484-66-2Relevant articles and documents
Incl34h2o-catalyzed trioxane as a new methylating agent for multi-methylated aromatics affording hexamethyl benzene
Chen, Song-Jie,Hua, Ruimao
, p. 61 - 63 (2010)
In the presence of a catalytic amount of InCl3-4H2O, trioxane was first used as the methylating agent for multi- methylated aromatic compounds such as pentamethylbenzene, 1,2,4,5-tetramethylbenzene and 1,3,5-trimethylbenzene to afford hexamethylbenzene in fair to high yields.
Photocatalytic Oxygenation Reactions with a Cobalt Porphyrin Complex Using Water as an Oxygen Source and Dioxygen as an Oxidant
Hong, Young Hyun,Han, Ji Won,Jung, Jieun,Nakagawa, Tatsuo,Lee, Yong-Min,Nam, Wonwoo,Fukuzumi, Shunichi
supporting information, p. 9155 - 9159 (2019/06/21)
Photocatalytic oxygenation of hexamethylbenzene occurs under visible-light irradiation of an O2-saturated acetonitrile solution containing a cobalt porphyrin complex CoII(TPP) (TPP2- = tetraphenylporphyrin dianion), water, and triflic acid (HOTf) via a one-photon-two-electron process, affording pentamethylbenzyl alcohol and hydrogen peroxide as products with a turnover number of >6000; in this reaction, H2O and O2 were used as an oxygen source and a two-electron oxidant, respectively. The photocatalytic mechanism was clarified by means of electron paramagnetic resonance, time-resolved fluorescence, and transient absorption measurements as well as 18O-labeling experiments with H218O and 18O2. To the best of our knowledge, we report the first example of efficient photocatalytic oxygenation of an organic substrate by a metal complex using H2O as an oxygen source and O2 as a two-electron oxidant.
Photocatalytic Oxygenation of Substrates by Dioxygen with Protonated Manganese(III) Corrolazine
Jung, Jieun,Neu, Heather M.,Leeladee, Pannee,Siegler, Maxime A.,Ohkubo, Kei,Goldberg, David P.,Fukuzumi, Shunichi
, p. 3218 - 3228 (2016/05/02)
UV-vis spectral titrations of a manganese(III) corrolazine complex [MnIII(TBP8Cz)] with HOTf in benzonitrile (PhCN) indicate mono- and diprotonation of MnIII(TBP8Cz) to give MnIII(OTf)(TBP8Cz(H)) and [MnIII(OTf)(H2O)(TBP8Cz(H)2)][OTf] with protonation constants of 9.0 × 106 and 4.7 × 103 M-1, respectively. The protonated sites of MnIII(OTf)(TBP8Cz(H)) and [MnIII(OTf)(H2O)(TBP8Cz(H)2)][OTf] were identified by X-ray crystal structures of the mono- and diprotonated complexes. In the presence of HOTf, the monoprotonated manganese(III) corrolazine complex [MnIII(OTf)(TBP8Cz(H))] acts as an efficient photocatalytic catalyst for the oxidation of hexamethylbenzene and thioanisole by O2 to the corresponding alcohol and sulfoxide with 563 and 902 TON, respectively. Femtosecond laser flash photolysis measurements of MnIII(OTf)(TBP8Cz(H)) and [MnIII(OTf)(H2O)(TBP8Cz(H)2)][OTf] in the presence of O2 revealed the formation of a tripquintet excited state, which was rapidly converted to a tripseptet excited state. The tripseptet excited state of MnIII(OTf)(TBP8Cz(H)) reacted with O2 with a diffusion-limited rate constant to produce the putative MnIV(O2?-)(OTf)(TBP8Cz(H)), whereas the tripseptet excited state of [MnIII(OTf)(H2O)(TBP8Cz(H)2)][OTf] exhibited no reactivity toward O2. In the presence of HOTf, MnV(O)(TBP8Cz) can oxidize not only HMB but also mesitylene to the corresponding alcohols, accompanied by regeneration of MnIII(OTf)(TBP8Cz(H)). This thermal reaction was examined for a kinetic isotope effect, and essentially no KIE (1.1) was observed for the oxidation of mesitylene-d12, suggesting a proton-coupled electron transfer (PCET) mechanism is operative in this case. Thus, the monoprotonated manganese(III) corrolazine complex, MnIII(OTf)(TBP8Cz(H)), acts as an efficient photocatalyst for the oxidation of HMB by O2 to the alcohol.
