METHOD OF PRODUCING N,N'-DIAZOLE COMPOUNDS

Abstract: Describes a method of producing N,N'-diazole compounds, e.g. N,N'-carbonyldiimidazole, by reacting in an inert solvent, e.g., toluene, a 1-unsubstituted 1H-azole compound, e.g., 1H-imidazole, and a dihalide compound, e.g., phosgene, in the presence of an organic base, e.g., a tertiary amine such as tri(n-butyl)amine. The molar ratio of the 1-unsubstituted 1H-azole compound to the dihalide compound may range from 1.7:1 to 2.3:1. The organic base: 1-unsubstituted 1H-azole compound molar ratio is 1:1 when the molar ratio of the 1-unsubstituted 1H-azole compound to the dihalide compound is less than 2:1. The organic base has a basicity greater than that of the 1-unsubstituted 1H-azole compound, and along with its hydrohalide salt is soluble in the inert solvent.

Description: METHOD OF PRODUCING N,N' -DIAZOLE COMPOUNDS DESCRIPTION OF THE INVENTION The present invention relates to a method of producing N,N'-diazole compounds selected from the group consisting of N,N' -carbonyldiazole, N,N-carbonothioicdiazole, and N,N'- thionyldiazole compounds. More particularly, the present invention relates to a method of preparing such N,N'-diazole compounds by reacting a 1-unsubstituted IH-azole compound with a dihalide compound, e.g., phosgene, in the presence of an inert solvent and an organic base, e.g., a tertiary amine. In accordance with an embodiment of the method of the present invention, Che molar ratio of the 1-unsubstituted IH-azole to the dihalide compound need not exceed 2:1. N,N'-diazole compounds prepared in accordance with the present invention have been found to have acceptable color. N,N'-diazole compounds, such as N,N' -carbonyldiazole, N,N' -carbonothioicdiazole and N,N' -thionyldiazole compounds, are useful as reagents for introducing carbonyl, carbonothioic, thionyl or azole groups into other compounds without formation of a hydrohalide acid co-product. They are more convenient to handle and easier to measure than dihalide compounds, such as phosgene. They are useful in reactions involving dehydration, ester formation and isocyanate formation, and as enzyme and protein binding agents. Further, these diazole compounds are also useful as intermediates for synthesizing medicines and agricultural chemicals. For example, U.S. Patent No. 4,237,709 describes the use of N,N'- carbonyldiazole compounds in the preparation of antibiotics and peptides . It is known that N,N' -carbonyldiazole, N,N'- carbonothioicdiazole and N,N ! -thionyldiazole compounds can each typically be produced by a method involving the reaction of a 1-unsubstituted IH-azole compound and a dihalide compound such as, respectively phosgene, carbonothioic dichloride and thionyl chloride, each in a molar ratio of 4:1. See for example, . Forest, Newer Methods of Preparative Organic Chemistry, Volume V, Academic Press, New York (1968) pages 61 - 108. For example, in the case of N,N' -carbonyldiazole compounds, and more specifically N,N' -carbonyldiimidazole, such a prior art method may be represented by the following general scheme I. General Scheme I 4 χ Solvent In the above general scheme I, twice as many moles of the 1- unsubstituted IH-azole compound are used relative to the number of moles of the desired N,N' -carbonyldiazole compound produced. An excess of the 1-unsubstituted IH-azole compound is required to form a salt with the co-product hydrochloric acid generated in the reaction. Further, in general scheme I the N,N' -carbonyldiazole compound and 1-unsubstituted IH-azole hydrochloride salt compound precipitate together out of solution at the same time, thus requiring the separation of two intimately mixed solids. Such a separation can be a multi-step process requiring extra time and materials. The method represented by general scheme I can be expensive in that: (a) only half of the 1-unsubstituted 1H- azole compound present at the beginning of the reaction is used to form the desired N,N' -carbonyldiazole; and (b) the separation of the precipitated N,N' -carbonyldiazole compound from the precipitated 1-unsubstituted IH-azole hydrohalide salt is typically a multi-step process requiring additional time and materials. General scheme I is applicative also to the production of N,N' -carbonothioicdiimidiazole and N,N'- thionyldimidiazole compounds if the appropriate dihalide compound, e.g., carbonothioic dichloride or thionyl chloride, is substituted respectively for phosgene. United States Patents 3,991,071, 4,080,462 and 4,154,945 disclose a method of preparing carbonylbisimidazole which includes reacting, in an inert solvent, phosgene and