1341-82-8Relevant articles and documents
NEW METHOD FOR PREPARING 2-TERT-BUTYL-4-METHOXYPHENOL AND NEW CRYSTAL FORM THEREOF
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Paragraph 0041; 0039; 0040, (2021/10/15)
The present invention relates to a stable crystal form, i.e. form A, of 2-tert-butyl-4-methoxyphenol, and to a new preparation method for the 2-tert-butyl-4-methoxyphenol; and the use of the 2-tert-butyl-4-methoxyphenol and the stable crystal form thereof, i.e. form A, in preparing antitumor drugs or immunomodulator drugs. The stable crystal form, i.e. form A, as expressed by a powder X-ray diffraction pattern in an angle of 2θ, using Cu-Kα radiation, has at least 3 absorption peaks selected from the following positions: 6.27±0.10, 6.94±0.10, 12.27±0.10, 13.36±0.10, 14.01±0.10, 14.79±0.10, 15.31±0.10, 17.05±0.10, 18.30±0.10, 19.00±0.10, 20.47±0.10, 20.98±0.10, 22.37±0.10, 23.68±0.10, 24.55±0.10, 25.37±0.10, 30.83±0.10, 33.12±0.10, 40.50±0.10, 42.81±0.10.
Hydrolysis stability of bidentate phosphites utilized as modifying ligands in the Rh-catalyzed n-regioselective hydroformylation of olefins
Zhang, Baoxin,Jiao, Haijun,Michalik, Dirk,Klo?, Svenja,Deter, Lisa Marie,Selent, Detlef,Spannenberg, Anke,Franke, Robert,B?rner, Armin
, p. 7554 - 7565 (2018/05/23)
The stability of ligands and catalysts is an almost neglected issue in homogeneous catalysis, but it is crucial for successful application of this methodology in technical scale. We have studied the effect of water on phosphites, which are the most applied cocatalysts in the n-regioselective homogeneous Rh-catalyzed hydroformylation of olefins. The stability of the bidentate nonsymmetrical diphosphite L1, as well as its two monophosphite constituents L2 and L3, toward hydrolysis was investigated by means of in situ NMR spectroscopy under similar conditions as applied in industry. Hydrolysis pathways, intermediates, and kinetics were clarified. DFT calculations were used to support the experimentally found data. The acylphosphite unit L2, which reacts with water in an unselective manner, was proven to be much less stable than the phenolphosphite L3. The stability of the bidentate ligand L1 can be therefore mainly attributed to its phenolphosphite moiety. With an excess of water, the hydrolysis of L1 and L2 as well as their Rh-complexes is first-order with respect to the phosphite. Surprisingly, coordination to Rh significantly stabilizes the monodentate ligand L2, while in strong contrast, the bidentate ligand L1 decomposes faster in the Rh complex. NMR spectroscopy provided evidence for the existence of species from decomposition of phosphites, which can likewise coordinate as ligands to the metal. Electron-withdrawing groups in the periphery of the acylphosphite moiety decrease the stability of L1, whereas 3,5-disubstituted salicylic acid derivatives with bulky groups showed superior stability. These modifications of L1 also give rise to different catalytic performances in the n-regioselective hydroformylation of n-octenes and 2-pentene, from which the 3,5-di-t-butyl-substituted ligand offered a higher n-regioselectivity accompanied by a lowering of the reaction rate in comparison to the parent ligand L1.
Photochemistry of aryl tert-butyl ethers in methanol: The effect of substituents on an excited state cleavage reaction
DeCosta,Bennett,Pincock,Pincock,Stefanova
, p. 4162 - 4168 (2007/10/03)
The photolysis of a set of 10 substituted aryl tert-butyl ethers, 8a-j, in methanol gave, as the major product, the corresponding phenol along with tert-butyl-substituted phenols resulting from photo-Fries reaction. The corresponding 4-cyanophenyl 1-adamantyl ether, 9, also gave 1-meth-oxyadamantane 16 (16%), indicating that, at least for this ether, some of the products were ion-derived. Quenching studies with 2,3-dimethylbutadiene for the tert-butyl ethers indicated that these reactions were occurring from the singlet excited state. Rate constants for the reaction, obtained from quantum yields and singlet lifetimes, were found to correlate reasonably well with σhv values, ρ = -0.77 (r = 0.975), a result that is unexpected for a reaction where the polarity of the bond breaking in the transition state is expected to be -O(δ-)···C(δ+).