Switchover of the Mechanism between Electron Transfer and Hydrogen-Atom Transfer for a Protonated Manganese(IV)–Oxo Complex by Changing Only the Reaction Temperature
Jung, Jieun,Kim, Surin,Lee, Yong-Min,Nam, Wonwoo,Fukuzumi, Shunichi
supporting information, p. 7450 - 7454 (2016/07/06)
Hydroxylation of mesitylene by a nonheme manganese(IV)–oxo complex, [(N4Py)MnIV(O)]2+(1), proceeds via one-step hydrogen-atom transfer (HAT) with a large deuterium kinetic isotope effect (KIE) of 3.2(3) at 293 K. In contrast, the same reaction with a triflic acid-bound manganese(IV)-oxo complex, [(N4Py)MnIV(O)]2+-(HOTf)2(2), proceeds via electron transfer (ET) with no KIE at 293 K. Interestingly, when the reaction temperature is lowered to less than 263 K in the reaction of 2, however, the mechanism changes again from ET to HAT with a large KIE of 2.9(3). Such a switchover of the reaction mechanism from ET to HAT is shown to occur by changing only temperature in the boundary region between ET and HAT pathways when the driving force of ET from toluene derivatives to 2 is around ?0.5 eV. The present results provide a valuable and general guide to predict a switchover of the reaction mechanism from ET to the others, including HAT.
Light-Driven, Proton-Controlled, Catalytic Aerobic C-H Oxidation Mediated by a Mn(III) Porphyrinoid Complex
Neu, Heather M.,Jung, Jieun,Baglia, Regina A.,Siegler, Maxime A.,Ohkubo, Kei,Fukuzumi, Shunichi,Goldberg, David P.
supporting information, p. 4614 - 4617 (2015/04/27)
The visible light-driven, catalytic aerobic oxidation of benzylic C-H bonds was mediated by a MnIII corrolazine complex. To achieve catalytic turnovers, a strict selective requirement for the addition of protons was established. The resting state of the catalyst was unambiguously characterized by X-ray diffraction as [MnIII(H2O)(TBP8Cz(H))]+, in which a single, remote site on the ligand is protonated. If two remote sites are protonated, however, reactivity with O2 is shut down. Spectroscopic methods revealed that the related MnV(O) complex is also protonated at the same remote site at -60 °C, but undergoes valence tautomerization upon warming.
Unified view of oxidative C-H bond cleavage and sulfoxidation by a nonheme iron(IV)-oxo complex via lewis acid-promoted electron transfer
Park, Jiyun,Morimoto, Yuma,Lee, Yong-Min,Nam, Wonwoo,Fukuzumi, Shunichi
supporting information, p. 3618 - 3628 (2014/05/06)
Oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by a nonheme iron(IV)-oxo complex, [(N4Py)Fe IV(O)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine), were remarkably enhanced by the presence of triflic acid (HOTf) and Sc(OTf)3 in acetonitrile at 298 K. All the logarithms of the observed second-order rate constants of both the oxidative C-H bond cleavage and sulfoxidation reactions exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes between PCET and MCET were taken into account, respectively. Thus, the mechanisms of both the oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by [(N4Py)FeIV(O)]2+ in the presence of HOTf and Sc(OTf)3 have been unified as the rate-determining electron transfer, which is coupled with binding of [(N4Py)FeIV(O)]2+ by proton (PCET) and Sc(OTf)3 (MCET). There was no deuterium kinetic isotope effect (KIE) on the oxidative C-H bond cleavage of toluene via the PCET pathway, whereas a large KIE value was observed with Sc(OTf)3, which exhibited no acceleration of the oxidative C-H bond cleavage of toluene. When HOTf was replaced by DOTf, an inverse KIE (0.4) was observed for PCET from both toluene and [Ru II(bpy)3]2+ (bpy =2,2′-bipyridine) to [(N4Py)FeIV(O)]2+. The PCET and MCET reactivities of [(N4Py)FeIV(O)]2+ with Bronsted acids and various metal triflates have also been unified as a single correlation with a quantitative measure of the Lewis acidity.
Chlorination of benzylic and allylic alcohols with trimethylsilyl chloride enhanced by natural sodium montmorillonite
Tandiary, Michael Andreas,Masui, Yoichi,Onaka, Makoto
supporting information, p. 2639 - 2643 (2015/01/09)
A new and practical method for the efficient chlorination of tertiary, secondary, and primary benzylic and allylic alcohols is described. The method is characterized by the formation of hydrogen chloride from trimethylsilyl chloride and trace water, the formation of a carbenium ion through the protonation of an alcohol and subsequent dehydration, and the chlorination of the carbenium ion. During the process, sodium ion-exchanged montmorillonite plays a crucial role in capturing the generated hydrogen chloride, stabilizing the carbenium intermediate as well as promoting the chlorination.
