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Ep 1 854 797 A1 (19) & (11) EP 1 854 797 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 14.11.2007 Bulletin 2007/46 C07D 487/16 (2006.01) (21) Application number: 06384011.0 (22) Date of filing: 02.05.2006 (84) Designated Contracting States: • Jiménez Alonso, Oscar AT BE BG CH CY CZ DE DK EE ES FI FR GB GR 08006 Barcelona (ES) HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI •Holenz, Jörg SK TR Lab. del Dr. Esteve, S.A. Designated Extension States: 08041 Barcelona (ES) AL BA HR MK YU • Corbera Arjona, Jordi Lab. del Dr. Esteve, S.A. (71) Applicant: ISDIN, S.A. 08041 Barcelona (ES) 08006 Barcelona (ES) • Payella, David 08030 Barcelona (ES) (72) Inventors: • Pelejero, Carles • Schwarz, Marcus 08030 Barcelona (ES) Leipzigerstr. 29 • Trullas, Carles Ramón 09596 Freiberg (ES) 08030 Barcelona (ES) • Buschmann, Helmut H. Lab. del Dr. Esteve, S.A. (74) Representative: Barlocci, Anna et al 08041 Barcelona (ES) ZBM Patents • Kroke, Edwin Zea, Barlocci & Markvardsen Leipziger Str. 29, 09596 Freiberg (DE) C/ Balmes, 114 - 4T 08008 Barcelona (ES) (54) Process for preparing cyameluric chloride (57) The present invention concerns an improved process for obtaining larger quantities (several 10 grams up to kilograms) of pure cyameluric chloride (I) by chlo- rination of cyameluric acid (C6N7(OH)3) or its alkaline salts followed by fractioned vacuum sublimation. EP 1 854 797 A1 Printed by Jouve, 75001 PARIS (FR) 1 EP 1 854 797 A1 2 Description tives for rocket propellants (see US 3,202,659), stabiliz- ers for photographic emulsions (see US 2,704,716 and FIELD OF THE INVENTION US 2,801,172), dyes (see DE 1,102,321), graphitic C3N4 structures as a suitable precursors of superhard C3N4 [0001] The present invention concerns an improved 5 phases (see Kroke,E.; New J. Chem.; (2002); 26; process for obtaining larger quantities (several 10 grams 508-512). It also is an intermediate for the preparation of up to kilograms) of pure cyameluric chloride (I) by chlo- several variously usable heptazine derivatives that has rination of cyameluric acid (C6N7(OH)3) or its alkaline been pointed out elsewhere (see Pauling,L.; Proc. Nat. salts followed by fractioned vacuum sublimation. 2,5,8- Acad. Sci. US; (1937); 23; 615-620; DE 2,106,675; US trichloro-1,3,4,6,7,9,9b-heptaazaphenalene of the for- 10 4,205,167; furthermore Finkel’shtein,A.L.; Russ. Chem. mula (I) Rev.; (1964); 33(7); 400-405). [0005] At present two fundamentally different proce- dures are known for obtaining the cyameluric chloride of formula (I). On one hand compound (I) is obtained by 15 reaction of C6N7O3(R)3, cyameluric acid (when R=H) or an alkaline cyamelurate (when R=Na, K, etc) with phos- phorous pentachloride in a closed system (see Rede- mann,C.E.; J. Am. Chem. Soc.; (1940); 62; 842-846). In this original procedure, done in solid state without any 20 solvent or liquid phase in a sealed tube at 230 °C, a pres- sure develops due to formation of volatile POCl3 and, in order to avoid bursting of the ampoule, the reaction had therefore occasionally to be interrupted and the positive pressure to be discharged. 25 [0006] In a later work of Schroeder and Kober (see Schroeder,H.; J. Org. Chem.; (1962); 27; 4264) it is re- ported that the reaction using a sealed bomb tube did not have to be interrupted and that after finishing and upon opening of the tube no positive pressure was de- 30 tectable. Attempts to avoid the use of a sealed system is also known as 2,5,8-trichlorotri-s-triazine and desig- by replacing the PCl5 with phenylphosphorous tetrachlo- nated as cyameluric chloride in this invention. ride (C6H4PCl4) were not successful. [0007] According to Neeff (see DE 1,102,321) it is pos- BACKGROUND OF THE INVENTION sible to perform the chlorination in an open system using 35 boiling o-dichlorobenzene as a reaction medium or sol- [0002] Aromatic nitrogen heterocycles have a wide va- vent. However, aromatic chlorinating solvents are fre- riety of uses in coordination chemistry and optical sci- quently carcinogens. They are difficult to be completely ence. In this sense, s-triazine is widely used in synthetic removed from the product due to their relatively low vol- chemistry, coordination chemistry and optical and mag- atility and high affinity to the aromatic π-system of the netic studies, also is playing a key role in molecular routes 40 heptazine. Such contamination is particularly problemat- to carbon nitride (CNx) materials. On the other hand hav- ic, if the final product synthetized from the cyameluric ing as final objective to incorporate larger C-N fragments chloride is to be used in a human environment. in precursors of this aromatic nitrogen heterocycles, one [0008] The separation of side products of the chlorin- of the most studied ones has been the 1,3,4,6,7,9,9b- ation (phosphoryl chloride