IH- imidazole in the presence of an acid-binding agent. The acid- binding agent is described as being a tertiary amine such as triethylamine, pyridine or excess imidazole . Preferred levels of the acid-binding agent and molar ratios of the acid-binding agent to the IH-imidazole are not disclosed in United States Patents 3,991,071, 4,080,462 or 4,154,945. United States Patent 5,552,554 discloses a process of preparing a carbonylating agent, such as N,N'- carbonyldiimidazole or N,N' -carbonyldi (1, 2, 4-triazole) , in- situ by reacting, in the presence of a hydroxyl functional ester and an inert solvent, phosgene and one of IH-imidazole or lH-l,2,4-triazole and an organic base selected from the group consisting of trialkylamine, pyridine, picoline or other substituted pyridine. Preferred molar ratios of the organic base to the IH-imidazole or 1H-1, 2 , 4, -triazole are not disclosed in United States Patent 5,552,554. Examples 2, 5 and 11 in columns 7, 8 and 10 respectively of United States Patent 5,552,554 describe in-situ preparations of N,N'- diazoles wherein the molar ratio of the organic base to 1H- azole compound is in each case greater than 1:1 when the molar ratio of 1-unsubstituted IH-azole compound to phosgene is less than 2:1. It has been observed that discolored, e.g., brown, N,N'- diazole compounds can result from the reaction, in an inert solvent, of a 1-unsubstituted IH-azole compound, e.g., IH- imidazole, and an excess of a dihalide compound, e.g., phosgene, in the presence of an excess of an organic base such as a tertiary amine. The discoloration has been observed to occur in particular when the molar ratio of the organic base to the 1-unsubstituted IH-azole compound is greater than 1:1 while at the same time the molar ratio of the 1-unsubstituted IH-azole compound to the dihalide compound is less than 2:1. It would be desirable to have a method of producing N,N'- diazole compounds having a minimum of discoloration, such as N,N' -carbonyldiazole, N,N' -carbonothioicdiazole and N,N'- thionyldiazole compounds, that is more efficient in terms of the utilization of starting materials, and the process of isolating the desired product. It has now been discovered that N,N' -diazole compounds, such as N,N' -carbonyldiazole compounds, can be produced by reacting a 1-unsubstituted IH-azole compound and a dihalide compound, e.g., phosgene, in a molar ratio that need not exceed 2:1. It has further been discovered that that N,N'- carbonyldiazole compounds produced in accordance with the present invention have a minimum of discoloration. In accordance with the present invention, there is provided a method of producing N,N' -diazole compound selected from the group consisting of N,N' -carbonyldiazole, N,N'- carbonothioicdiazole, and N,N' -thionyldiazole compounds, comprising reacting in an inert solvent and in the presence of an organic base, a 1-unsubstituted IH-azole compound represented by the following general formula I: I wherein X , X and X are independently CR or nitrogen provided that at least one of X 1 , X and X is nitrogen, R 1 and R 2 are independently hydrogen, halogen such as chlorine and bromine, C x - C e alkyl, phenyl, substituted phenyl, or when X 3 is CR 1 together form a fused ring having 4 to 6 carbon atoms inclusive of the two carbon atoms in the 1-unsubstituted IH- azole ring through which R and R are connected; with a dihalide compound selected from a member of the group consisting of: Y—c—Y and Y—s—Y wherein Z is oxygen or sulfur, and Y is independently fluorine, chlorine or bromine, preferably chlorine. The molar ratio of the 1-unsubstituted IH-azole compound to the dihalide compound can vary from 1.7:1 to 2.3:1, preferably from 1.8:1 to 2:1, and more preferably from 1.9:1 to 2:1. The organic base is soluble in the inert solvent, has a basicity greater than that of the 1-unsubstituted IH-azole compound, and forms a hydrohalide salt that is soluble in the inert solvent. The molar ratio of the organic base to the 1- unsubstituted IH-azole compound is 1:1 when the molar ratio of the 1-unsubstituted IH-azole compound to the dihalide compound is less than 2:1. Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used in the specification and claims are to be understood as modified in all instances by the term "about" . DETAILED DESCRIPTION OF THE INVENTION The 1-unsubstituted IH-azole compounds useful in the method of the present invention contain only one secondary amino group which is located in the 1-position of the azole ring, as described in general formula I above. With reference to R and R of general formula I above, by substituted phenyl is meant C - C 6 alkyl substituted phenyl, halogen, e.g., chlorine and bromine, substituted phenyl or C λ - C 6 alkyl and halogen substituted phenyl . The substituents R 1 and R 2 are chosen such that they do not preclude the desired reaction at the 1-position. 