20302-26-5Relevant articles and documents
Nucleophilic Aromatic Substitution at Benzene with Powerful Strontium Hydride and Alkyl Complexes
R?sch, Bastian,Gentner, Thomas Xaver,Elsen, Holger,Fischer, Christian A.,Langer, Jens,Wiesinger, Michael,Harder, Sjoerd
supporting information, p. 5396 - 5401 (2019/03/21)
Key to the isolation of the first alkyl strontium complex was the synthesis of a strontium hydride complex that is stable towards ligand exchange reactions. This goal was achieved by using the super bulky β-diketiminate ligand DIPePBDI (CH[C(Me)N-DIPeP]2, DIPeP=2,6-diisopentylphenyl). Reaction of DIPePBDI-H with Sr[N(SiMe3)2]2 gave (DIPePBDI)SrN(SiMe3)2, which was converted with PhSiH3 into [(DIPePBDI)SrH]2. Dissolved in C6D6, the strontium hydride complex is stable up to 70 °C. At 60 °C, H–D isotope exchange gave full conversion into [(DIPePBDI)SrD]2 and C6D5H. Since H–D exchange with D2 is facile, the strontium hydride complex served as a catalyst for the deuteration of C6H6 by D2. Reaction of [(DIPePBDI)SrH]2 with ethylene gave [(DIPePBDI)SrEt]2. The high reactivity of this alkyl strontium complex is demonstrated by facile ethylene polymerization and nucleophilic aromatic substitution with C6D6, giving alkylated aromatic products and [(DIPePBDI)SrD]2.
Directing Reaction Pathways through Controlled Reactant Binding at Pd–TiO2 Interfaces
Zhang, Jing,Wang, Bingwen,Nikolla, Eranda,Medlin, J. Will
, p. 6594 - 6598 (2017/05/29)
Recent efforts to design selective catalysts for multi-step reactions, such as hydrodeoxygenation (HDO), have emphasized the preparation of active sites at the interface between two materials having different properties. However, achieving precise control over interfacial properties, and thus reaction selectivity, has remained a challenge. Here, we encapsulated Pd nanoparticles (NPs) with TiO2 films of regulated porosity to gain a new level of control over catalyst performance, resulting in essentially 100 % HDO selectivity for two biomass-derived alcohols. This catalyst also showed exceptional reaction specificity in HDO of furfural and m-cresol. In addition to improving HDO activity by maximizing the interfacial contact between the metal and metal oxide sites, encapsulation by the nanoporous oxide film provided a significant selectivity boost by restricting the accessible conformations of aromatics on the surface.
Activation of Chlorinated Methanes at the Surface of Nanoscopic Lewis Acidic Aluminum Fluorides
Siwek, Agnieszka K.,Ahrens, Mike,Feist, Michael,Braun, Thomas,Kemnitz, Erhard
, p. 839 - 845 (2017/03/13)
We report on the activation of chlorinated methanes by the heterogeneous catalysts aluminum chlorofluoride (ACF) and high-surface aluminum fluoride (HS-AlF3) under moderate conditions. For comparison, chlorinated toluenes and 1,2-dichloroethane
Organocalcium-mediated nucleophilic alkylation of benzene
Wilson, Andrew S. S.,Hill, Michael S.,Mahon, Mary F.,Dinoi, Chiara,Maron, Laurent
, p. 1168 - 1171 (2017/12/08)
The electrophilic aromatic substitution of a C–H bond of benzene is one of the archetypal transformations of organic chemistry. In contrast, the electron-rich p-system of benzene is highly resistant to reactions with electron-rich and negatively charged organic nucleophiles. Here, we report that this previously insurmountable electronic repulsion may be overcome through the use of sufficiently potent organocalcium nucleophiles. Calcium n-alkyl derivatives—synthesized by reaction of ethene, but-1-ene, and hex-1-ene with a dimeric calcium hydride—react with protio and deutero benzene at 60°C through nucleophilic substitution of an aromatic C–D/H bond. These reactions produce the n-alkyl benzenes with regeneration of the calcium hydride. Density functional theory calculations implicate an unstabilized Meisenheimer complex in the C–H activation transition state.
Hydrophenylation of ethylene using a cationic Ru(ii) catalyst: Comparison to a neutral Ru(ii) catalyst
Burgess, Samantha A.,Joslin, Evan E.,Gunnoe, T. Brent,Cundari, Thomas R.,Sabat, Michal,Myers, William H.
