A METHOD FOR PREPARING 2-PYRAZOLIN-5-ONES FROM 1,2,4-OXADIAZOLES

Abstract: The method comprises forming a liquid reaction system of a base catalyst and a 1,2,4-oxadiazole in an organic liquid reaction medium and heating the reaction system to a temperature sufficient to cause the 1,2,4-oxadiazole to be rearranged to a 2-pyrazolin-5-one.

Description: A METHOD FOR PREPARING 2-PYRAZOLIN-5-ONES FROM 1,2,4-OXADIAZOLES This invention relates to a method for preparing 2-ρyrazolin-5-ones from 1,2,4- oxadiazoles. The 2-pyrazolin-5-ones are particularly useful as color forming couplers or as intermediates in preparing color forming couplers which produce dyes in photographic elements . It is well known in the photographic art that 2-pyrazolin-5-ones represented by the structural formula (wherein each of R , R and R is hydrogen, halo, alkyl, or alkoxy, and Z is an alkyl, acyl or aryl radical) are useful as color forming couplers or as intermediates in preparing color forming couplers useful for producing dyes in photographic elements. Many references describe the use of such 2-pyrazolin-5-ones in photographic elements and also describe methods for synthesizing such compounds. See, for example, U. S. Patents 3,419,391; 3,062,653; 2,865,748; 2,600,788; and the patents referred to therein, all of which are hereby incorporated herein by reference. OMPI It would be desirable to have a new method for the synthesis of 2-pyrazolin-5-ones which is more efficient and more economical than the previously known methods. The present invention unexpectedly provides such a method. It involves the rearrangemment of certain 1,2,4-oxadiazoles to the corresponding 2-pyrazolin-5-ones. In general regard to oxadiazole rearrangements, U. S. Patent 3,927,025, to Korbonits et al, and Ruccia et al, A New Rearrangement in the 1,2,4-Qχadiazole Series, in J. Chem. Soc. Chem. Co m. , p. 866 (1970) are relevant. These references describe rearrangements of 1,2,4-oxadiazoles, but the rearrangements described are carried out in aqueous solutions and yield pyrazolines or triazolinones, which are compounds significantly different, chemically, from 2-pyrazolin-5-ones. These references do not describe or suggest any new method for the synthesis of 2-pyrazolin-5-ones. The invention provides a method for preparing a 2-pyrazolin-5-one, which method is characterized by: (a) forming a substantially non-aqueous liquid reaction system containing: (1) an organic liquid reaction medium, (2) a base catalyst and (3) a 1,2,4-oxadiazole represented by the structural formula -£JREΛ OMΓI wherein each of R1, R2 and R3 is hydrogen, halo, alkyl having from 1 to 5 carbon atoms, or -alkoxy having from 1 to 5 carbon atoms; and J is alkyl having from 1 to 20 carbon atoms, phenoxyalkyl with the alkyl portion thereof having from 1 to 20 carbon atoms, phenyl, alkoxyphenyl, a 5-membered aromatic heterocyclic radical, phenoxyacyl- aminophenyl, or phenoxyalkyl substituted with one or more, nitro radicals in at least one of the para or ortho positions; and (b) heating said reaction system to a temperature sufficient to cause said 1,2,4-oxadiazole to rearrange to the corresponding 2-pyrazolin-5-one represented by the structural formula: wherein R 1, R2, R3 and J are