1-unsubstituted IH-azole compounds described with reference to general formula I, wherein X 2 is nitrogen, and X 1 and X 3 are each CR 1 , are commonly referred to as 1- unsubstituted lH-imidazoles, or lH-imidazoles . Examples of lH-imidazoles useful in the method of the present invention include, but are not limited to: IH-imidazole; 1H-4- methylimidazole; lH-5-methylimidazole; lH-4-ethyl-5- methylimidazole; 1H-2, 4-dimethylimidazole; 1H-2- phenylimidazole; lH-4-phenylimidazole; 1H-5-phenylimidazole; 1H-2 , 4, 5-triphenylimidazole; lH-2-methyl-4 , 5- diphenylimidazole; lH-4-bromoimidazole; lH-5-bromoimidazole; 1H-4-bromo-5-methylimidazole; lH-4-methyl-5-bromoimidazole; lH-4-bromo-5-phenylimidazole; lH-4-phenyl-5-bromoimidazole; 1H-2 , 4-dibromo-5-methylimidazole; 1H-2 , 5-dibromo-4- methylimidazole; and lH-benzimidazole. 1-unsubstituted IH-azole compounds described with reference to general formula I, wherein X 1 is nitrogen, and X 2 and X 3 are CR 1 are commonly referred to as 1-unsubstituted 1H- pyrazoles or lH-pyrazoles . Examples of lH-pyrazoles useful in the method of the present invention include, but are not limited to: lH-pyrazole; 3 , 5-dimethyl-lH-pyrozole; and 1H- indazole. 1-unsubstituted IH-azole compounds described with reference to general formula I, wherein X 1 and X 2 are both nitrogen and X 3 is CR 1 are commonly referred to as 1- unsubstituted 1H-1, 2, 3-triazoles, or 1H-1, 2 , 3-triazoles . Examples of 1H-1, 2 , 3-triazoles useful in the method of the present invention include, but are not limited to, 1H-1,2,3- triazole and 1H-1, 2 , 3-benzotriazole. 1-unsubstituted IH-azole compounds described with reference to general formula I, wherein X 2 and X 3 are both nitrogen, and X is CR are commonly referred to as 1- unsubstituted 1H-1, 2, 4-triazoles, or 1H-1, 2 , 4-triazoles . Examples of 1H-1, 2 , 4-triazoles useful in the method of the present invention include, but are not limited to, 1H-1,2,4- triazole and lH-5-methyl-l, 2 , 4-triazole . Azole compounds described with reference to general formula I, wherein X , X and X are each nitrogen are commonly referred to as tetrazoles . Such tetrazoles can be represented by two tautomeric forms, IH-tetrazole and 2H-tetrazole. Conversion between the two tautomeric forms is thought to occur through a proton shift. While general formula I is representative of tetrazoles having the 2H-tetrazole tautomeric form, it is also meant to be representative of tetrazoles having the more prevalent IH-tetrazole tautomeric form. Examples of tetrazoles useful in the method of the present invention include, but are not limited to, 1H- tetrazole, lH-5-methyl-tetrazole, lH-5-benzyl-tetrazole and lH-5-phenyl-tetrazole. Preferred 1-unsubstituted IH-azole compounds useful in the method of the present invention include: IH-imidazole; 1H- benzimidazole; lH-pyrazole; lH-indazole; 1H-1, 2 , 3-triazole; 1H-1, 2, 3-benzotriazole; and 1H-1, 2 , 4-triazole . A particularly preferred 1-unsubstituted IH-azole compound is IH-imidazole. A single l-unsubstituted IH-azole compound or a mixture of such compounds may be used as desired. The use of a single 1- unsubstituted IH-azole compound is preferred. In the method of the present invention a l-unsubstituted IH-azole compound is reacted with a dihalide compound, as described above, to form N,N' -carbonyldiazole, N,N- carbonothioicdiazole, or N,N' -thionyldiazole compounds. The molar ratio of the l-unsubstituted IH-azole compound to the dihalide compound may range from 1.7:1 to 2.3:1, preferably from 1.8:1 to 2:1 and more preferably from 1.9:1 to 2:1. Since the desired products of the method of present invention are N,N' -carbonyldiazole, N,N' -carbonothioicdiazole, and N,N'- thionyldiazole compounds, the molar ratio of the 1- unsubstituted IH-azole compound to the dihalide compound is preferably 2:1. However, it is understood by those skilled in the art that in large scale practice, i.e., at the commercial production level, an excess of the dihalide compound, e.g., phosgene, may be used. An excess of the dihalide compound, e.g., phosgene, which can be as high as 20% molar excess, is often present because of the difficulty in accurately measuring such dihalide compounds, which are typically in the gas phase under the reaction conditions employed. The method of the present invention is conducted in the presence of an