Bronsted acid-promoted C-H bond cleavage via electron transfer from toluene derivatives to a protonated nonheme iron(IV)-oxo complex with no kinetic isotope effect
Park, Jiyun,Lee, Yong-Min,Nam, Wonwoo,Fukuzumi, Shunichi
supporting information, p. 5052 - 5061 (2013/06/04)
The reactivity of a nonheme iron(IV)-oxo complex, [(N4Py)Fe IV(O)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine), was markedly enhanced by perchloric acid (70% HClO4) in the oxidation of toluene derivatives. Toluene, which has a high one-electron oxidation potential (Eox = 2.20 V vs SCE), was oxidized by [(N4Py)FeIV(O)]2+ in the presence of HClO4 in acetonitrile (MeCN) to yield a stoichiometric amount of benzyl alcohol, in which [(N4Py)FeIV(O)]2+ was reduced to [(N4Py)Fe III(OH2)]3+. The second-order rate constant (kobs) of the oxidation of toluene derivatives by [(N4Py)Fe IV(O)]2+ increased with increasing concentration of HClO4, showing the first-order dependence on [HClO4]. A significant kinetic isotope effect (KIE) was observed when mesitylene was replaced by mesitylene-d12 in the oxidation with [(N4Py)Fe IV(O)]2+ in the absence of HClO4 in MeCN at 298 K. The KIE value drastically decreased from KIE = 31 in the absence of HClO4 to KIE = 1.0 with increasing concentration of HClO4, accompanied by the large acceleration of the oxidation rate. The absence of KIE suggests that electron transfer from a toluene derivative to the protonated iron(IV)-oxo complex ([(N4Py)FeIV(OH)]3+) is the rate-determining step in the acid-promoted oxidation reaction. The detailed kinetic analysis in light of the Marcus theory of electron transfer has revealed that the acid-promoted C-H bond cleavage proceeds via the rate-determining electron transfer from toluene derivatives to [(N4Py)FeIV(OH)] 3+ through formation of strong precursor complexes between toluene derivatives and [(N4Py)FeIV(OH)]3+.
Hydrogen-bonded helical self-assembly of sterically-hindered benzyl alcohols: Rare isostructurality and synthon equivalence between alcohols and acids
Moorthy, Jarugu Narasimha,Mandal, Susovan,Venugopalan, Paloth
scheme or table, p. 2942 - 2947 (2012/09/07)
Hydrogen-bonded aggregation has been examined in a series of sterically hindered benzyl alcohols with an objective to explore how sterics influence the otherwise inconsistent and variable synthons generally observed for alcohols. All the sterically hindered alcohols 8-15 were found to adopt a helical hydrogen-bonded synthon, and crystallize uniformly in the rare I41/a space group, for which the statistical prevalence in the CSD is abysmally small. Remarkably, the crystal packing in all of these alcohols is found to be isostructural to analogous sterically hindered carboxylic acids 1-4. The reason as to why all alcohols sustain the helical motif, despite being aggregated via rather weak hydrogen bonds as compared those in analogous acids 1-4 is traceable to unique molecular topology that permits close-packing as well as exploitation of intermolecular interactions comprehensively. It is shown that sterics permit a very rare packing as well as synthon equivalence between carboxylic acids and alcohols. It emerges from the present study that the hydrogen-bonded synthons of strongly interacting functional groups are not necessarily reproducible when sterics are brought into picture. By the same token, the synthons may sustain even when the interactions are weak when close packing is ensured.
Scandium ion-promoted photoinduced electron transfer from electron donors to acridine and pyrene. Essential role of scandium ion in photocatalytic oxygenation of hexamethylbenzene
Fukuzumi, Shunichi,Yuasa, Junpei,Satoh, Naoya,Suenobu, Tomoyoshi
, p. 7585 - 7594 (2007/10/03)
Photoinduced electron transfer from a variety of electron donors including alkylbenzenes to the singlet excited state of acridine and pyrene is accelerated significantly by the presence of scandium trifiate [Sc(OTf)3] in acetonitrile, whereas no photoinduced electron transfer from alkylbenzenes to the singlet excited state of acridine or pyrene takes place in the absence of Sc(OTf)3. The rate constants of the Sc(OTf)3-promoted photoinduced electron-transfer reactions (ket) of acridine to afford the complex between acridine radical anion and Sc(OTf)3 remain constant under the conditions such that all the acridine molecules form the complex with Sc(OTf)3. In contrast to the case of acridine, the ket value of the Sc(OTf)3-promoted photoinduced electron transfer of pyrene increases with an increase in concentration of Sc(OTf)3 to exhibit first-order dependence on [Sc(OTf)3] at low concentrations, changing to second-order dependence at high concentrations. The first-order and second-order dependence of ket on [Sc(OTf)3] is ascribed to the 1:1 and 1:2 complexes formation between pyrene radical anion and Sc(OTf)3. The positive shifts of the one-electron redox potentials for the couple between the singlet excited state and the ground-state radical anion of acridine and pyrene in the presence of Sc(OTf)3 as compared to those in the absence of Sc(OTf)3 have been determined by adapting the free energy relationship for the photoinduced electron-transfer reactions. The Sc(OTf)3-promoted photoinduced electron transfer from hexamethylbenzene to the singlet excited state of acridine or pyrene leads to efficient oxygenation of hexamethylbenzene to produce pentamethylbenzyl alcohol which is further oxygenated under prolonged photoirradiation of an O 2-saturated acetonitrile solution of hexamethylbenzene in the presence of acridine or pyrene which acts as a photocatalyst together with Sc(OTf)3. The photocatalytic oxygenation mechanism has been proposed based on the studies on the quantum yields, the fluorescence quenching, and direct detection of the reaction intermediates by ESR and laser flash photolysis.