as defined hereinabove. The method of the present invention is more efficient (producing higher yields) and more economical than previously known methods of synthesizing 2-pyrazolin-5-ones. The l;2,4-oxadiazole starting materials for the method of this invention are conveniently prepared by known methods. For example, 2-(5-methyl-l,2,4-oxadiazol-3-yl)-2' ,4* ,6'- trichloroacetanilide is prepared by the following reaction sequence: OMPI first, 2,4,6-trichloroaniline is converted to 2-chloro-2* ,4' ,6'-trichloroacetanilide in 92-95 percent yield by heating with chloroacetyl chloride under reflux for 3 hours in an aromatic hydrocarbon solvent such as toluene or xylene, i.e., the resulting compound is then reacted with sodium cyanide in water and N,N-dimethylformamide (DMF) at room temperature for 18 hours to give 2-cyano-2' ,4' ,6'-trichloroacetanilide in 93-95 percent yield, i.e., the product _ heated next with hydroxyiamine in nqμma ethanol under reflux for 45 minutes C o . obtain 3 «&P 3-(2,4,6-trichloro~ nilino)propionaaidoκi_ae in 86 percent yield, i.e , the amidoxiaβ Is then converted t_ the 1,2,4-oxadiazole in *5 percent yield by ..sirring with acetic anhydride ia aca ic acid at rsc t α temperature for 2 høirs ar.c then heating -i.-ic β r reflux for 1.5 hours, i.e., BAD ORIGINAL The present method is then used to convert the ,2^4-oxadiaaola :o * ha 2- yrazolin-5-one, e.g., eatin a. solution -of . otass&um hydroxide and -CS-oe yl-l^lZ^-cacad' az l-S- ^ 1 ,4' ,6'-trichloro- acetanilide in anhydrous ehanol under reflux at a temperature of SO β C for 8 to 14 hours to yield 3-acetamido-l-(2,4,δ-trichlcrophenyl)-2-pyrazolin-5- one , . e. , As illustrated in Example 1 below, the method of the invention produces significant yields of the desire ' 2-ρ razoIin-5-one when carried out in an organic medium. In contrast, insignificant _--> yields (in a commercial sense) are obtained when the rearrangement is attempted in an aqueous medium. By !! liquid reaction system" we mean a solution or iAWιf_ y > " ,..» BAD ORIGINAL dispersion of the 1,2,4-oxadiazole and the base catalyst in an organic liquid reaction medium. In other words, the system is substantially non-aqueous or anhydrous. The base catalyst is included in the reaction system in an effective catalytic amount and can be chosen from any of the well known base catalysts. Examples of base catalysts useful in the method are alkali hydroxides, alkali alkc-cides, alkali, triphosphates, and alkali carbonates- Specific examples of such base catalysts are potassium hydroxide, sodium methoxide, and potassium carbonate. The yields obtainable by the method of the invention are somewhat dependent upon the organic liquid reaction medium included in the reaction system and the temperature at which the reaction is carried out. The reaction is essentially a competition between the rearrangement and solvolysis. Higher temperatures and/or organic liquid media which are aprotic solvent,, will favør the rearrangement over solvolysis and, thus, increase the yield. Generally, a temperature up to 125°C will produce significant yields. A temperature of at least 80°C in a precis organic solvent (i.e., an organic solvent having acidic hydrogen atoms, such as a hydrogen