inert solvent as the reaction medium, which is preferably a solvent for the reactants. By inert, it is meant a solvent which will not interfere or otherwise preclude the reaction between the l-unsubstituted IH-azole and dihalide compound. Classes of inert solvents useful in the practice of the present invention include, but are not limited to, alkanes, aromatic solvents, halogenated solvents, ethers, dioxanes, esters, amides and ureas. Halogenated and aromatic solvents are the preferred classes of inert solvents . More specific examples of inert solvents which may be used include: alkanes such as, hexane, heptane and octane; aromatic solvents, such as toluene, benzene, cumene, mesitylene, propylbenzene, anisole and xylene; halogenated solvents, such as methylene chloride, chlorobenzene, and 1, 2-dichloroethane,- ethers such as, tetrahydrofuran, diethyl ether and 1,2- dimethoxyethane ; dioxanes such as 1, 4-dioxane; esters such as, methyl acetate and ethyl acetate; amides such as, N,N- dimethylformamide and N-methyl-1, 2-pyrrolidine; and ureas such as 1, 3-dimethyl-2-imidaxolidinone. Preferred inert solvents are the organic solvents methylene chloride and toluene. A particularly preferred inert solvent is toluene. In the method of the present invention, the inert solvent is present in an amount sufficient to solubilize the reactants . The method of the present invention is conducted also in the presence of an organic base which has a basicity greater than that of the l-unsubstituted IH-azole compound. The reaction between the l-unsubstituted IH-azole compound and the dihalide compound results in the formation of a hydrohalide acid co-product, e.g., hydrochloric acid in the case of phosgene. By having a basicity greater than that of the 1- unsubstituted IH-azole compound, is meant that the formation of the hydrohalide salt of the organic base is at least thermodynamically favored, and preferably also kinetically favored, over the formation of the l-unsubstituted IH-azole hydrohalide salt. Hydrohalide salt formation which occurs predominantly between the organic base and the hydrohalide acid, allows the l-unsubstituted IH-azole compound to be free to react with the dihalide compound. Any organic base, or mixture of organic bases, which: has a basicity greater than that of the l-unsubstituted IH- azole compound; will not form a covalent bond with the dihalide compound; and together with its hydrohalide salt is soluble in the inert solvent of the reaction mixture, may be used in the practice of the present invention. In the practice of the present invention, the molar ratio of the organic base to the l-unsubstituted IH-azole compound is 1:1, provided the molar ratio of the l-unsubstituted IH- azole compound to the dihalide compound is less than 2:1. When the molar ratio of the l-unsubstituted IH-azole compound to the dihalide compound is less than 2:1, it is necessary that the ratio of the organic base to the l-unsubstituted IH- azole compound not exceed 1:1, so that formation of a discolored N,N' -diazole compound is minimized. Without meaning to be bound by any theory, it is believed that when for example producing N,N' -carbonyldiimidazole in the presence of an excess of phosgene, the excess phosgene reacts with the N,N' -carbonyldiimidazole to form an imidazole carbamoyl chloride which in the presence of excess organic base, e.g., a tertiary amine such as tri (n-butyl) amine, forms as yet uncharacterized dark colored species. The presence of the organic base in a molar ratio of 1:1 with the l-unsubstituted IH-azole compound, also allows for the use of only that amount of l-unsubstituted IH-azole compound that is desired to be incorporated through covalent bond formation into the N,N' -diazole compound product. For example, in producing N, ' -carbonyldiimidazole by the method of the present invention, the ratio of IH-imidazole to the dihalide compound, e.g., phosgene, need not exceed 2:1. Further, in the practice of the present invention when the molar ratio of the l-unsubstituted IH-azole compound to the dihalide compound is equal to 2:1, the molar ratio of the organic base to the l-unsubstituted IH-azole compound may be 1:1 or greater. Since the method of the present invention does not require the presence of an excess of the organic base, it is preferable under these circumstances that the molar ratio of the organic base to the l-unsubstituted IH- azole compound be 1:1. Still further, in the practice of the present invention when the molar ratio of the l-unsubstituted IH-azole compound to the dihalide compound is greater than 2:1, the molar ratio of the organic