PROCESS FOR MAKING 2-ARYL BENZ(OX, THI, IMID)AZOLES AND 2-AMINOARYL AMINOBENZ(OX, THI, IMID)AZOLES

Abstract: 2-(Aryl)-benz(ox, thi, imid)azoles are prepared by reacting an aromatic aldehyde with hydroxylamine to form an aromatic aldehyde oxime, halogenating the oxime to form an aromatic hydroxamoyl halide, and then reacting this halide with certain aromatic amine compounds. The products may be nitrated and then reduced to form the corresponding diamines, which are useful in making PIBX polymers.

Description: PROCESS FOR MAKING 2-ARYL BENZ(OX, THI, IMID)AZOLES AND 2-AMINOARYL AMINOBENZ(OX, THI, IMID)AZOLES This invention relates to a process for making 2-aryl benz(ox, thi, imid)azoles and 2-aminoaryl aminobenz(ox, thi, imid)azoles. The term "benz(ox, thi, imid)azole" is used herein as a shorthand term to designate an oxazole, thiazole or imidazole group which is fused to an aromatic ring at the 4 and 5 positions. Polyimide benz(ox, thi, imid)azole (PIBX) polymers can be prepared by reacting a dianhydride with a diamine containing one or more benz(ox, thi, imid)azole groups. See, for example, U.S. Patent No. 4,087,409 to Preston, incorporated herein by reference. Among the useful benz(ox, thi, imid)azole-containing diamines are those in which the 2-position of the oxazole ring is substituted with an aminoaryl group. Among the diamines of the latter type are those represented by the structure: wherein X is-O-, -S-, or-NH-. These latter amines can be prepared by reacting an amino benzoic acid with 2,4- or 2,5-diamino phenol, 2,4- or 2,5-diamino phenyl mercaptan, or 1 ,2,4-triaminobenzene (when X is -0-, -S-, and -NH-, respectively). For example, it is known to prepare 2-(m- aminophenyl)-aminobenzoxazole (DAMBO) by reacting 2,4-diaminophenol with meta- or para-aminobenzoic acid in the presence of polyphosphoric acid. Unfortunately, however, this process suffers from several drawbacks. The reaction mixture requires extensive neutralization and, thus, forms large volumes of aqueous phosphate salts as a waste stream. The product must be purified extensively through repeated sublimations in order to be useful as a monomer. In addition, the diaminophenol and aminobenzoic acid starting materials are expensive and not readily available. For these reasons, it would be desirable to provide an alternate method for making DAMBO as well as other 2-aminoaryl aminobenz(ox, thi, imid)azoles. In one aspect, this invention is a process for preparing a 2-(aryl)-benz(ox, thi, imid)azole, comprising: (a) contacting an aromatic aldehyde with hydroxylamine under conditions such that an aromatic aldehyde oxime is formed; (b) contacting said aromatic aldehyde oxime with a halogenating agent under conditions such that an aromatic hydroxamoyl halide is formed and (c) contacting the aromatic hydroxamoyl halide with an aromatic amine compound which has a primary amine group ortho to a hydroxyl group, a thiol group or another primary amine group to form a 2-(aryl)-benz(ox, thi, ιmιd)azole In this process, both the aromatic aldehyde and the aromatic amine compound may be nitro- substituted. In such case, the nitro group or groups may be reduced to primary amine groups after step (c) In the case where neither, or only one of the aromatic aldehyde and the aromatic o amine compound is nitro-substituted, the benz(ox, thi, ιmιd)azole may be nitrated after step (c) so that following the nitration, both the benz(ox, thi, ιmιd)azole and the aromatic substituent at the 2-posιtιon contain a nitro group These nitro groups may be then reduced to amines Steps (a), (b) and (c) can be performed under mild conditions to obtain high yields of benz(ox, thi, ιmιd)azole at essentially 100% selectivity and do not require the use of 5 polyphosphonc acid. Moreover, the process of this invention makes use of relatively inexpensive starting materials In the first step of this process, an aromatic aldehyde is contacted with hydroxylamine under conditions such that an aromatic aldehyde oxime is formed By "aromatic aldehyde oxime," it is meant a compound in which a group represented by the 0 structure: -CH = N-OH is bonded directly to an aromatic nucleus of an aromatic ring structure The aromatic