atom attached to a nitrogen or oxygen atom, e.g., ethanol or methanol) will give yields usually greater than 40 percent. Usingf ' a protic solvent with a higher boiling point (e.g., 2-methoxyethanol, b.p. 124°C) will ' enable the reaction to be carried out at a higher temperature (e.g., approximately 125°C) axsd give yields usually higher than about 70 percent. BAD ORIGINAL An aprotic solvent (i.e., a polar solvent of moderately high dielectric constant having no acidic .hydrogens, e.g., N,N-dimethylformamide [DMF])or - dimethylsulfoxide (DM50) is preferred, because it inherently has less tendency toward solvolysis. Yields approaching 90 percent are achievable by using an aprotic organic solvent as the reaction medium. Using an oxadiazole having the formula set out above wherein J is a nitrophenoxyaikyl radical, the initial rearrangement proceeds further, spontaneously, to undergo what is generally referred to as a Smiles rearrangement to give a 3-nitroanilino-2-pyrazolin-5-one, as illustrated in Example 20 below. The following Examples further illustrate the practice of the invention. Examples 1-20 illustrate the method of the invention as practiced on 1,2,4-oxadiazoles to produce 2-pyrazolin-5-ones. Example 1 -9- To a solution of 10 g of potassium hydroxide in 200 ml of anhydrous ethanol was added .20 g of 2-(5-methyl-l,2,4-oxadiazol-3-yl. - 2' ,4' ,6'-trichloroacetanilide. The mixture was heated under reflux for 10 hours. After it cooled, the mixture was acidified with 20 ml of acetic acid and concentrated to almost dryness under reduced pressure. The residue was slurried in water, collected, and dried. The crude product was stirred with 200 ml of hexane for 15 min. , and the hexane solution was separated from undissolved solids by filtration. The solid residue was dissolved in hot ethanol and allowed to crystallize overnight. There was obtained 9.6 g (48X) of 3-acetamido-l-(2,4,6- trichlorophenyl)-2-ρyrazolin-5-one,mp 234-235.5°C, and 1.5 g (122) of the hydrolysis by-product, 2,4,6- richloroaniline. The procedure was repeated using a mixture of 20% water and 801 ethanol as the solvent instead of the anhydrous ethanol used above. This time the yield of 3-acetamido-l-(2,4,6-trichlorophenyl)- 2-pyrazolin-5-one was very poor, i.e., only 8%, while a 57X yield of 2,4,6-trichloroaniline was obtained. This illustrates that, in contrast to the excellent yields produced in an organic medium, very poor yields are obtained when the rearrangement is run in an aqueous medium. OMPI Examoles 2-6 Cl Cl The above base- catalyzed rearrangement of 2-(5-methyl-l,2,4-oxadiazol-3-yl)-2 ' ,4' ,6 f -trichloro- acetanilide to 3-acetamido-l- (2,4, 6- trichlorophenyl)- 2-pyrazolin-5-one was run under several different reaction conditions * The results are summarized in the following Table I. TABLE I Organic Liquid Reaction Reaction Percent Yield ofc Example Number Base Catalyst Reaction Medium Temperature Time 2-Pyrazolin-5-o 2 sodium methoxide anhydrous ethanol 80°C 16 hrs. 44 , 3 sodium' methoxide 2-π.ethoxyethanol ( methyl cellosolve) 125°C 3 hrs. 74 4 sodium methoxide N,N-dimethyl£orα_amlde 110°C 2 hrs. 80 (DMF) 5 potassium DMF 110°C 2 hrs. 80 carbonate ppoottaassssiiuumm DMF 110°C 2 hrs. 75 hydroxide Example 7 To a solution of 2.2 g of potassium hydroxide in 100 ml of anhydrous ethanol was added 10 g of 2- {5-[1-(2,4-di-tert.