5623-45-0Relevant articles and documents
A DIPOLE MOMENT STUDY OF HINDERED BENZOPHENONES
Lumbroso, H.,Liegeois, Ch.,Goethals, G.,Uzan, R.
, p. 133 - 146 (1989)
Dipole moment analysis of 4-X-2,6-dimethylbenzophenones, 4'-X-2,6-dimethyl- and 4'-X-2,4,6-trimethylbenzophenones, with X=OMe and X=NMe2, showed that the (X...C=O) interaction moments are much lower in the first family of compounds. 2,6-Dimethyl-, and 2,4,6-trimethylbenzophenone exhibit an asymmetric gauche model with φ=55 deg and φ'=0 deg. 2,6-Dimethyl-3'-chloro- and 2,4,6-trimethyl-3'-chlorobenzophenones occur as equimolecular mixtures of cis-(Cl,O) and trans-(Cl,O) conformers.Preferred conformations are proposed for p-chloro, p-methoxy- and p-dimethylaminobenzophenone, and the delicate problem posed by the actual conformation of benzophenone in solution is discussed.In the present work, 25 benzophenones were examined, and their dipole moments were analysed according to a coherent pattern.
Dimesitylketone O-oxide: Spectroscopic characterization, conformation, and reaction modes: OH formation and OH capture
Sander,Block,Kappert,Kirschfeld,Muthusamy,Schroeder,Sosa,Kraka,Cremer
, p. 2618 - 2627 (2001)
Dimesitylketone O-oxide 1b was synthesized by photolysis of dimesityldiazomethane dissolved in an oxygen saturated CCl3F solution at 140 K. Conformation and geometry of 1b were determined by comparing measured NMR chemical shifts with the corresponding chemical shifts calculated at the DFT-IGLO level of theory where it had to be considered that the molecule exists in two enantiomeric forms. Measured and calculated 1H chemical shifts agree within 0.1 ppm while the calculated 13C shift of the COO carbon (210.6 ppm) differs by only 0.4 ppm from the measured shift of 211.0 ppm. The two mesityl rings are perpendicular to each other and enclose angles of 40 and 57° with the COO plane. The preferred rearrangement process of 1b is an H migration from one of the ortho-methyl groups to the terminal O atom of the COO unit. The calculated activation enthalpy of this process is 12.7 kcal/mol (B3LYP/cc-pVTZ). In contrast, the activation enthalpy for isomerization to dioxirane is 5 kcal/mol higher. In CCl3F, the activation barrier for the thermal decay was determined to be 13.8 ± 0.2 kcal/mol and in acetonitrile 13.1 ± 0.4 kcal/mol. H migration initiates cleavage of the OO bond and the production of an OH and a benzyl radical. Recombination of the latter in the solvent cage leads to the formation of 2-methylhydroxy-pentamethylbenzophenone, while escape of the OH radical from the solvent cage yields a ketone. These results confirm the possibility of OH production from carbonyl oxides in the solution phase.
Reductive Denitration of Nitroarenes
Kashihara, Myuto,Yadav, M. Ramu,Nakao, Yoshiaki
supporting information, p. 1655 - 1658 (2018/03/23)
The Pd-catalyzed reductive denitration of nitroarenes has been achieved via a direct cleavage of the C-NO2 bonds. The catalytic conditions reported exhibit a broad substrate scope and good functional-group compatibility. Notably, the use of inexpensive propan-2-ol as a mild reductant suppresses the competitive formation of anilines, which are normally formed by other conventional reductions. Mechanistic studies have revealed that alcohols serve as efficient hydride donors in this reaction, possibly through β-hydride elimination from palladium alkoxides.
Electron Transfer Reactions: KO tBu (but not NaO tBu) Photoreduces Benzophenone under Activation by Visible Light
Nocera, Giuseppe,Young, Allan,Palumbo, Fabrizio,Emery, Katie J.,Coulthard, Graeme,McGuire, Thomas,Tuttle, Tell,Murphy, John A.
, p. 9751 - 9757 (2018/07/21)
Long-standing controversial reports of electron transfer from KOtBu to benzophenone have been investigated and resolved. The mismatch in the oxidation potential of KOtBu (+0.10 V vs SCE in DMF) and the first reduction potential of benzophenone (of many values cited in the literature, the least negative value is -1.31 V vs SCE in DMF), preclude direct electron transfer. Experimental and computational results now establish that a complex is formed between the two reagents, with the potassium ion providing the linkage, which markedly shifts the absorption spectrum to provide a tail in the visible light region. Photoactivation at room temperature by irradiation at defined wavelength (365 or 400 nm), or even by winter daylight, leads to the development of the blue color of the potassium salt of benzophenone ketyl, whereas no reaction is observed when the reaction mixture is maintained in darkness. So, no electron transfer occurs in the ground state. However, when photoexcited, electron transfer occurs within a complex formed from benzophenone and KOtBu. TDDFT studies match experimental findings and also define the electronic transition within the complex as n → π, originating on the butoxide oxygen. Computation and experiment also align in showing that this reaction is selective for KOtBu; no such effect occurs with NaOtBu, providing the first case where such alkali metal ion selectivity is rationalized in detail. Chemical evidence is provided for the photoactivated electron transfer from KOtBu to benzophenone: tert-butoxyl radicals are formed and undergo fragmentation to form (acetone and) methyl radicals, some of which are trapped by benzophenone. Likewise, when KOC(Et)3 is used in place of KOtBu, then ethylation of benzophenone is seen. Further evidence of electron transfer was seen when the reaction was conducted in benzene, in the presence of p-iodotoluene; this triggered BHAS coupling to form 4-methylbiphenyl in 74% yield.