aldehyde is a compound having a -CHO group directly bonded to an aromatic nucleus of an aromatic ring structure. Suitable aromatic ring structures to which 5 the -CHO group is bonded include pyπdine, benzene and fused ring systems such as anthracene, naphthalene. The aromatic ring structure may be unsubstituted or substituted However, any substituted ring structure must contain either a hydrogen or a nitro group attached to an aromatic nucleus, or else at least one of the substituent groups must be capable of being replaced by a nitro group after the benz(ox, thi, ιmιd)azole is formed In addition, any 0 substituent group should not react under the conditions of the reaction with hydroxylamine with the aromatic aldehyde, or of the subsequent reactions with a halogenating agent and with the aromatic amine compound Suitable substituents include phenyl, phenoxyl or -S0 2 - (CβHs) It is preferred, but not necessary, that the aromatic aldehyde contain a nitro group bonded to an aromatic ring Benzaldehyde and mononitrobenzaldehyde are preferred 5 aromatic aldehydes, with m- and p-nitrobenzaldehyde being especially preferred The hydroxylamine (H 2 NOH) may be and preferably is used in the form of a salt of a protic acid, such as the HCI salt. The hydroxylamine is preferably used in a slight excess relative to the aromatic aldehyde The aromatic aldehyde and the hydroxylamine are advantageously contacted in the presence of a solvent or diluent Preferred solvents are polar materials in which both the aldehyde and the hydroxylamine are soluble. Alternatively, nonsolvents can be used as diluents It is also preferred that the solvent be one which boils within the preferred or more preferred temperature range described below, so the reaction may be conducted under refluxmg conditions. Suitable solvents include, for example, ethanol, methanol, isopropanol, 1 ,4-dιoxane, tetrahydrofuran and polar aprotic solvents that are inert to the reactants and the products, as well as toluene and benzene. The reaction is preferably conducted at an elevated temperature at which the aromatic aldehyde does not degrade. A preferred temperature is from 30 C C to 120°C, with a temperature from 50°C to 95°C being more preferred. At the more preferred temperature, a reaction time of from 1/2 hour to 8 hours is generally sufficient to essentially complete the reaction In the formation of the aromatic hydroxamoyl halide, the contacting of the aromatic aldehyde with hydroxylamine is preferably carried out under conditions substantially in the absence of caustic or base, such as a tertiary amine (e. g., tnethylamine), wherein substantially, in the absence of caustic or base, is an amount of at most about 5% equivalent weight of the hydroxamoyl halide formed from the aldehyde oxime. Preferably the amount of caustic or base is at most about 2%, even more preferably at most about 1 %, and most preferably at most about 0.2% equivalent weight of the hydroxamoyl halide. The resulting aromatic aldehyde oxime is then reacted with a halogenating agent under oxidizing conditions to form the corresponding aromatic hydroxamoyl halide. By "aromatic hydroxamoyl halide," it is meant a compound in which a group represented by the structure: -CA = N-OH is bonded directly to a nucleus of an aromatic ring structure. In the foregoing structure, A represents a halogen atom, preferably chlorine or bromine The halogenation proceeds well even under mild conditions and, for that reason, it is preferable to use mild halogenating agents and conditions in order to avoid halogenation at other sites on the aromatic aldehyde oxime molecule Suitable halogenating agents include chlorine (Cl 2 ), bromine (Br 2 ), hypochlorous acid (HOCI), hypobromous acid and materials which generate hypochlorous or hypobromous acid in situ Chlorine, bromine, hypochlorous acid and hypobromous acid are advantageously used as dilute solutions, preferably as aqueous solutions Materials which produce hypochlorous acid in situ include, for example, aqueous mixtures of sodium hypochlorite and a mineral acid, especially HCI ; mixtures of a peroxysulfate salt such as potassium peroxysulfate with HCI and mixtures of N-chlorosucαnamide with