Europaisches Patentamt European Patent Office © Publication number: 0 468 477 A1 Office europeen des brevets EUROPEAN PATENT APPLICATION © Application number: 91112421.2421.2 © int. Ci.5; C07C 37/60, C07C 39/08 @ Date of filing: 24.07.91 ® Priority: 26.07.90 JP 198745/90 © Applicant: DAINIPPON INK AND CHEMICALS, INC. @ Date of publication of application: 35-58, Sakashita 3-chome 29.01.92 Bulletin 92/05 Itabashi-ku Tokyo(JP) © Designated Contracting States: @ Inventor: Takahashi, Katsuji DE FR GB IT 4-3-6, Chishirodai Minami Chiba-shi, Chiba(JP) Inventor: Uohama, Misao 1550-2, Mutsuzaki Sakura-shi, Chiba(JP) Inventor: Akiyama, Takayuki 1550-1, Mutsuzaki Sakura-shi, Chiba(JP) © Representative: Hansen, Bernd, Dr. Dipl.-Chem. et al Hoffmann, Eitle & Partner Patent- und Rechtsanwalte Arabellastrasse 4 Postfach 81 04 20 W-8000 Munchen 81 (DE) © Process for producing dihydric phenols. © A process for producing dihydric phenols is disclosed. The process comprises reacting a phenol with a ketone peroxide or a combination of a ketone and hydrogen peroxide in the presence of a compound having at least one P-S bond. Dihydric phenols can be produced in high yield without requiring neutralization after the reaction. 00 CO Rank Xerox (UK) Business Services EP 0 468 477 A1 FIELD OF THE INVENTION This invention relates to a process for producing dihydric phenols, e.g., catechol and hydroquinone, which are useful as starting materials for pharmaceuticals, agricultural chemicals, perfumes, and the like. 5 BACKGROUND OF THE INVENTION Processes for producing dihydric phenols, e.g., catechol and hydroquinone, by hydroxylation of phenols include so-called ketone peroxide processes comprising reacting a phenol with a ketone peroxide in the io presence of a sulfuric acid catalyst which are known to attain the highest yield (see U.S. Patents 4,078,006). Any of the known ketone peroxide processes, however, is still unsatisfactory in view of the yield and ease of isolation of the product. For example, use a large quantity of a sulfate as a catalyst in these processes not only makes it difficult to separate the catalyst from the product but requires a neutralization step. If the amount of the sulfate to be used is reduced, the yield of the product decreases. When in using 75 sulfuric acid as a catalyst, the yield reached is low regardless of its amount, and a neutralization step is still needed. SUMMARY OF THE INVENTION 20 An object of the present invention is to provide a process for producing dihydric phenols in high yield, which requires no neutralization after the reaction thereby allowing to effect reductions of the size of a reaction apparatus and the cost of production. The inventors have conducted extensive investigations in the light of the above-mentioned present circumstances and found as a result that the above object of the present invention is accomplished by 25 reacting a phenol with a ketone peroxide or a combination of a ketone and hydrogen peroxide in the presence of a compound having at least one P-S bond and thus reached the present invention. The present invention relates to a process for producing a dihydric phenol comprising reacting a phenol with a ketone peroxide or a combination of a ketone and hydrogen peroxide in the presence of a compound having at least one P-S bond. 30 DETAILED DESCRIPTION OF THE INVENTION For the sake of convenience of explanation, the process according to the present invention is divided into two modes according to the type of the oxidizing agent for hydroxylation of the phenolic nucleus:-(1) a 35 process of using a ketone and hydrogen peroxide, and (2) a process of using a ketone peroxide. Process (1) can be carried out according to either (1-a) a mode in which a ketone and hydrogen peroxide are previously mixed together and then added to a mixture of a phenol and a compound having at least one P-S bond to conduct a reaction for a period of from 5 minutes to 3 hours, followed by isolation or (1-b) a mode in which hydrogen peroxide is added to a mixture of a phenol, a ketone, and a compound 40 having at least one P-S bond to conduct a reaction for a period of from 5 minutes to 3 hours, followed by isolation. In either of modes (1-a) and (1-b), while the addition operation may be performed continuously or intermittently, it is recommended to make the addition all at once in the shortest possible time for obtaining a high yield. Process (2) can be carried out by adding dropwise a ketone peroxide to a mixed solution of a phenol 45 and a compound having at least one P-S bond, allowing the mixture to react for a period of form 5 minutes to 3 hours, and isolating the product. In process (2), too, the addition is preferably done