-pentylphenoxy)pentyl]-1,2,4-oxa- diazol-3-yl}-2' ,4' ,6'-trichloro-acetanilide. The mixture was heated under reflux for 21/2 hrs. After it was cooled, the mixture was acidified with 3 ml of acetic acid and-.ethanol was evaporated under reduced pressure. The residual oil was taken up into 100 ml of toluene, washed with water, dried over anhydrous magnesium sulfate, and evaporated to dryness under reduced pressure. The residual yellow oil was " REA O _: crystallized from hexane. There was obtained 8.9 g (891) of 3-[2-(2,4-di-tert.-pentylphenoxy)- .hexanoylamidoI-l-(2,4,6-trichlorophenyl)-2-pyrazolin-5- one as colorless crystals, mp 98-100°C. Examples 8-18 The following list of examples illustrates additional preparations of l-aryl-3-acylamido-2-pyrazolin-5-ones according to the above equation using a procedure similar to that described in Example 7. In each example, starting material, base/solvent, reaction temperature/reaction time, product, its melting point and yield are listed in order. Example 8; 2-{5-[l-(m-Pentadecylphenoxy)- propyl]-1,2,4-oxadiazol-3-yl}-2',4' ,6'-trichloro- acetanilide( 1 -R -R 3 -Cl) , -$TF£H ' A _OM?I KOH/EtOH, reflux/2 __*» • » 3-[2-(m-pentadecyl « ox )butyramido3- l-(2,4,6-trichioroph«Pyl)-2-ρyrazolin-5-one, mp 131-132°C, 85%. Example 9; %~ 5-[l-(m-Pentadecylphenoxy)- propyl3-l ,2 , -oxadial|l-3-yl3-2 ' -chloro-4' ,6 • -dimethyl- acetanilide (R^Cl, * « * -CH- 3 ) , KOH/MeOH, reflux/21-2 hrs., l-(2-chloro-4,6-dim»«i l ylphenyl) / -3- [2-(m-pentadecylphefi&J-y)butyramido3-2-pyrazolin-5-one, KOH/EtOH, reflux/3 hrs., 3-[2-(3-tert-butyl-4-hydroxyρhenoxy)-tetradecanoylamido -l-(2,4,6-trichlorophenyl)-2-ρyrazolin-5-one, ap 86-91°C, 69%. Example 11; 2-(5-methyl-l,2,4-oxadiazol-3- yl) acetanilide (R i -R 2 -R 3 -H, J-CH- 3 ) , KOH/EtOH, reflux/41/2 hrs., 3-acetamido-l-phenyl-2-pyrazolin- 5-one, mp 207-213°C (dec), 42% Example 12; 2-(5-Methyl-l,2,4-oxadiazol-3-yl)-4'-methoxyacetanilid_ (R 1 -R 3 -H, R 2 -CH 3 0-, J-CH- 3 ), KOH/MeOH, reflux/4 hrs., 3-acetamido-l-(p-methoxyphenyl)~ 2-pyrazolin-5-one, mp 234-236°C, 24%. Example 13; ' ,4',6'- trichloroacetanilide (R 1^-R^- ^-Cl, J-CH- 3 CH 2 -), KOH/EtOH, reflux/8 hrs,, 3-proρionamido-l-(2,4,6-trichloro- phenyl)-2-pyrazolin-5-one, mp 167-170.5 β C, 42%. Example 14; 2-(5-n-Propyl-l,2,4-oxadiazol-3~yl)~ _ 5 3 2',4' ,6'-trichloroacetanilide (R~-*?." » R *=C1. J-CH- 3 CH 2 CH 2 -) , KOH/EtOH, reflux/3 hrs., 3-butyramido-1-(2,4,6-trichlorophenyl)-2-pyrazolin~5- one, mp 153-158°C, 44%. Example 15; 2-(5-tert.-Butyl-l ,2 ,4-oxadiazol-3-yl) - , J»(CH- 3 ) 3 C-, KOH/EtOH, reflux/5 hrs . , 3-pivaloylamido-l- (2 ,4, 6-trichlorophenyl) -2*pyraz •fcr-.l - i "1 r τ » _ s one, mp 182-186 C , 69% . • BAD o^' * " ■v ~b ■ u -r?> 5 (2,4,6-trichlorophenr 1 )- 2 -Py Tazolin - 5 " one » ffl P 278-280°C, 62%. Example 1 j 2-[5-(p-Methoxyphenyl)-l_2,4-oxadiazol-3- yl -2',4 , ,6 , -trichlcto*cetanilide (R -R -R -Cl, 0 J-p-CH 3 0-C 6 H 4 -) , KGH/EtOH, reflux/12 hrs., 3-(p-methoxybenzoyl)**ido-l-(2,4,6-trichlorophenyl)-2- pyrazolin-5-one, mp llδ-220°C, 49%. Example β » 2-[5-(2-Furyl)-l,2,4-oxadiaz.ol-3-yi3- 15 2 , ,4 , ,6 , -trichloroafc#tanαida <*_ M * "* " cl » J-2-furyl) , KOH/EtOS. xw^n / - hrs. , - 2-furo lamido -l* 2. 