- Substrate substitution effects in the Fries rearrangement of aryl esters over zeolite catalysts
-
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.
- Bonrath, Werner,Létinois, Ulla,Lin, Ronghe,Medlock, Jonathan,Mitchell, Sharon,Netscher, Thomas,Pérez-Ramírez, Javier,Stemmler, René T.
-
p. 4282 - 4292
(2020/07/30)
-
- Method for preparing 2,3,5-trimethylhydroquinone diester
-
The invention discloses a method for preparing 2,3,5-trimethylhydroquinone diester. The method comprises the following steps: carrying out rearrangement reaction on oxoisophorone and acetic anhydrideunder the catalysis of amino acid and polyethylene glyco
- -
-
Paragraph 0013; 0062-0078
(2020/09/30)
-
- A 2, 3, 5-trimethyl hydroquinone b phytanate method for the preparation of
-
The invention provides a preparation method of 2,3,5-trimethylhydroquinone dialkyl acid ester. The preparation method comprises the following steps: under catalysis of polymer ionic liquid, carrying out rearrangement and acylation reaction on 2,6,6-trimethyl cyclohexyl-2-ene-1, 4-diketone and an acylating agent to prepare the 2,3,5-trimethylhydroquinone dialkyl acid ester. Compared with the traditional acid catalysis, the process has the advantages of easiness in recovering of the catalyst, environmental friendliness, slight corrosion to equipment, high activity, high selectivity and the like.
- -
-
Paragraph 0052; 0053
(2017/05/02)
-
- Efficient access to (All-rac)-α-Tocopherol acetate by a crombie chromene synthesis
-
In contrast to reports in the literature, the pyridine-catalysed condensation of phenolic compounds and conjugated aldehydes to chromenes was found to be applicable to trimethylhydroquinone 2a with the result of complementary convergent approaches to the
- Gembus, Vincent,Sala-Jung, Nathalie,Uguen, Daniel
-
experimental part
p. 843 - 854
(2009/12/25)
-
- Spiro derivatives as lipoxygenase inhibitors
-
The present invention is concerned with certain novel spiro substituted heterocylic ring derivatives. These compounds may be useful in the manufacture of pharmaceutical compositions for treating disorders mediated by lipoxygenases. They may also be useful
- -
-
Page/Page column 74-75
(2008/06/13)
-
- PROCESS FOR THE MANUFACTURE OF TRIMETHYLHYDROQUINE DIALKANOATES
-
The present invention is directed to a process for the manufacture of a 2,3,5-trimethyl-hydroquinone dialkanoate comprising reacting ketoisophorone with an acylating agent in the presence of an indium salt as the catalyst. Preferred are indium(III) salts such as indium trichloride or indium tris (trifluoromethanesulfonate). Further aspects of the present invention are a process for the manufacture of 2,3,5-tri-methylhydroquinone using 2,3,5-trimethylhydroquinone dialkanoate as the starting mate-rial, especially a process for the manufacture of 2,3,5-trimethylhydroquinone by trans-esterification of 2,3,5-trimethylhydroquinone dialkanoate, as well as a process for the manufacture of a-tocopherol and its alkanoates, especially of (all-rac)-a-tocopherol and its acetate, comprising the reaction of ketoisophorone to 2,3,5-trimethylhydroquinone dialka-noate according to the present invention. Furthermore, the present invention also deals with a process for the manufacture of formulations of a-tocopherol and its alkanoates, es-pecially of formulations of (all-rac)-a-tocopherol and its acetate, comprising the reaction of ketoisophorone to 2,3,5-trimethylhydroquinone dialkanoate according to the present invention.
- -
-
Page/Page column 6
(2008/06/13)
-
- PROCESS FOR THE PREPARATION OF 2,3,5-TRIMETHYLHYDROQUINONE DIACYLATES
-
2,3,5-Trimethyl-1,4-hydroquinone diacylates are obtained by reacting 3,5,5-trimethyl-1,4-benzoquinone with an acylating agent in the presence of methane trisulfonic acid as a catalyst.
- -
-
Page/Page column 3-5
(2008/06/13)
-
- Process for producing hydroquinone diester derivative
-
A hydroquinone diester derivative represented by the formula (1): wherein R1and R2are the same or different, each representing an alkyl group, a cycloalkyl group, an aryl group, or a heterocyclic group is crystallized from a reaction
- -
-
-
- Process for preparing trimethylhydroquinone diacetate and trimethylhydroquinone
-
A process for preparing trimethylhydroquinone diacetate, with subsequent hydrolysis to give trimethylhydroquinone, the process including reacting 2,2,6-trimethylcyclohexane-1,4-dione under oxidative conditions, in the presence of a sulfonating agent and a strong acid, and in the presence of an acylating agent.
