(19) TZZ ¥Z_T (11) EP 2 655 308 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C07C 45/45 (2006.01) C07C 49/84 (2006.01) 07.03.2018 Bulletin 2018/10 (86) International application number: (21) Application number: 11804542.6 PCT/EP2011/073172 (22) Date of filing: 19.12.2011 (87) International publication number: WO 2012/084770 (28.06.2012 Gazette 2012/26) (54) PROCESS FOR THE MANUFACTURE OF DIBENZOYLMETHANE DERIVATIVES VERFAHREN ZUR HERSTELLUNG VON DIBENZOYLMETHANDERIVATEN PROCÉDÉ DE PRODUCTION DE DÉRIVÉS DE DIBENZOYLMÉTHANE (84) Designated Contracting States: • NANDURKAR NITIN S ET AL: "Synthesis of AL AT BE BG CH CY CZ DE DK EE ES FI FR GB sterically hindered 1,3-diketones", SYNTHETIC GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO COMMUNICATIONS, TAYLOR & FRANCIS PL PT RO RS SE SI SK SM TR GROUP, PHILADELPHIA, PA, vol. 37, no. 23, 1 January 2007 (2007-01-01), pages 4111-4115, (30) Priority: 20.12.2010 EP 10195971 XP009144707, ISSN: 0039-7911, DOI: DOI:10.1080/00397910701572803 (43) Date of publication of application: • GUOQING ZHANG ET AL: "Polymorphism and 30.10.2013 Bulletin 2013/44 Reversible Mechanochromic Luminescence for Solid-State Difluoroboron Avobenzone", (73) Proprietor: DSM IP Assets B.V. JOURNAL OF THE AMERICAN CHEMICAL 6411 TE Heerlen (NL) SOCIETY, AMERICAN CHEMICAL SOCIETY, US, vol. 132, 1 January 2010 (2010-01-01), pages (72) Inventor: WEHRLI, Christof 2160-2162, XP007917212, ISSN: 0002-7863, DOI: CH-4002 Basel (CH) DOI:10.1021/JA9097719 [retrieved on 2010-01-28] • FRANEK W: "New Dithio-bis-(diaroylmethanes) (74) Representative: Berg, Katja et al and Acetyl Diaroylchloromethyl Disulfides: DSM Nutritional Products AG Attractive Synthons and Precursors for the Wurmisweg 576 Liberation of Highly Reactive Dithiiranes or CH-4303 Kaiseraugst (CH) Thiosulfines", MONATSHEFTE FUR CHEMIE, SPRINGER VERLAG WIEN, AT, vol. 127, 1 (56) References cited: January 1996 (1996-01-01), pages 895-907, DE-A1- 4 427 512 US-A- 5 344 992 XP007917213, ISSN: 0026-9247 US-A1- 2009 246 156 US-B1- 6 410 795 • ISHIDA J ET AL: "Antitumor Agents. Part 214: Synthesis and Evaluation of Curcumin Analogues as Cytotoxic Agents", BIOORGANIC &MEDICINAL CHEMISTRY, PERGAMON, GB, vol. 10,1 January 2002 (2002-01-01), pages 3481-3487, XP002536790, ISSN: 0968-0896, DOI: DOI:10.1016/S0968-0896(02)00249-3 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 2 655 308 B1 Printed by Jouve, 75001 PARIS (FR) EP 2 655 308 B1 Description [0001] The invention relates to an improved process for the manufacture of substituted dibenzoylmethane derivatives. This novel economical process provides products in high purity and yields and results in shorter reaction times. 5 [0002] Substituted dibenzoylmethane derivatives are highly effective UVA-absorbers which are, for example, used as light stabilizers in plastics or as light screening agents in cosmetic products. Customary dibenzoylmethane derivatives are, for example, Eusolex® 8020 [INCI Name: Isopropyldibenzoylmethane; CAS No.: 63250-25-9] or PARSOL® 1789 [INCI Name: butyl methoxydibenzoylmethane; 4-tert-butyl-4’-methoxydibenzoylmethane, CAS No.: 70356-09-1]. [0003] Substituted dibenzoylmethane derivatives may be prepared by Aldol condensation of a ketone with an ester 10 in the presence of a strong base such as e.g. disclosed in DE 2945125 or US 6,278,025. Suitable bases cited by the references are sodium hydride, sodium amide or alkali or earth alkali metal alkoxides such as in particular sodium methylate. [0004] US6410795 discloses the formation of 1,3-diketone by condensation of a carboxylic acid ester and a ketone in the presence of an alkali metal alcoholate and an aromatic hydrocarbon. DE4427512 discloses a process for the 15 preparation of linear 1,3-diketones by Claisen condensation and their use as polymer stabilizers. [0005] US5344992 discloses a process for the preparation of linear 1,3-diketones comprising the Claisen condensation of Me ketone derivatives with esters or lactones in the presence of an alkali or alkali earth metal hydride or alkoxide in a DMSO-containing solvent mixture. [0006] Nandurkar et al (Synthetic Communications (2007), 37(13), 4111-15) discloses a method for the synthesis of 20 sterically hindered aliphatic/ aromatic 1,3-diketones via coupling of ketones with esters using potassium tert-butoxide. [0007] Guoqing et al (Journal of the American Chemical Society (2010), 132(7), 2160-2) discloses difluoroboron avobenzone, a simple boron complex of a commercial sunscreen. [0008] Franek et al (Monatshefte fuer Chemie (1996), 127(8/9), 895-907) discloses a procedure to prepare diaroyl- methanes from the respective carboxylic acid esters and methyl ketones. 