base to the l-unsubstituted IH-azole compound may be 1:1 or greater, or the molar ratio of the organic base to the dihalide compound may be 2:1 or greater. Since the method of the present invention does not require the presence of an excess of the organic base, it is preferable under these circumstances that the molar ratio of the organic base to the dihalide compound be 2:1. In the practice of the present invention, the organic base and its hydrohalide salt are both soluble in the inert solvent of the reaction mixture. This allows for the facile separation of a N,N' -diazole compound that is substantially free of the hydrohalide salt of the organic base. For example, N,N' -carbonyldiimidazole produced according to the method of the present invention may be isolated from the reaction mixture as a precipitate which is substantially free of the hydrohalide salt of the organic base. Although a small amount of the hydrohalide salt of the organic base may be present in the precipitated N,N' -diazole compound, it is understood by those skilled in the art that the purity of the N,N' -diazole product may be further increased by washing with additional solvent followed by drying. In the practice of the method of the present invention, the organic base is preferably a tertiary amine. Examples of tertiary amines useful in the method of the present invention include: tri (aryl) amines, e.g., wherein each aryl group contains from 6 to 9 carbon atoms, such as triphenylamine and tribenzylamine; tri (alkyl) amines, such as, trimethylamine, triethylamine, N,N-dimethylethylamine, tri (n-propyl) amine, tri (isopropyl) amine, tri (n-butyl) amine, tripentylamine, trihexylamine, trioctylamine, tridecylamine and tridodecylamine. Other useful tertiary amines include 1- methylpyrrolidine, 1-methylpyrrole and 1-methylpiperidine. The tri (alkyl) amines wherein each alkyl group contains from 1 to 12, e.g., 1 to 6, carbon atoms are preferred, with tri (n- butyl) amine being particularly preferred. The l-unsubstituted lH-diazole and dihalide compounds may be charged to the reactor in any order. They may be introduced concurrently or sequentially. The addition may be continuous or intermittent. In a preferred embodiment of the present invention, an appropriate amount of dihalide compound is slowly introduced into a suitable reaction vessel containing appropriate amounts of inert solvent, 1- unsubstituted lH-diazole compound and tertiary amine. The temperature at which the reaction of the method of the present invention is conducted may vary considerably, but ordinarily is at a temperature at which the solvent is liquid, and is in the range of from 15°C to 150°C. A temperature of from 50 °C to 80 °C is preferred, particularly when the inert solvent used is toluene. The pressure at which the reaction of the method of the present invention is conducted is also subject to wide variation. Atmospheric and slightly superatmospheric pressures are generally employed since the reaction is in the liquid phase, although greater or lesser pressures may be used. Preferably the pressure at which the reaction is conducted is atmospheric pressure. The present invention is more particularly described in the following examples, which are intended to be illustrative only, since numerous modifications and variations therein will be apparent to those skilled in the art. Unless otherwise specified, all parts and percentages are by weight. EXAMPLE 1 This example describes the preparation of N,N'- carbonyldiimidazole by a method approximating that represented in General Scheme I, using the following enumerated ingredients . Ingredients Amount in grams | moles Charge f toluene 605.5 | 6.6 IH-imidazole 102.2 | 1.5 Charge 2 phosgene 40.8 | 0.41 Charge 1 was added to a 1 liter four-necked flask fitted with a motor-driven stir blade, a temperature probe and heating mantle (both of which were connected to a temperature feed-back control device) , a phosgene and nitrogen inlet tube, the outlet of which was set above the liquid surface within the flask, and a cold condenser vented to a caustic scrubber. The contents of the flask were then heated to a temperature of about 65°C under a nitrogen purge. With the nitrogen purge turned off, Charge 2 was fed into the flask over a period of 20 to 30 minutes, during which time an exotherm peak of 82°C was observed. At the completion of the addition of Charge 2, the contents of the flask were allowed to cool and degas under a nitrogen purge. At the completion of the degassing phase, the contents of the flask were heated to 80 °C and filtered under nitrogen through a heated 70 