexes have been systematically modulated at the NHC scaffold, the NHC wingtip groups, and the ancillary ligands in order to identify critical factors that govern the catalytic activity of the iron center in the hydrosilylation of aldehydes. These modulations reveal the importance of steric tailoring and optimization of electron density for high catalytic performance. The data demonstrate a critical role of the NHC scaffold with triazolylidenes imparting consistently higher activity than imidazolylidenes and a correlation between catalytic activity and steric rather than electronic factors. Moreover, the implementation of steric bulk is strongly dependent on the nature of the NHC and severely limited by the Cp? iron precursor. The best performing catalytic systems reach turnover frequencies, TOFmax's, of up to 360 h-1 at 60 °C. Mechanistic investigations by 1H NMR and in situ IR spectroscopies indicate a catalyst activation that involves CO release and aldehyde coordination to the [Fe(Cp)(NHC)I] fragment.