aqueous HCI. In analogous fashion, hypobromous acid may be formed in situ from aqueous mixtures of sodium hypobromite and a mineral acid, mixtures of a peroxysulfate salt such as potassium peroxysulfate with HBr and a mixture of N-bromosuccinamide with aqueous HCI In preferred embodiments, the halogenating agent is a mixture of bleach (sodium hypochlorite solution) with a mineral acid, especially HCI, or an aqueous mixture of a peroxysulfate salt with HCI or HBr In any of these preferred embodiments, HCI or HBr may be used in the form of an HCI or HBr salt of N,N-dιmethylformamιde The halogenating agent is advantageously used in at least a stoichiometπc amount, and preferably in slight excess, based on the aromatic aldehyde oxime The halogenation reaction may be conducted in the presence of a solvent or diluent The solvents which are useful for the reaction between the aromatic aldehyde and the hydroxylamine are generally useful in this step as well A suitable temperature for the halogenation step is from -30° to 100°C, preferably from -10° to 40°C The resulting aromatic hydroxamoyl halide is then reacted with an aromatic amine compound having a primary amine group ortho to a hydroxyl group, a thiol group or another primary ammo group In this manner an oxazole, thiazol or imidazole is formed in which an aromatic ring structure corresponding to that of the aromatic hydroxamoyl halide is bonded to the 2-posιtιon The oxazole, thiazole or imidazole group is formed when the aromatic amine compound contains a hydroxyl, thiol or another primary amine group, respectively, ortho to a primary amine group The aromatic amine contains an aromatic ring structure which may be monocyclic or polycyclic The aromatic ring structure may contain substituents other than those mentioned before (that is, the primary amine group and the hydroxyl, thiol or second primary amine group ortho to the primary amine group) However, any substituted ring structure must contain either a hydrogen or a nitro group attached to an aromatic nucleus, or else at least one of the substituent groups must be capable of being replaced by a nitro group after the benz(ox, thι,ιmιd)azole is formed Further, any substituent group should not react under the conditions of the reaction with the aromatic hydroxamoyl halide to form the benz(ox, thi, ιmιd)azole Preferred aromatic amine compounds include those in which the aromatic ring structure is pyπdine, benzene, anthracene, naphthalene, nitropyπdine, nitrobenzene, nitroanthracene, nitronaphthalene, of which benzene and nitrobenzene are more preferred The reaction to form the benz(ox, thi, ιrπιd)azoie can be conducted by mixing the reactants with heating to a temperature from 20°C to 150°C It is advantageous to use a solvent, with those which boil in the stated temperature range being preferred Among the suitable solvents are methyl ethyl ketone, 1 ,4-dιoxane, toluene and chlorobenzene It is preferred to use the aromatic amine compound and the aromatic hydroxamoyl halide in a mole ratio from 0 5 1 to 1 0 5, more preferably from 0 7 1 to 1 0 7 The resulting benz(ox, thi, ιmιd)azole has an aromatic ring structure corresponding to that of the aromatic amine compound fused to the 4 and 5 positions of the benz(ox, thi, ιmιd)azole πng At the 2-posιtιon ot the benz(ox, thi, ιmιd)azole ring there is another aromatic ring structure corresponding to that of the aromatic hydroxamoyl halide If both of the aromatic ring structures of the benz(ox, thi, ιmιd)azole contain a nitro group, a 2-amιnoaryl-amιnobenz(ox, thi, ιmιd)azole is prepared by reducing the nitro groups to amine groups Any method may be used to accomplish this reduαion provided that it selectively reduces the nitro groups and does not hydrogenate the aromatic rings (including the (ox, thi, ιmιd)azole ring) One suitable method is to contact the benz(ox, thi, ιmιd)azole with hydrogen or other hydrogenating agent in the presence of a metal catalyst Suitable metal catalysts include platinum and palladium, organometal c complexes of cobalt, nickel, titanium, zirconium and hafnium The catalyst may be and preferably is supported on a porous support Platinum and palladium are preferred catalysts with