POCl3, alkali chloride and pos- heptaazaphenalene ring system (also known as tri-s-tri- 45 sibly phosphates) was accomplished by both proce- azine or s-heptazine) (see Miller,D.R.; J. Am. Chem. dures, Redemanns and Schroeder, via washing with wa- Soc.; (2004); 126; 5372-5373). ter followed by vacuum filtration. This is disadvanta- [0003] In this way, the "azaaromatic chlorides" which geous, since cyameluric chloride is very sensitive to hy- are defined as aromatic compounds containing many drolysis. Even when ice water at 0°C is used (see C=N-Cl subunits, represents a remarkable class of inter- 50 Schroeder procedure) a large part of the product is de- mediates which display extensive networks of intermo- composed to form cyameluric acid. lecular nitrogen-chloride donor-acceptor interactions in [0009] Own attempts of the inventors indicated that the the solid state as has been described in the literature fine particle size of the cyameluric chloride caused long (see Xu, K.; J. Am. Chem. Soc.; (1994); 116; 105). filtration times. This implies - in combination with the re- [0004] Cyameluric chloride is a valuable intermediate 55 sidual moisture of the filter cake - a problem, to which for the synthesis of different derivatives, such as gelling also by use of a filter press as well as immediate evac- agents for aliphatic hydrocarbons (see US 3,089,875), uation of the filter cake in a desiccator over phosphorous fluorine-containing oxidants which can be used as addi- pentoxide could not be solved satisfactorily. 2 3 EP 1 854 797 A1 4 [0010] Further attempts to purify the product by subli- [0017] In one preferred embodiment the method ap- mation under atmospheric pressure and with high vacu- plied for removing melamine as well as other molecular um were not successful according to Redemann refer- cyanamide derivatives from the starting material is by ence. pyrolysis that is carried out applying the following tem- [0011] Experiments of the inventors with a commercial 5 perature scheme: sublimation set-up consisting of a vacuum recipient and a water-cooled separating surface, confirmed these find- a. heating from room temperature to between 100 ings. °C and 200°C, preferably from room temperature to [0012] Pure cyameluric chloride can be obtained by a 120 °C in 60 minuts, preferably in 30 minutes procedure described by Gremmelmaier (see US 10 b. maintain between 100 °C and 200°C, preferably 4,205,167). In this patent, chlorine cyanide CI-CN or maintain 120 °C during at least 2 hours, preferably evaporated cyanuric chloride is transferred to a cyame- during 4 hours luric chloride under addition of atmospheric oxygen at an c. heating from between 100 °C and 200°C to be- activated charcoal catalyst at 400 °C. The cyameluric tween 400 °C and 800°C, preferable from 120 °C to chloride which is formed is obtained as a mixture with 15 560 °C in between 1 and 3 hours, preferably in 2 remaining starting material cyanuric chloride. The prod- hours uct is collected in a flask which is heated to 200 °C, while d. maintain between 400 °C and 800°C, preferably the cyanuric chloride condenses in another flask at 20 maintain 560 °C during at least 1 hour, preferably °C. This procedure is characterized by the following dis- during 2 hours followed by cooling down. advantages: relative low yield (31.7 mass percentatge of 20 the cyanuric chloride used as starting material), relatively [0018] In another embodiment the method applied for complicated set-up because mass flow controllers are removing melamine as well as other molecular cyana- required for controlling the amount of starting material mide derivatives from the starting material is via Soxhlet- and air, difficult adjustment of the evaporation rate of solid extraction with water during at least 24 hours, preferably cyanuric chloride and a multiple zone furnace and/or sev- 25 during 48 hours and posterior evaporation of the resulting eral furnaces with separate regulation, arranged into a aqueous solution by known means as rotation evapora- row and connected with joints which have to be heated tor. to >200 °C are necessary in order to prevent condensa- [0019] Finally in another embodiment the method ap- tion of the product which might cause problems with the plied for removing melamine as well as other molecular tightness of the glass joint between the reactor and the 30 cyanamide derivatives from the starting material is via receptacles, specially the temperature stability of the extraction with water, preferably at temperatures up to used sealing material. 85 °C. [0020] In particular melamine otherwise causes prob- DISCLOSURE OF THE INVENTION lems during the following process steps as impurities in 35 x the form of cyanurates such as (H3-xC3N3O3) or cyanuric [0013] The present invention includes several im- chloride.
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