3010-80-8Relevant academic research and scientific papers
Shuttle arylation by Rh(I) catalyzed reversible carbon–carbon bond activation of unstrained alcohols
Lutz, Marius D.R.,Gasser, Valentina C.M.,Morandi, Bill
supporting information, p. 1108 - 1119 (2021/04/19)
The advent of transfer hydrogenation and borrowing hydrogen reactions paved the way to manipulate simple alcohols in previously unthinkable manners and circumvented the need for hydrogen gas. Analogously, transfer hydrocarbylation could greatly increase the versatility of tertiary alcohols. However, this reaction remains unexplored because of the challenges associated with the catalytic cleavage of unactivated C–C bonds. Herein, we report a rhodium(I)-catalyzed shuttle arylation cleaving the C(sp2)–C(sp3) bond in unstrained triaryl alcohols via a redox-neutral β-carbon elimination mechanism. A selective transfer hydrocarbylation of substituted (hetero)aryl groups from tertiary alcohols to ketones was realized, employing benign alcohols as latent C-nucleophiles. All preliminary mechanistic experiments support a reversible β-carbon elimination/migratory insertion mechanism. In a broader context, this novel reactivity offers a new platform for the manipulation of tertiary alcohols in catalysis.
Determining the Inherent Selectivity for Carbon Radical Hydroxylation versus Halogenation with FeIII(OH)(X) Complexes: Relevance to the Rebound Step in Non-heme Iron Halogenases
Yadav, Vishal,Rodriguez, Rodolfo J.,Siegler, Maxime A.,Goldberg, David P.
supporting information, p. 7259 - 7264 (2020/04/22)
The first structural models of the proposed cis-FeIII(OH)(halide) intermediate in the non-heme iron halogenases were synthesized and examined for their inherent reactivity with tertiary carbon radicals. Selective hydroxylation occurs for these cis-FeIII(OH)(X) (X = Cl, Br) complexes in a radical rebound-like process. In contrast, a cis-FeIII(Cl)2 complex reacts with carbon radicals to give halogenation. These results are discussed in terms of the inherent reactivity of the analogous rebound intermediate in both enzymes and related catalysts.
Facile preparation of aromatic esters from aromatic bromides with ethyl formate or DMF and molecular iodine via aryllithium
Ushijima, Sousuke,Moriyama, Katsuhiko,Togo, Hideo
scheme or table, p. 4701 - 4709 (2012/07/28)
Various aromatic bromides were treated with n-BuLi and subsequently with ethyl formate, followed by the reaction with ethanol and molecular iodine in the presence of K2CO3 to provide the corresponding aromatic ethyl esters in good yields. Moreover, aromatic bromides could be transformed into the corresponding aromatic methyl esters in good yields by the treatment with n-BuLi and subsequently with DMF, followed by the reaction with methanol, molecular iodine, and K2CO3. Some aromatics could be also converted into the corresponding aromatic esters in good yields by the treatment with n-BuLi, and subsequently with ethyl formate or DMF, followed by the reaction with molecular iodine and K2CO3. The present reactions offer a novel route for the transition-metal-free, carbon-monoxide-free, and therefore environmentally benign one-pot conversion of aromatic bromides and aromatics into aromatic esters.
Triarylmethanes and 9-arylxanthenes as prototypes amphihydric compounds for relating the stabilities of cations, anions and radicals by C-H bond cleavage and electron transfer
Arnett, Edward M.,Flowers II, Robert A.,Ludwig, Richard T.,Meekhof, Alison E.,Walek, Stuart A.
, p. 499 - 513 (2007/10/03)
Thermodynamic stability properties of 11 p-substituted trityl and seven 9-phenylxanthyl carbocations are reported in sulfolane and of their conjugate carbanions in DMSO. The cations are compared by calorimetric heats of hydride transfer from cyanoborohydride ion, their first and second reduction potentials, their pK+Rs in aqueous sulfuric acid, 13C chemical shifts and free energies of methoxy exchange. Carbanions are compared by their heats and free energies (pKHA) of deprotonation and their first and second oxidation potentials. Radicals are compared by their oxidation and reduction potentials. Their bond dissociation energies are derived by alternative routes: from the carbocation and its reduction potential and from the carbanion and its oxidation potential. The various properties are correlated against each other and against appropriate Hammett-type substituent parameters. Correlations between the different measured properties reported here range from fair to excellent. Despite their importance as historic prototypes for the three trivalent oxidation states of carbon, trityl and xanthyl systems are atypical models for comparing transmission of electron demand in other series of carbocations, radicals or carbanions with significantly different structures. The 9-arylxanthyl series is especially poor because of its insensitivity to substituent effects. The effects of substituents on various properties which represent the stabilities of R+s correlate surprisingly well against those for corresponding R-s. Accordingly, compensating effects on the oxidation and reduction of a series of related R.s may lead to a nearly constant electron transfer energy and absolute hardness for the series. In contrast, the free energies for interconversion of the carbocations and carbanions which determine the gap between pKR+. and pKHA are very sensitive to structural change.
Thioether complexes of tungsten hexacarbonyl
Lucas, C. Robert
, p. 1758 - 1763 (2007/10/02)
The preparation of a series of organic and organometallic thioethers R3MSR' (M = C,Si,Ge, or Sn) is reported.From these, several new compounds of type 1 are synthesized, some of which contain para-substituted aryl functions for R and R'.In hexane solution in the carbonyl streching region of the ir the uv there is evidence for a degree of multiple bonding, at least in the M - S - WW - CO portion of these molecules.Multiple bonding extending into aromatic R or R'is small or non-existent and cannot be assessed precisely because of spontaneous decomposition of the complexes.All the complexes undergo a thermally initiated decomposition, the case of which depends on the nature of R, R', and M.The unusual W(I) thiolate cis-2 is the termal decomposition product.
One-electron Oxidation of Closed-shell Molecules. Part 4. Acid-induced Oxidative Cleavage of Substituted 1,2,2,2-Tetraphenylethanones (Benzpinacolones) with Diaroyl Peroxides
Kitagawa, Toshikazu,Takeuchi, Ken'ichi,Murai, Osamu,Matsui, Shin,Inoue, Takeshi,Nishimura, Makoto et al.
, p. 1987 - 1996 (2007/10/02)
The acid-induced oxidative cleavage of anispinacolone with diaroyl peroxides in 1,2-dichloroethane-trifluoroacetic acid (TFA) has been investigated.The principal two products after work-up are tris-(p-methoxyphenyl)methanol and p-methoxybenzoic acid; the latter was found as anhydrides in the reaction mixture.Free-radical formation in the course of the cleavage was verified by polymerization of added acrylonitrile in the oxidation by bis-(3,5-dinitrobenzoyl) peroxide.When the oxidation of anispinacolone (90percent (13)C) by dibenzoyl peroxide was carried out in a (13)C n.m.r. probe, an emission peak, assigned to p-methoxybenzoic trifluoroacetic anhydride, was observed.The logarithms of the rate constants for oxidation of p-substituted benzpinacolones by dibenzoyl peroxide were linearly correlated with the oxidation potentials of the benzpinacolones.These results are consistent with a single-electron transfer (s.e.t.) pathway from benzpinacolones to dibenzoyl peroxide.The oxidation is first-order in each reactant and is promoted by TFA.The effect of TFA is accounted for by two factors, (i) assisted O-O bond cleavage of the peroxide radical anion by TFA, and (ii) the formation of protonated peroxide, a more powerful oxidizing species.The former factor is dominant at lower TFA concentrations ( 0.05 M), the latter at higher concentrations.