platinum on carbon and palladium on carbon being particularly preferred The amount of catalyst is chosen to provide an acceptable reaction rate and, typically, is (but is not limited to) from 1 part by weight catalyst per 5 to 5000 parts of the benz(ox, thi, ιmιd)azole to be hydrogenated It will be understood that many methods for conducting this hydrogenation may be used and the selection of a particular method is not generally critical to this invention In the preferred hydrogenation method, the benz(ox, thi, ιmιd)azole is contacted with hydrogen at a partial pressure of from 0 to 5000 psig, at any temperature at which an adequate reaction rate is achieved, preferably from 25°C to 100"C When one or both of the aromatic ring structures of the benz(ox, thi, ιmιd)azole lacks a nitro group, it is necessary to nitrate the benz(ox, thi, ιmιd)azole before the reduction is done The method by which the nitration is accomplished is not critical provided that undesired side reactions do not occur Accordingly, the known methods for accomplishing ring nitration of aromatic compounds can be used A preferred method is to contact the benz(ox, thi, ιmιd)azole with nitric acid in the presence of sulfuπc acid, preferably at a temperature range of from 0°C to 25°C using conditions that prevent multiple nitrations of either aromatic ring structure It is preferred that, following any nitration, each aromatic ring structure contains only one nitro group Once the needed nitro group or groups are added, they are hydrogenated to the corresponding primary amine as described before The resulting 2-(amιnoaryl)-amιno benz(ox, thi, ιmιd)azole may be recovered from the reaction mixture by filtering out the catalyst and removing the solvent The 2-(amιnoaryl)-amιno benz(ox, thi, ιmιd)azole can be used to make PIBX (polyimidebenzoxazole or polyimidebenzthiazole) polymers by reaction with an aromatic dianhydride, as described in the copending application of Hwang et al entitled POLYAMIC ACIDS AND METHODS TO CONVERT POLYAMIC ACIDS INTO POLYIMIDEBENZOXAZOLE FILMS, Serial No 331 ,775, filed October 31 , 1994 This reaction is typically conducted in two stages In the first stage, the 2-(amιnoaryl)-amιnobenz(ox, thi, ιmιd)azole and the dianhydride are reacted to form a polyamic acid This is readily accomplished by contacting the dianhydride and the 2-(amιnoaryl)-amιnobenz(ox, thi, ιmιd)azole at a temperature from -20°C to 100°C in a polar solvent. The resulting polyamic acid may then be converted to the PIBX by condensing some or all of the amic acid linkages. This is conveniently accomplished by heating the polyamic acid to an elevated temperature which may range up to 600°C, but is preferably 160°C to 280 C C. Alternatively, a ring-closure agent such as acetic anhydride, propnonic anhydride, ketene or isobutyπc dianhydride or salts thereof may be contacted with the polyamic acid to promote formation of imide rings. Following the imidization reaction, it is preferred to further heat the PIBX to a temperature from 300°C to 600°C, which improves tensile properties of the polymer. The PIBX polymer can be used to make films, fibers or other shaped articles. Such articles are conveniently prepared by forming a solution of the PIBO in a suitable solvent and extruding, coating, casting or spraying the solution. Preferably, however, such articles are prepared from the polyamic acid solution, which is imidized after the shaped article is formed. The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. Example 1 In a 1 -liter flask equipped with a reflux condenser and a stirrer was charged 75 grams (0.5 mole) of 4-nitrobenzaidehyde, 500 milliliters of 1 ,4-dioxane and 38 grams (0.55 mole) of hydroxylamine hydrochloride. The mixture was heated to reflux with stirring for five hours and then filtered. The reaction proceeds essentially quantitatively to form a solution containing approximately 0.5 mole of 4-nιtrobenzaldoxιme. The resulting 4-nitrobenzaldoxιme solution was added to 400 additional milliliters of 1 ,4-dioxane, 100 milliliters of dimethylformamide which was saturated with 20 grams (0.55 mole) of HCI and 338 grams (0.55 mole) of a potassium peroxysulfate solution sold by DuPont under the trade designation Oxone. The resulting mixture was stirred for 18 hours using an ice bath to control the exotherm to below 40°C. An additional 5 grams of HCI (dissolved in 50 milliliters of dimethylformamide) was then added and the mixture stirred for an additional 5 hours. The mixture was then washed with acetic acid and water, and 4- nitrophenylchloroxime (4-nιtrophenyl hydroxamoyl chloride) was recovered. 