Electrophilic aromatic substitution of arenes with CO2 mediated by R3SiB(C6F5)4
Konno, Megumi,Chiba, Masafumi,Nemoto, Koji,Hattori, Tetsutaro
, p. 913 - 914,2 (2020/08/31)
The FriedelCrafts- type carboxylation of arenes has been achieved by activating CO2 with silylium borates. The reaction exhibits broader substrate applicability than does our previously reported AlX3/R 3SiX-mediated carboxylation.
Direct carboxylation of arenes and halobenzenes with CO2 by the combined use of AlBr3 and R3SiCl
Nemoto, Koji,Yoshida, Hiroki,Egusa, Naoki,Morohashi, Naoya,Hattori, Tetsutaro
experimental part, p. 7855 - 7862 (2011/02/21)
The Lewis acid-mediated direct carboxylation of aromatic compounds with CO2 is efficiently promoted by the addition of silyl chlorides bearing three alkyl and/or aryl substituents in total on the silicon atom. Thus, toluene, xylenes, mesitylene, and some other alkylbenzenes are treated with a 1:1 mixture of AlBr3 and Ph3SiCl in neat substrates under CO2 pressure (3.0 MPa) at room temperature, to give the corresponding carboxylic acids in 60-97% yields, based on AlBr3. Polycyclic arenes, including naphthalene, phenanthrene, and biphenyl, are regioselectively carboxylated in 91-98% yields with the aid of 1 molar equiv of AlBr3 and Ph3SiCl in an appropriate solvent, chosen from benzene, chlorobenzene, and fluorobenzene. These solvents, as well as bromobenzene, resist carboxylation; however, they are also carboxylated in moderate yields when treated with a 1:5 mixture of AlBr3 and iPrSiCl at elevated temperatures. The FT-IR spectrum of a mixture prepared by exposing a suspension of AlBr3 and Ph3SiCl in cyclohexane to CO 2 exhibits an absorption band around 1650 cm-1, assigned to the C=O stretching vibration of a species consisting of CO2, AlBr3, and Ph3SiCl, which suggests that the silyl chlorides activate CO2 in cooperation with AlBr3. 1H NMR analysis of unworked-up reaction mixtures reveals that the products merge as aluminum carboxylates. The mass balance concerning silicon indicates that the silyl chlorides are recycled during the reaction sequence. On the basis of these observations, a feasible mechanism is proposed for the present carboxylation.
o-Benzenedisulfonimide as a reusable Bronsted acid catalyst for Ritter-type reactions
Barbero, Margherita,Bazzi, Stefano,Cadamuro, Silvano,Dughera, Stefano
experimental part, p. 430 - 436 (2009/07/19)
Reactions between various benzyl alcohols or tert-butyl alcohol and nitriles were carried out in the presence of catalytic amounts (usually 10-20 mol-%) of o-benzenedisulfonimide as a Bronsted acid catalyst; the reaction conditions were mild and the yields of amides were good. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
Beneficial effect of TMSCl in the Lewis acid-mediated carboxylation of aromatic compounds with carbon dioxide
Nemoto, Koji,Yoshida, Hiroki,Suzuki, Yutaka,Morohashi, Naoya,Hattori, Tetsutaro
, p. 820 - 821 (2007/10/03)
The Lewis acid-mediated carboxylation of aromatic compounds with CO 2 is significantly promoted by the addition of a large excess of chlorotrimethylsilane (TMSCl) to give arylcarboxylic acids in good to excellent yields. Copyright
A new method for oxidation of various alcohols to the corresponding carbonyl compounds by using n-t-butylbenzenesulfinimidoyl chloride
Matsuo, Jun-Ichi,Iida, Daisuke,Tatani, Kazuya,Mukaiyama, Teruaki
, p. 223 - 234 (2007/10/03)
Various primary and secondary alcohols were smoothly oxidized to the corresponding aldehydes and ketones by using a new oxidizing agent, N-t-butylbenzenesulfinimidoyl chloride (4a), in the coexistence of DBU or zinc oxide. The present oxidation proceeded under mild conditions via five-membered intramolecular proton-transfer of an alkyl arenesulfinimidate intermediate.
Spectroscopic and product studies of the effect of para substituents on the reactivity of triplet bis(2,6-dimethylphenyl)carbenes
Hu, Yingmo,Ishikawa, Yui,Hirai, Katsuyuki,Tomioka, Hideo
, p. 2207 - 2218 (2007/10/03)
A series of diazobis(2,6-dimethylphenyl)methanes (1) bearing eight symmetrical para di-substituents have been prepared and photolyzed to generate the corresponding carbenes (2). Product analysis studies showed that carbenes (2) decay mainly either by dimerization to form tetra(aryl)ethylene (3) or by attack at an o-methyl group to afford 1,2-dihydrobenzocyclobutenes (4) by way of o-quinodimethanes (6) in solution. The zero-field splitting parameters, D and E, were measured in matrices of different viscosities and are analyzed in terms of a sigma-dot (σ.) scale of spin-delocalization substituent constants. Fairly good correlation with σ. was found for the D values of 32 in its minimum energy geometry. Stabilities of 32 were estimated either by measuring the temperature at which the triplet carbene signals disappeared upon thawing the matrix or by analyzing the decay kinetics of 32 in a degassed solution at room temperature. They are examined in terms of the D values in matrix at low temperature and in terms of product distributions in solution at room temperature.
