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.
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.