60 Grams (0.3 mole) of the 4-nιtrophenylchloroxιme was mixed with 340 milliliters of ethanol, 60 grams (0.39 mole) of 2-amιno-4-nιtrophenol and 60 milliliters of dimethylformamide. The mixture was heated to reflux for 6.5 hours, filtered, washed with methanol and air dried. Approximately 55 grams of 2-(p-nιtrophenyl)-5-nιtrobenzoxazole were obtained. The 2-(p-nιtrophenyl)-5-nιtrobenzoxazole was dissolved in 500 milliliters of 1 ,4- dioxane. A 10% palladium-on-carbon catalyst (2.0 grams) was added and the mixture heated to 70°C. Hydrogen gas was then bubbled into the solution until liquid chromatography shows that the reduction of the nitro groups was completed The solvent was then evaporated and the resulting product was recrystallized from ethanol 37 5 Grams of 2-(amιnophenyl)-5- aminobenzoxazole was obtained Example 2 Into 500 milliliters of ethanol were dissolved 75 5 grams (0 5 mole) of 4- nitrobenzaldehyde and 38 grams (0 55 mole) of hydroxylamine hydrochloride The solution was heated at reflux for three hours, then poured into water, filtered and dried 79 Grams of 4- nitrobenzaldoxime was recovered 25 Grams (0 15 mole) of the 4-nιtrobenzaldoxιme was combined with 200 o milliliters of 1 ,4-dιoxane and 200 milliliters of concentrated HCI The mixture was cooled to 10°C and then 234 grams of a 5 25% aqueous solution of sodium hypochlorite (0 165 mole) were added dropwise, keeping the temperature of the mixture at 10°C Then, 200 milliliters of ice water were added and the resulting mixture filtered, washed with more ice water and dried 24 Grams of 4-nιtrophenylchloroxιme (4-nιtrophenyl hydroxamoyl chloride) were 5 obtained To 10 grams (0 05 mole) of 4-nιtrophenylchloroxιme were added 150 milliliters of ethanol and a catalytic amount of 4-(N,N-dιmethyl)amιnopyrιdιne 4 0 Grams of 2-amιno- 4-nιtrophenol were added to the mixture The mixture was stirred under nitrogen at room temperature for 90 minutes, at which time another 3 7 grams of 1 -amιno-4-nιtrophenol were 0 added The mixture was then stirred overnight at room temperature under a nitrogen blanket, cooled to 20°C and filtered to yield 2-(p-nιtrophenyl)-5-nιtrobenzoxazole A 7 5-gram portion of the 2-(p-nιtrophenyl)-5-nιtrobenzoxazole was dissolved in 100 milliliters of 1 ,4-dιoxane A 10% palladium-on-carbon catalyst (2 0 grams) was added and the mixture stirred under nitrogen The mixture was heated to 53°C and hydrogen gas was 5 bubbled into the mixture for 6 5 hours The catalyst was then filtered off and the remaining solution added to water The solvent and water were then evaporated off to yield 2-(p- amιnophenyl)-5-amιnobenzoxazole Example 3 Using the general procedure described in Example 2, except that 3- 0 nitrobenzaldehyde was used in replace of the 4-benzaldehyde, 3-nιtrobenzaldoxιme was prepared A 4 98-gram (0 03 mole) portion of the 3-nιtrobenzaldoxιme was combined with 100 milliliters of 1 ,4-dιoxane and 40 milliliters of concentrated HCI x he mixture was cooled to below 5°C and then 47 grams of a 5 25% aqueous solution of sodium hypochlorite (0 033 mole) 5 were added dropwise, keeping the temperature of the mixture at 10°C Then, 50 milliliters of ice water were added and the resulting mixture was filtered, washed with more ice water and dried to produce 3-nιtrophenylchloroxιme (3-nιtrophenyl hydroxamoyl chloride) To 11.5 grams (0.05 mole) of 3-nιtrophenylchloroxιme were added 150 milliliters of ethanol. To the mixture were added 23.1 grams (0.15 mole) of 2-amιno-4-nιtrophenol . The mixture was stirred under nitrogen at 30 C C overnight and filtered to yield 2-(m-nιtrophenyl)-5- nitrobenzoxazole. A 1 1.1-gram portion of the 2-(m-nιtrophenyl)-5-nιtrobenzoxazole was dissolved in 200 milliliters of n-propanoi. A 10% pallaαium-on-carpon catalyst (2.0 grams) was added and the mixture stirred under nitrogen The mixture was heated to 70°C and hydrogen gas was bubbled into the mixture until substantially all the nitro groups have been reduced to primary amine groups, as indicated by liquid chromatography. The catalyst was then filtered off and the remainmg solution added to water. The solvent and water were then evaporated off to yield 2-(m-amιnophenyl)-5-amιnobenzoxazo!e