to 100 micron glass fritted filter. The collected solids were washed two times each with 173 grams of toluene heated to a temperature of 80°C. The filtrates were collected into a single vessel and allowed to slowly cool to room temperature with stirring under a nitrogen purge, during which time white crystals began precipitating from the filtrate. The precipitate was collected under nitrogen using a 70 to 100 micron glass fritted filter. The collected precipitate was washed four times each with 99 grams of hexane at room temperature to remove excess toluene. The washed precipitate was then dried with slight heating under a nitrogen sweep. In all, 28 grams of dried precipitate were isolated. The percent yield and summary of process steps are tabulated in Table 1. Analysis of the precipitate is detailed in Table 2. EXAMPLE 2 This example describes the preparation of N,N'- carbonyldiimidazole using tri (n-butyl) amine as the organic base, wherein the molar ratio of tri (n-butyl) amine to IH- imidazole is 1.1:1.0 while the molar ratio of IH-imidazole to phosgene is less than 2.0:1.0. Ingredients Amount in grams | moles Charge 1 toluene 250 2.7 tri (n-butyl) amine 103.0 I 0.56 IH-imidazole 34.0 I 0.50 Charge 2 phosgene 25.5 0.26 Charge 1 was added to a 1 liter four-necked flask fitted with a motor-driven stir blade, a temperature probe and heating mantle (both of which were connected to a temperature feed-back control device) , a phosgene and nitrogen inlet tube, the outlet of which was set above the liquid surface within the flask, and a cold condenser vented to a caustic scrubber. The contents of the flask were heated to a temperature of about 65°C to 70°C under a nitrogen purge. With the nitrogen purge turned off, Charge 2 was fed into the flask over a period of about 20 minutes, while maintaining the contents of the flask at a temperature of 70°C to 75°C. At the completion of the addition of Charge 2, the contents of the flask were slowly cooled with constant stirring to and held at room temperature during which time a crystalline precipitate was observed to form. A brown to dark brown colored crystalline precipitate was separated from the contents of the flask under nitrogen by filtration using a 70 to 100 micron glass fritted filter. The collected brown colored precipitate was next washed three times with 150 grams each of toluene followed by two additional washings with 200 grams each of hexane. The washed precipitate, which was still brown to dark brown in color, was dried under a nitrogen sweep. In all, 26.5 grams of dried brown colored precipitate were isolated. The percent yield and summary of process steps are tabulated in Table 1. Analysis of the precipitate is detailed in Table 2. EXAMPLE 3 N,N' -carbonyldiimidazole was prepared in accordance with the method of the present invention using the following enumerated ingredients. Ingredients Amount in grams | moles Charge 1 toluene 173 1.9 tri (n-butyl) amine 92.7 I 0.50 IH-imidazole 34.1 I 0.50 Charge 2 phosgene 26.0 I 0.26 Charge 1 was added to a 500 ml four-necked flask fitted with a motor driven stir blade, a temperature probe and heating mantle (both of which were connected to a temperature feed-back control device) , a phosgene and nitrogen inlet tube the outlet of which was set above the liquid surface within the flask, and a cold condenser vented to a caustic scrubber. The contents of the flask were heated to a temperature of about 65°C to 70°C under a nitrogen purge. With the nitrogen purge turned off, Charge 2 was fed into the flask over a period of from 20 to 30 minutes, while maintaining the contents of the flask at a temperature of 70°C to 75°C. At the completion of the addition of Charge 2, the contents of the flask were cooled with constant stirring to 20°C to 25°C over a period of 1 to 1.5 hours, and then held at that temperature for an additional 30 to 45 minutes. A white crystalline precipitate was separated from the contents of the flask under nitrogen by filtration using a 70 to 100 micron glass fritted filter. The collected precipitate was next washed with 346 grams of toluene and then dried with slight heating under a nitrogen sweep. In all, 32.5 grams of dried precipitate was isolated. The percent yield and summary of process steps are tabulated in Table 1. Analysis of the precipitate is detailed in Table 2. TABLE 1 Results Example Example Example 1 2 3 Test % Yield 3 42% 65% 76% Number of filtrations. 2 1 1 Grams of IH-imidazole used per gram of precipitate collected. 