4 » 6 ' tr i c lo Q - β phenyl) -2-pyrazolin**-° ne * m S 240-245 β C (dec), 75%. A mixture of 13.6 g of 2-[[5-{3-[(2,4- di-tert.-pentylphenoxy)acetamidoIpheny1}-1,2,4- oxadia2ol-3-yl3]-2' ,4' ,6'-tri-chloroacetanilide, 5.6 g of anhydrous potassium carbonate, and 25 ml of N,N-dimethylformamide (DMF) was heated at 110°C with vigorous stirring for 2 1/2 hours. The reaction mixture was poured into water and the precipitate was recrystallized twice from acetic acid and ethano - There was obtained 9.0 g (68X) of 3-{[3-<2 » 4- di-tert.-pentylphenoxy)acetamido]-benzoylamido}-1- (2 3 4,6-trichlorophenyl)-2-pyrazolin-5-one as a colorless solid, mp 174.5-178°C. Similar results are obtained when the solvent is dimethylsulfoxide (DM5G) . The same oxadiazole did not give the desired 2-ρyrazolin-5-one when the low-boiling procic solvent, anhydrous ethanol, was used instead of the high-boiling aprotic solvent DMF, thus illustrating the preferability of higher temperatures and/or aprotic solvents for the practice of the inventio . To a solution of 5 g of potassium hydroxide in 75 ml of anhydrous methanol was added 10 g of , 2-[5-(p-nitrophenoxyaethyl)-l,2,4-oxadiazol-3-yl]-2' ,4 f t 6'-trichloroacetanilide. The mixture was heated under 5 reflux for 2 hours. The reaction did not stop with 3-£(p-nitro-phenoxy)acetamido3-1-(2,4,6- trichlorophenyl)-2-pyrazolin-5-one but proceeded further, by a Smil** rearrangement, to give 3-(p-nitroanilino)-1"(2,4,6-trichlorophenyl)-2-ρyrazolin 10 -5-one. " At the tiά of the reaction, the mixture was allowed to cool to room temperature, acidified with 10 ml of acetic acid, diluted with 70 ml of water, and then allowed to s * 4 a room temperature overnight. The product was collected, washed with water and 15 ethanol, and dried * There was obtained 3.8 g (43%) of 3-(ρ-nitroanilino)»*-(2»4,6-trichlorophenyl)-2-pyrazolin -5-one as yellow crystals, mp 295-298°C. Comparatt** Examples 1-4 illustrate attempted rearrangements of sasadiazoles which are not within the 20 scope of the invention. These examples illustrate the unexpected nature Φ£ tϊle results of the practice of the present invention by showing that 1,2,4- oxadiazoles having «*rtai_. substituent groups outside the scope of the iswen ion are not converted to the 25 corresponding 2-py3-wεolin-5-ones by subjecting them to the reaction conditions of.the method of the present invention. Comparative Example 1 to a The follo«s*tg compounds failed to give the 30 corresponding l-ε*_-*εituced-3-acylamino-2-pyrazolin- 5-ones under any «& the reaction conditions described in Examples 1-6. - • Amu.?*'. ~ t _ q -19- Comparative Example 1: 2-(5-Methyl-l,2,4-oxadiazol-3-yl)-4'-nitro- acetanilide (R 10« p-NO 2 -C 6 H 4 «, R 12 «CH 3 -) . 5 Comparative Example 2: N-Benzyl-2-(5-methyl-l,2,4-oxadiazol-3- yl)acetamide (R 10 »phCH 2 -, R 12 -CΪ_ 3 -) . Comparative Example 3: 2-[5-(p-Nitrophenyl)-l,2,4-oxadiazol-3- 10 yl_-2' ,4" ,6'-trichloroacetanilide (R 10 -2,4,6-Cl 3 -C 6 H 2 -, R 12 -p-NO 2 -C 6 H 4 -) . Comparative Example 4: 2-[5-(m-Nitrophenyl)-1,2,4-oxadiazol-3-yl]- 2' ,4',6'-trichloroacetanilide 15 (R 10« 2,4,6-C1 3 -C 6 H 2 -, R 12 «m-N0 2 -C 6 H- .