, p. 4355 - 4366 (2015/02/19)
Charge neutral Ru(ii) complexes of the type TpRu(L)(NCMe)Ph [Tp = hydridotris(pyrazolyl)borate; L = CO, PMe3, P(OCH2)3CEt or P(OCH2)2(OCCH3)] have been previously reported to catalyze the hydrophenylation of ethylene (Organometallics, 2012, 31, 6851-6860). However, catalyst longevity for the TpRu(L)(NCMe)Ph complexes is inhibited by competitive ethylene C-H activation. For example, ethylene C-H activation limits catalysis using TpRu(P(OCH2)3CEt)(NCMe)Ph to a maximum of 20 turnover numbers for conversion of benzene and ethylene to ethylbenzene. In contrast, reaction of the cationic Ru(ii) complex [(HC(pz5)3)Ru(P(OCH2)3CEt)(NCMe)Ph][BAr′4] [HC(pz5)3= tris(5-methyl-pyrazolyl)methane; BAr′4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate] (0.025 mol% relative to benzene) in benzene with C2H4(15 psi) at 90 °C gives 565 turnover numbers of ethylbenzene after 131 hours. The production of 565 turnovers of ethylbenzene corresponds to an approximate one-pass 95% yield with ethylene is the limiting reagent and is a 28-fold improvement compared to the charge neutral catalyst TpRu(P(OCH2)3CEt)(NCMe)Ph. Under identical conditions, the activity of [(HC(pz5)3)Ru(P(OCH2)3CEt)(NCMe)Ph][BAr′4] is only 1.3 times less than TpRu(P(OCH2)3CEt)(NCMe)Ph, but the increased stability of the cationic Ru(ii) catalyst allows reactivity at much higher temperatures (up to 175°C) and significantly enhanced rates. This journal is
Catalytic arene H/D exchange with novel rhodium and iridium complexes
Rhinehart, Jennifer L.,Manbeck, Kimberly A.,Buzak, Sara K.,Lippa, Geoffrey M.,Brennessel, William W.,Goldberg, Karen I.,Jones, William D.
experimental part, p. 1943 - 1952 (2012/04/23)
Three novel pendant acetate complexes, [Rh(bdmpza)Cl3] -M+, [Rh(bdmpza)Cl2(py)], and [Ir(bdmpza)Cl3]-M+ (bdmpza = bis(3,5-dimethylpyrazol-1-yl) acetate, M+ = Li+, Na +), were synthesized. Abstraction of halide from these complexes with silver salts yielded species capable of C-H activation of arenes. The catalytic H/D exchange reaction between benzene and trifluoroacetic acid-d was optimized, and these conditions were used to evaluate H/D exchange in other arenes. Branched alkyl substituents in alkyl aromatics showed an affinity toward deuterium exchange in the β-alkyl position only. DFT calculations were performed to determine the mechanism of H/D exchange.
Arene-mercury complexes stabilized by aluminum and gallium chloride: Catalysts for H/D exchange of aromatic compounds
Borovik, Alexander S.,Barron, Andrew R.
, p. 3743 - 3748 (2007/10/03)
Dissolution of Hg(arene)2(MCI4)2 [arene = C6H5Me, C6H5Et, o-C6H4Me2, C6H3-1,2,3-Me3; M = Al, Ga] in C6D6 results in a rapid H/D exchange and the formation of the appropriate dn-arene and C6D5H. H/D exchange is also observed between C6D6 and the liquid clathrate ionic complexes, [Hg(arene)2(MCl4)]-[MCl4], formed by dissolution of HgCl2 and MCl3 in C6H6, m-C6H4Me2, or p-C6H4Me2. The H/D exchange reaction is found to be catalytic with respect to Hg(arene)2(MCl4)2 and independent of the initial arene ligand. Reaction of a 1:1 ratio Of C6H5Me and C6D6 with 6H5Me)2(MCl4)2 results in an equilibrium mixture of all isotopic isomers: C6H5-xDxMe and C6D6-xHx (x = 0-5). DFT calculations on the model system, Hg(C6H6)2(AlCl4)2 and [Hg(C6H6)2(AlCl4)+, show that the charge on the carbon and proton associated with the shortest Hg···C interactions is significantly higher than that on uncomplexed benzene or HgCl2(C6H6)2. The protonation of benzene by either Hg(C6H6)2(AlCl4)2 or [Hg(C6H6)2(AlCl4)]+ was calculated to be thermodynamically favored in comparison to protonation of benzene by HO2CCF3, a known catalyst for arene H/D exchange. Arene exchange and intramolecular hydrogen transfer reactions are also investigated by DFT calculations.
Efficient H-D exchange of aromatic compounds in near-critical D2O catalysed by a polymer-supported sulphonic acid
Boix, Carmen,Poliakoff, Martyn
, p. 4433 - 4436 (2007/10/03)
Hydrogen atom exchange of aromatic compounds in neutral near-critical D2O has been improved by using a polymer-supported sulphonic acid catalyst. Phenol, aniline, quinoline, and substituted aromatic hydrocarbons are selectively ring-perdeuterated in high yields with insignificant by-product formation at 325 °C for 24 h in D2O/Deloxan.
