697-82-5Relevant articles and documents
REARRANGEMENT OF DIMETHYLPHENYLACYLATES USING ZEOLITES
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Page/Page column 9-10; 14, (2021/08/14)
The present invention relates to a Fries rearrangement of specific dimethylphenylacylates to form the desired respective hydroxyaryl ketones having two methyl groups bound to the aromatic ring. It has been found that the process is surprisingly very specific in view of the number and position of the methyl group(s) bound to the aromatic ring.
Substrate substitution effects in the Fries rearrangement of aryl esters over zeolite catalysts
Bonrath, Werner,Létinois, Ulla,Lin, Ronghe,Medlock, Jonathan,Mitchell, Sharon,Netscher, Thomas,Pérez-Ramírez, Javier,Stemmler, René T.
, p. 4282 - 4292 (2020/07/30)
The catalytic transformation of aryl esters to hydroxyacetophenones via Fries rearrangement over solid acids is of interest to avoid the use of corrosive and toxic Lewis and Br?nsted acids traditionally applied. Microporous zeolites are known to catalyze the reaction of simple substrates such as phenyl acetate, but their application to substituted derivatives has received limited attention. To refine structure-activity relationships, here we examine the impact of various parameters including the solvent polarity, water content, acidic properties, and framework type on the reaction scheme in the Fries rearrangement of p-tolyl acetate over common solid acids. The results confirm the importance of providing a high concentration of accessible Br?nsted acid sites, with beta zeolites exhibiting the best performance. Extension of the substrate scope by substituting methyl groups in multiple positions identifies a framework-dependent effect on the rearrangement chemistry and highlights the potential for the transformation of dimethylphenyl acetates. Kinetic studies show that the major competitive path of cleavage of the ester C-O bond usually occurs in parallel to the Fries rearrangement. The possibility of sequentially acylating the resulting phenol depends on the substrate and reaction conditions.
An Enzymatic Route to α-Tocopherol Synthons: Aromatic Hydroxylation of Pseudocumene and Mesitylene with P450 BM3
Dennig, Alexander,Weingartner, Alexandra Maria,Kardashliev, Tsvetan,Müller, Christina Andrea,Tassano, Erika,Schürmann, Martin,Ruff, Anna Jo?lle,Schwaneberg, Ulrich
, p. 17981 - 17991 (2017/11/29)
Aromatic hydroxylation of pseudocumene (1 a) and mesitylene (1 b) with P450 BM3 yields key phenolic building blocks for α-tocopherol synthesis. The P450 BM3 wild-type (WT) catalyzed selective aromatic hydroxylation of 1 b (94 %), whereas 1 a was hydroxylated to a large extent on benzylic positions (46–64 %). Site-saturation mutagenesis generated a new P450 BM3 mutant, herein named “variant M3” (R47S, Y51W, A330F, I401M), with significantly increased coupling efficiency (3- to 8-fold) and activity (75- to 230-fold) for the conversion of 1 a and 1 b. Additional π–π interactions introduced by mutation A330F improved not only productivity and coupling efficiency, but also selectivity toward aromatic hydroxylation of 1 a (61 to 75 %). Under continuous nicotinamide adenine dinucleotide phosphate recycling, the novel P450 BM3 variant M3 was able to produce the key tocopherol precursor trimethylhydroquinone (3 a; 35 % selectivity; 0.18 mg mL?1) directly from 1 a. In the case of 1 b, overoxidation leads to dearomatization and the formation of a valuable p-quinol synthon that can directly serve as an educt for the synthesis of 3 a. Detailed product pattern analysis, substrate docking, and mechanistic considerations support the hypothesis that 1 a binds in an inverted orientation in the active site of P450 BM3 WT, relative to P450 BM3 variant M3, to allow this change in chemoselectivity. This study provides an enzymatic route to key phenolic synthons for α-tocopherols and the first catalytic and mechanistic insights into direct aromatic hydroxylation and dearomatization of trimethylbenzenes with O2.
Construction of Acid–Base Synergetic Sites on Mg-bearing BEA Zeolites Triggers the Unexpected Low-Temperature Alkylation of Phenol
Xie, Jingyan,Zhuang, Wenxia,Zhang, Wei,Yan, Ning,Zhou, Yu,Wang, Jun
, p. 1076 - 1083 (2017/03/27)
Novel Mg-bearing BEA zeolites are synthesized to simultaneously endow significantly enhanced basicity without compromising acidity over the zeolite framework. Serving as efficient solid acid–base bifunctional catalysts, they achieve the liquid-phase selective methylation of phenol with methanol to produce o- and p-cresol (o/p=2) under mild conditions. The method is readily extendable to the alkylation of phenols with various alcohols. Stereo- and regioselectivity (>95 % for p-product) was attained on the alkylation of phenol with bulky tert-butyl alcohol, rendering the first acid–base cooperative shape-selective catalysis relying on the basicity of zeolites. A preliminary mechanistic analysis reveals that the remarkable activity and shape-selectivity come from the superior special acidic–basic synergetic catalytic sites on the uniform microporous channels of the BEA zeolite.