25 [0009] Ishida et al (Bioorg. & Med. Chem, (2002), vol. 10, 3481-87) discloses the preparation of some curcumin analogues as well as their use as antitumor agents [0010] US2009246156 discloses avobenzone in sunscreen compositions, but no process for its preparation. [0011] Because of the continuously increasing demand for dibenzoylmethane based light screening agents the object of the present invention was to provide a process for the preparation of substituted dibenzoylmethane derivatives which 30 is easy to carry out and affords economic advantages as a result of high yields. Furthermore, the process yields purer products as the hardly removable symmetric by-products are formed to a lesser extend. This is particularly important because minor impurities tend to impart a color to the product which is unwanted for use in cosmetic formulations. [0012] Surprisingly, it has been found that the use of potassium alcoholate as base delivers higher yields and less side products compared to the use of other bases. Furthermore, the intermediate potassium salt formed during the 35 reaction does not crystallize in the reaction mixture, thus facilitating industrial handling. Additionally, the reaction times can be reduced by the use of a potassium alcoholate as base. [0013] Thus, the invention relates to a process for the preparation of substituted dibenzoylmethane derivatives of formula (I) 40 45 wherein 50 1 2 R and R are independently selected from the group consisting of hydrogen, C 1 to C12 alkyl, C1 to C12 alkoxy, C3 to C12 alkenyloxy and C2 to C12 alkenyl; characterized in that said process comprises the step of forming the potassium salt of (I) by condensing a ketone of formula (II) with an ester of formula (III) in the presence of a potassium alcoholate (IV) (condensation step) 55 2 EP 2 655 308 B1 5 wherein 10 R1 and R2 are as defined above R3 is hydrogen; 4 R is C1 to C12 alkyl and 5 1 2 R is C1 to C8 alkyl. with the proviso that at least one of R and R is not hydrogen and 15 with the proviso that the potassium alkoxide is potassium methylate, potassium-isopropylate and/ or potassium tert.-butylate, the reaction temperature is selected in the range of 80-150°C, the reaction is carried out in an inert solvent selected from the group of aromatic or hydrocarbon solvents as well as mixtures thereof and 20 wherein the alcohols R4 OH and R5 OH are removed continuously as formed. In another embodiment, the invention relates to a process for the preparation of substituted dibenzoylmethane derivatives of formula (I) 1 2 wherein R and R are independently selected from the group consisting of hydrogen, C1 to C12 alkyl, C1 to 1 2 C12 alkoxy, C3 to C12 alkenyloxy and C2 to C12 alkenyl with the proviso that at least one of R and R is not hydrogen and with the proviso that the potassium alcoholate is derived from an alcohol R 5-OH having a boiling 25 point below 100°C. [0014] Ina particularembodiment, theinvention relates to a processfor the preparation of dibenzoylmethanederivatives 1 2 of formula (I) wherein R and R are independently selected from the group consisting of hydrogen, C 1 to C12 alkyl and 1 2 C1 to C12 alkoxy. More in particular R is a C1 to C8 alkoxy radical and R is a C1 to C8 alkyl radical, most in particular 30 1 R is a C 1 to C 4 alkoxy radical such as methoxy, ethoxy, isopropoxy, n-propoxy, 1-methylpropoxy, t-butoxy and n-butoxy 2 and R is a C1 to C4 alkyl radical such as methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl and 1,1-dimethylethyl. Most in particular, the invention relates to a process for the preparation of butyl methoxydiben- zoylmethane (i.e. R1 is methoxy and R2 is 1,1-dimethylethyl). [0015] Examples of alkyl, respectively alkenyl radicals are branched or unbranched alkyl, respectively alkenyl chains 35 such as methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl-, 2-methylpropyl, 1,1-dimethylethyl, n-pentyl, 1- methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethyl- propyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimeth- ylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2- trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, 2-ethylhexyl, n-octyl, n-nonyl, n-decyl, n-unde- 40 cyl, n-dodecyl, ethenyl, 2-propenyl and 3-butenyl. [0016] Examples of alkoxy, respectively alkenyloxy radicals are e.g.