Claims: CLAIMS 1 A process tor preparing a 2-(aryl)-benz(ox, thi, ιmιd)azole, comprising- (a) contacting an aromatic aldehyde with hydroxylamine under conditions such that an aromatic aldehyde oxime is formed; (b) contacting said aromatic aldehyde oxime with a halogenating agent under conditions such that an aromatic hydroxamoyl halide is formed and (c) contacting the aromatic hydroxamoyl halide with an aromatic amine compound which has a primary amine group ortho to a hydroxyl group, a thiol group or another primary amine group to form a 2-(aryl)-benz(ox, thi, ιmιd)azoie 2 The process of Claim 1 wherein said halogenating agent is Cl 2 , Br 2 or hypochlorous acid or hypobromous acid 3 The process of Claim 2 wherein the halogenating agent is hypochlorous acid which is formed in situ 4 The process of Claim 3 wherein said hypochlorous acid is formed in situ from a mixture of HCI and a peroxysulfate salt or a mixture of sodium hypochlorite and a protic acid 5 The process of Claim 1 wherein neither the aromatic aldehyde nor the aromatic amine compound contains a nitro group and the process further comprises the steps of contacting the 2-(aryl)-benz(ox, thi, ιmιd)azole with a nitrating agent under conditions sufficient to add a nitro group to each of the aromatic ring structures, and then reducing the nitro groups to primary amine groups 6 The process of Claim 5 wherein the aromatic aldehyde has a -CHO group bonded to a pyndinyl, phenyl, anthracyl or naphthyl group 7 The process of Claim 6 wherein the aromatic amine compound is o- aminophenol 8 The process of Claim 1 wherein the aromatic aldehyde is nitro-substituted on an aromatic nucleus 9 The process of Claim 8 wherein the aromatic amine compound is not nitro- substituted and a 2-(nιtroaryl)-benz(ox, thi, ιmιd)azole is formed, and wherein the process further comprises the steps of contacting the 2-(nιtroaryl)-benz(ox, thi, ιmιd)azole with a nitrating agent under conditions sufficient to add a nitro group to the aromatic ring structure fused to the (ox, thi, ιmιd)azole ring, and then reducing the nitro groups to primary amine groups 10 The process of Claim 9 wherein the aromatic aldehyde has a -CHO group bonded to a nitrophenyl, nitroanthracyl or nitronaphthyl group 1 1 The process of Claim 10 wherein the aromatic amine compound is o- aminophenol 12. The process of Claim 1 1 wherein said halogenating agent comprises Cl 2 , Br 2 , hypochlorous acid, or hypobromous acid. 13. The process of Claim 12 wherein the halogenating agent is hypochlorous acid which is formed in situ. 14. The process of Claim 13 wherein said hypochlorous acid is formed in situ from a mixture of HCI and a peroxysulfate salt or a mixture of sodium hypochlorite and a protic acid 15. The process of Claim 8 wherein the aromatic amine compound is nitro- substituted on an aromatic nucleus and a 2-(nιtroaryl)-nιtrobenz(ox, (thi, ιmιd)azole is formed, and wherein the process further comprises reducing the nitro groups to primary amine groups 16- The process of Claim 15 wherein the aromatic aldehyde has a -CHO group bonded to a nitrophenyl, nitroanthracyl or nitronaphthyl group 17. The process of Claim 16 wherein the aromatic amine compound is 2-amιno-4- nitrophenol. 18. The process of Claim 1 1 wherein said halogenating agent comprises Cl 2 , Br 2 , hypochlorous acid or hypobromous acid 19 The process of Claim 18 wherein the halogenating agent is hypochlorous acid which is formed in situ. 20. The process of Claim 19 wherein said hypochlorous acid is formed in situ from a mixture of HCI and a peroxysulfate salt or a mixture of sodium hypochlorite and a protic acid

Inventors: LYSENKO ZENON, LYSENKO, ZENON
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1996
Main classification: C07D263
IPC codes: C07D235, C07D263, C07D277