- -
-
-
- HYDROQUINONE DIESTER DERIVATIVES AND THE METHOD FOR PRODUCING THE SAME
-
A highly pure hydroquinone dietser derivative can be produced from the reaction product of ketoisophorone with an acylating agent in a high yield by a simple and easy operation. In the presence of an acid catalyst, a cyclohex-2-ene-1,4-dione derivative shown by the following formula (3) was allowed to react with an acylating agent (e.g., acetic anhydride), and the reaction product was purified by crystallization to obtain a hydroquinone diester derivative shown by the following formula (1). The compound (1) contains about 0 to 4% by weight of a catechol diester derivative represented by the following formula (2), being highly pure. As a solvent for crystallization, a mixed solvent of an organic carboxylic acid (e.g., acetic acid) corresponding to the acylating agent and water may be used. In the formulae, R1 and R2 each represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group.
- -
-
-
- Process for the preparation of 2,3,5-trimethylhydroquinone diesters
-
Preparation of 2,3,5-trimethylhydroquinone diesters by rearrangement of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (4-oxo-isophorone, ketoisophorone) in the presence of a solid, acid catalyst and an acylating agent, for example carboxylic acid anhydrides or carboxylic acid halides. The 2,3,5-trimethylhydroquinone diester may then optionally be saponified to the free 2,3,5-trimethylhydroquinone, which is a valuable building block in the synthesis of vitamin E.
- -
-
-
- Method for the production of trimethylhydroquinone
-
The invention relates to an improved method for the production of 2,3,5-trimethylhydroquinone by rearranging 4-oxo-isophorone (keto-isophorone, 3,5,5-trimethylcyclohex-2-en[e]-1,4-dione) to a trimethylhydroquinone diester and by its subsequent saponification.
- -
-
-
- Hydroquinone diester derivatives and the method for producing the same
-
A highly pure hydroquinone dietser derivative can be produced from the reaction product of ketoisophorone with an acylating agent in a high yield by a simple and easy operation. In the presence of an acid catalyst, a cyclohex-2-ene-1,4-dione derivative shown by the following formula (3) was allowed to react with an acylating agent (e.g., acetic anhydride), and the reaction product was purified by crystallization to obtain a hydroquinone diester derivative shown by the following formula (1). The compound (1) contains about 0 to 4% by weight of a catechol diester derivative represented by the following formula (2), being highly pure. As a solvent for crystallization, a mixed solvent of an organic carboxylic acid (e.g., acetic acid) corresponding to the acylating agent and water may be used. In the formulae, R1and R2each represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group.
- -
-
-
- Process for the production of trimethylhydroquinone diesters and of trimethylhydroquinone
-
An improved process for the production of 2,3,5-trimethylhydroquinone by rearrangement of 4-oxoisophorone (ketoisophorone, 3,5,5-trimethyl-2-cyclohexen-1,4-dione) to yield a trimethylhydroquinone diester and the subsequent saponification thereof. Trimethylhydroquinone is in turn an important starting material for the production of vitamin E.
- -
-
-
- Method for producing trimethylhydroquinone diester
-
This method provides trimethylhydroquinone diester by using a recyclable catalyst which shows high activity and operability in the reaction, while reducing the risk of corrosion of the reactor. The method for the production of 2,5,6-trimethylhydroquinone diester comprises reacting 2,6,6-trimethylcyclohexe-2-en-1,4-dione with an acylating agent in the presence of a solid catalyst. The acylating agent includes a C2-4 carboxylic acid anhydride (e.g. acetic anhydride) and a C2-4 carboxylic acid halide (e.g. acetyl chloride). The solid catalyst includes a solid acid catalyst (e.g. strongly or super-strongly acidic ion exchange resin, compound oxide, zeolite, heteropoly acid).
- -
-
-
- Tocopherol derivatives useful in the synthesis of vitamin E and their preparation
-
Tocopherol derivatives of the formula: STR1 in which X and X1, which may be identical or different, each represent hydrogen or chlorine and their acetates are useful in the synthesis of vitamin E.
- -
-
-
- REACTION OF 1,2,4-TRIMETHYLBENZENE WITH PERACETIC ACID
-
The oxidation of 1,2,4-trimethylbenzene with peracetic acid leads to the formation of trimethylphenols and hydroquinones, which undergo transformations to the corresponding benzoquinones and products from oxidative cleavage of the ring.The controlling stage of the process is the electrophilic hydroxylation of 1,2,4-trimethylbenzene.
- Kharchuk, V. G.,Kolenko, I. P.,Petrov, L. A.,Gus'kova, L. M.
-
p. 2071 - 2078
(2007/10/02)
-