Claims: Clai s : 1. A method for preparing a __-ρyrazolin-5-one, which method is characterized by: a) forming a substantially non-aqueous, liquid reaction system containing: 1) an organic liquid reaction medium, 2) a base catalyst, and 3) a 1,2,4-oxadiazole represented by the structural formula: wherein each of R 1, R2 and R3 is hydrogen, halo, ' alkyl having from 1 to 5 carbon atoms, or alkoxy having from 1 to 5 carbon atoms; and J is alkyl having from 1 to 20 carbon atoms, phenoxyalkyl with the alkyl portion thereof having from 1 to 20 carbon atoms, phenyl, alkoxyphenyl, a 5-membered aromatic heterocyclic radical, phenoxyacylaminophenyl, or phenoxyalkyl substituted with one or more nitro radicals in at least one of the para or ortho positions; and b) heating said reaction system to a temperature sufficient to cause said 1,2,4-oxadiazole to rearrange tcT ' the corresponding 2-pyrazolin-5-one represented by the structural formula: IAD ORIGINAL wherein R 1, R , R3 and J are as defined hereinabove. 2. The method according to claim 1, characterized in that said reaction system is heated to a temperature of from 80°C to 125°C during said heating step. 3. The method according to claim 2, characterized in that said base catalyst is an alkali hydroxide, an alkali alkoxide, an alkali triphosphate, or an alkali carbonate. 4. The method according to claim 3, characterized in that said organic liquid reaction medium is a protic organic solvent. 5. The method according to claim 3, characterized in that said organic liquid reaction medium is an aprotic organic solvent. 6. The method according to claims 4 or 5 t characterized in that said organic liquid reaction medium is ethanol, methanol, 2-methoxyethanol, or N,N-dimethylformaπ-ide. 7. The method according to claim 6, characterized in that said 1,2,4-oxadiazole is: a) 2-(5-methyl-l,2,4-oxadiazol- 3-yl)-2' ,4' ,6'-trichloroacetanilide; b) 2-(5-methyl-l,2,4-oxadiazol- 3-yl)-acetanilide; c) 2-{5-[l-(2,4-di-tert.- pentylphenoxy)-pentyl3-1,2,4-oxadiazol-3-yl} - 2' ,4' ,6'-trichloroacetanilide; d) 2- 5-[l-(m-pentadecylphenoxy)- propyl]-l,2,4-oxadiazol-3-yl} -2 T ,4 « ,6'-trichloro¬ acetanilide; e) 2-{ 5-[l-(m-pentadecylphenoxy)- propyl]-l,2,4-oxadiazol-3-yl} -2'-chloro-4' ,6'- dimethyl-acetanilide; f) 2-(5-methyl-l,2,4-oxadiazol- 3-yl)-4'-methox -acetanilide; g) 2-(5-ethyl-l,2,4-oxadiazol- 3-yl)-2' ,4' ,6'-trichloroacetanilide; h) 2-(5-n-propyl-l,2,4-oxadiazol- 3-yl)-2' ,4' ,6 ! -trichloroacetanilid ; i) 2-(5-tert.-butyl-1,2,4-oxadiazol- 3-yl)-2' , ' ,6'-trichloroacetanilide; j) 2-(5-phenyl-l,2,4-oxadiazol- 3-yl)-2' ,4' ,6'-trichloroacetanilide; k) 2-[5-(p-methoxyphenyl)-1,2,4- oxadiazol-3-yl]-2' ,4' ,6*-trichloroacetanilide; 1) 2-[5-(2-furyl)-l,2,4-oxadiazol- 3-yl]-2 r ,4' ,6'-trichloroacetanilide; m) 2-[[5-{3-[(2,4-di-tert.- pentylphenoxy) " acetamido3-phenyl] -1,2,4-oxadiazol- 3-yl -2' ,4' ,6'-trichloroacetanilide; or n) 2-[5-( -nitrophenoxy eth 1)- 1,2,4-oxadiazo1-3-yl -2 l ,4' ,6 • -trichloroace anilid , 8. The method according to claim 5, characterized in that said 1,2,4-oxadiazole is 2-[[5-{3-[2,4-di- ert.-pentylphenoxy)acetamido3- phenylJ-l^^-o adiazol-S-y }^ 1 ^'^'- trichloroacetanilide and said 2-pyrazolin-5-one iβ 3-{ [3-(2,4-di-tert.-pentylphenoxy)acetamido3benzo 1- amido}-1-(2,4,6-trichlorophenyl)-2-pyrazolin-5-one.

Inventors: KIM CHANG KYU, MAGGIULLI CATALDO A, ZIELINSKI PAUL A
Applicants: EASTMAN KODAK CO
Application year: 1981
Main classification: C07D231
IPC codes: C07D231, C07D271, C07D307, C07D405