Selective oxidation of pseudocumene and 2-methylnaphthalene with aqueous hydrogen peroxide catalyzed by γ-Keggin divanadium-substituted polyoxotungstate
Zalomaeva, Olga V.,Evtushok, Vasiliy Yu.,Maksimov, Gennadii M.,Kholdeeva, Oxana A.
, p. 210 - 216 (2015/09/01)
The catalytic performance of a γ-Keggin divanadium-substituted phosphotungstate, (Bu4N)4[γ-PW10O38V2(μ-O)(μ-OH)], has been evaluated in the selective oxidation of 1,2,4-trimethylbenzene (pseudocumene, PC) and 2-methylnaphthalene with the green oxidant, 35% aqueous hydrogen peroxide. Under conditions of H2O2 deficiency ([PC]/[H2O2] = 17-22), PC oxidation proceeded with unusually high chemo- and regioselectivity, producing exclusively 2,4,5-trimethylphenol (2,4,5-TMP) and 2,3,5-TMP in a molar ratio of 7.3/1 and a yield of 73% based on the oxidant. Isomeric 2,3,6-trimethylphenol was found in trace amounts. Under conditions of H2O2 excess ([H2O2]/[PC] = 8), 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate) formed with 41% selectivity at 41% substrate conversion. Atypical regioselectivity was also found in the oxidation of 2-methylnaphthalene which gave predominantly 6-methyl-1,4-naphthoquinone (6-MNQ) rather than isomeric 2-MNQ. The ratio between the isomers could be altered by varying the catalyst and oxidant amounts.
Selective oxidative homo-and cross-coupling of phenols with aerobic catalysts
Lee, Young Eun,Cao, Trung,Torruellas, Carilyn,Kozlowski, Marisa C.
supporting information, p. 6782 - 6785 (2014/06/09)
Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described. In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo-and regioselectivity.
A total synthesis of yellowish aphid pigment furanaphin through fries rearrangement assisted by boron trifluoride-acetic acid complex
Nishimura, Taichi,Iwata, Takeki,Maegawa, Hironori,Nishii, Takeshi,Matsugasako, Masami,Kaku, Hiroto,Horikawa, Mitsuyo,Inai, Makoto,Tsunoda, Tetsuto
scheme or table, p. 1789 - 1792 (2012/08/29)
The yellowish aphid pigment furanaphin, isolated from Aphis spiraecola and possessing cytotoxicity against HL-60 (human promyelocytic leukemia-60) cells, was synthesized by utilizing the Fries rearrangement assisted with a BFmiddot;2AcOH complex as a key step. It was confirmed that the complex effectively mediated the reaction even though the compounds had an electron-withdrawing substituent.
The use of Hagemann's Esters to prepare highly functionalized phenols and benzenes
Majetich, George,Allen, Scott
, p. 104 - 124 (2012/11/07)
Hagemann's esters can be converted into highly functionalized phenols or arenes. The systematic functionalization of Hagemann's ester derivatives permits the preparation of tri-and tetraalkyl-substituted phenols or tetra-, penta-, and hexaalkyl-substituted benzenes. Kotnis's aromatization procedure was found to be solvent dependent, and Suzuki couplings were found to be sensitive to steric hindrance. Wittig olefination and ortho-Claisen reactions were reliable means to introduce alkyl substituents at C-4 and/or C-5 positions, respectively. The acid-promoted dehydration of tertiary alcohol 46 to produce enone 47, followed by its selective alkylation (cf. 48) is new. ARKAT USA, Inc.
Catalytic activity of a mordenite catalyst in alkylation of xylenols with methanol
Agaev,Madatzade
, p. 683 - 684 (2007/10/03)
The catalytic activity of a palladium-containing mordenite catalyst in alkylation of 2,6-, 2,4-, 2,5-, 2,3-, 3,4-, and 3,5-xylenols with methanol was studied. The main and by-products of catalysis and the activity of the catalyst in synthesis of individual trimethylphenols were determined.
Metal ion promoted transesterifications of carboxylate esters. A structure/activity study of the efficacy of Zn2+ and La3+ to catalyze the methanolysis of some aryl and aliphatic esters
Neverov, Alexei A.,Sunderland,Brown, R. Stan
, p. 65 - 72 (2007/10/03)
The methanolysis of various aryl and aliphatic carboxylate esters promoted by methoxide, 1,5,9-triazacyclododecane: Zn2+(-OCH 3) and La3+(-OCH3), were studied and the derived rate constants (kOCH3, kcat 3:Zn(OCH3) and kcatLa(OCH3)) correlated in various ways. The metal ion catalyzed reactions are very much faster than the background reactions in some cases reaching up to 7 × 106-fold acceleration when present at concentrations of 5 mmol dm-3. The data for both metals exhibit non-linear Bronsted correlations with the pK a of the leaving group which are analyzed in terms of a change in rate limiting step from formation to breakdown of a metal-coordinated tetrahedral intermediate as the pKa increases above values of ～14.7. Plots of the log kOCH3 reaction vs. the log k cat, values for each metal ion indicate low sensitivity for aryl esters and a higher sensitivity for the aliphatic esters. A mechanistic rationale for the observations is presented.