through single operation in the shortest possible time. The compound having at least one P-S bond which can be used in the present invention include those having at least one P-S single bond and those having at least one P-»S coordinate bond, e.g., phosphine 50 sulfides and P+Sio- The latter compounds are preferred from the viewpoint of yield. Specific examples of the compounds having at least one P-S single bond include di(arylthio)phosphinic acids, e.g., di(phenylthio)phosphinic acid aniline salt; di(alkylthio)phosphinic acids, e.g., di(n-butylthio)- phosphinic acid aniline salt; and trialkyl trithiophosphites, e.g., trilauryl trithiophosphite. Specific examples of the phosphine sulfides include dithiophosphoric acid esters, e.g., diethyl 55 dithiophosphate, dithiophosphoric acid 0,0-diethyl ester, tri-n-butyl tetrathiophosphate, thiophosphonic acid O-phenyl-O.O-diethyl ester, and diethoxythiophosphonic acid; dithiadiphosphethane disulfides, e.g., 2,4-bis- (4-methoxyphenyl)-1 ,3-dithia-2,4-diphosphethane-2,4-disulfide, and 1 ,3-dithia-2,4-[2,4-bis(2,6-dioxo-4,4- dimethyl)]dicyclophosphethane; dithiadiphosphethane trisulfides, e.g., tetra(n-butoxy)thiophosphoryl trisul- 2 EP 0 468 477 A1 fide, tetra(2-ethylhexanoyl)thiophosphoryl trisulfide, and di(n-butoxy-2-ethylhexanoyl)thiophosphoryl trisul- fide; triphenylphosphine sulfide, tetramethyldiphosphine disulfide, etc. The P-»S bond is sometimes repre- sented by a P = S double bond. P4S10 is a compound called tetraphosphorus decasulfide or phosphorus pentasulfide. 5 The amount of the compound having at least one P-S bond to be used is not particularly critical. A suitable amount for obtaining a sufficient reaction rate usually ranges from 0.0001 to 1 part, and preferably from 0.001 to 0.01 part, by weight per 100 parts by weight of the phenol to be used for the reaction. The phenol which can be used in the present invention is not particularly limited and includes, for example, phenol, anisole, o-cresol, p-cresol, o-chlorophenol, p-chlorophenol, o-bromophenol, p- 10 bromophenol, o-methoxyphenol, p-methoxyphenol, o-ethylphenol, p-ethylphenol, o-(isopropyl)phenol, p- (isopropyl)phenol, o-(n-propyl)phenol, p-(n-propyl)phenol, o-(n-butyl)phenol, p-(n-butyl)phenol, o-(isobutyl)- phenol, p-(isobutyl)phenol, o-(t-butyl)phenol, and p-(t-butyl)phenol. The ketone to be used together with hydrogen peroxide according to process (1) is not particularly limited and includes compounds represented by formula (I): 15 0 » R1-C-R2 (I) 20 wherein R1 and R2, which may be the same or different, each represent an alkyl group having up to 12 carbon atoms or an aryl group, or they are taken together to form a ring. Specific examples of the ketone are methyl isobutyl ketone, methyl ethyl ketone, acetone, cyclohex- 25 anone, and acetophenone, with methyl isobutyl ketone being preferred. Hydrogen peroxide may be anhydrous or aqueous but is preferably used as aqueous hydrogen peroxide for its ease of handling. The concentration of aqueous hydrogen peroxide, while not being limited, is preferably as high as possible, and particularly 60% by weight or higher. The amount of the ketone to be used is not particularly limited but preferably ranges from 0.01 to 10 30 mols per mol of hydrogen peroxide. The ketone peroxide which can be used in process (2) is not particularly limited and includes, for example, compounds represented by formula (II): HO OOH \ / R3 - C - RA (II) 40 wherein R3 and R+, which may be the same or different, each represent an alkyl group having up to 12 carbon atoms or an aryl group, or they are taken together to form a ring. Specific examples of the ketone peroxide include methyl isobutyl ketone peroxide, diisobutyl ketone peroxide, acetone peroxide, and acetophenone peroxide, with methyl isobutyl ketone peroxide being 45 preferred. The amount of the hydrogen peroxide or ketone peroxide to be used is not particularly critical but preferably ranges from 0.01 to 1 .0 mol per mol of the phenol from the viewpoint of yield and inhibition of side reactions such as oxidation of the dihydric phenol produced. The reaction temperature preferably ranges from 50 to 200° C, though varying depending on the activity 50 of the compound having at least one P-S bond and the reactivity of the phenol to be hydroxylated. To ensure a sufficient reaction rate, a range of from 80 to 150°C is more preferred. The reaction temperature may be adjusted by increasing or decreasing the amount of the catalyst to be used. The reaction time preferably ranges from 5 minutes to 3 hours, and more preferably ranges from 15 minutes to 60 minutes. 55 The reaction may be performed without a solvent, or, if desired, an inert solvent may be employed.