0 3.7 1.3 1.1 The % Yield was determined using the following equation, lOOx (actual grams of precipitate collected / theoretical grams of product) . The number of filtrations required from the completion of the reaction within the flask to the isolation of the final precipitated product. The amount of IH-imidazole added to the reaction at the beginning of the reaction over the grams of precipitate collected. The data of Table 1 shows that the method of the present invention is more efficient than that of the prior art method represented in General Scheme I, in terms of producing N,N'- carbonyldiimidazole. When compared to the prior art method, as represented by Example 1 , the method of the present invention, as represented by Example 3, produces a higher yield of product while using less raw materials, i.e. 1H- imidazole. TABLE 2 Analysis of the Isolated Precipitated Product of Examples 1 , 2 and 3. Results Example Example Example 1 2 3 Test Visual appearance White Brown White % Weight N ST,,NN'' --CCaarrlbonyldiimidazole 98.1\ N.D. 100.7% (by C0 evolution analysis) % Weight N,N' -Carbonyldiimidazole 6 N.D. N.D. 99.5% (by G.C. analysis) Weight Tri (n-butyl) amine e N.A. N.D. 0.08' (by G.C. analysis) % Weight Toluene 6 N.D. N.D. 0.06% (by G.C. analysis] % Weight Ionic Chloride 0.44% N.D. 0.07% (by AgN0 3 titration) " " " N.D. = Not Determined. N.A. = Not Applicable. This analysis is based on the reaction: one mole of N,N'- carbonyldiimidazole + one mole of H 2 0, in the presence of a protic acid, will produce two moles of IH-imidazole and one mole of C0 2 . e G.C. (Gas Chromatograph) . The percent weight of N,N'- carbonyldiimidazole, tri (n-butyl) amine and toluene present in the isolated precipitated product of Examples 1 and 2 were determined here using standard gas chromatographic methods. A Hewlett Packard 5890E gas chromatograph fitted with a column having the following specifications, HP-5 30 M x 0.32 mm i.d. with 0.25 micron film, was used. f The % Weight Ionic Chloride was determined by dissolving a known amount of the isolated precipitated product in water acidified with nitric acid, followed by potentiometric titration of the chloride ion (anion) with AgN0 3 using a silver billet electrode to detect the end point. This method is not specific as to the source of the chloride ion. The data of Table 2 shows that the method of the present invention, as represented by Example 3, results in the production of N,N' -carbonyldiimidazole having a white color which is essentially equivalent to that of the prior art method represented by Example 1. The data of Table 2 also shows the criticality of maintaining the molar ratio of the tertiary amine to IH-imidazole at 1:1 when the molar ratio of IH-imidazole to phosgene is less than 2:1, in comparing Examples 2 and 3. The present invention has been described with reference to specific details of particular embodiments thereof. It is not intended that such details be regarded as limitations upon the scope of the invention except insofar as and to the extent that they are included in the accompanying claims .

Claims: We claim : 1. A method of producing N,N' -diazole compound selected from the group consisting of N,N' -carbonyldiazole, N,N'- carbonothioicdiazole and N,N' -thionyldiazole compounds, comprising reacting in an inert solvent: (a) l-unsubstituted IH-azole compound represented by the following general formula, wherein X 1 , X and X are independently CR 1 or nitrogen provided that at least one of X , X and X is nitrogen; R 1 and R 2 are independently hydrogen, halogen, C - C 6 alkyl, phenyl, substituted phenyl, or when X 3 is CR 1 together form a fused ring having 4 to 6 carbon atoms inclusive of the two carbon atoms in the l-unsubstituted IH-azole ring through which R 1 and R z are connected; and (b) a dihalide compound selected from a member of the group consisting of wherein Z is oxygen or sulfur, and Y is independently fluorine, chlorine or bromine, the molar ratio of said 1- unsubstituted IH-azole compound to said dihalide compound being from 1.7:1 to 2.3:1, in the presence of an organic base that is soluble in said inert solvent and that has a basicity greater than that of said l-unsubstituted IH-azole compound, the molar ratio of said organic base to said l-unsubstituted IH-azole compound being 1:1 when the molar ratio of said 1- unsubstituted IH-azole compound to said dihalide compound is less than 2:1, thereby producing said N,N' -diazole compound and a hydrohalide salt of said organic base, said hydrohalide salt being soluble in said inert solvent. 2. The method of claim 1 wherein when X 3 is CR 1 and R 1 and R together form a fused ring, said fused ring is a benzene ring. 3. The method of claim 1 wherein X 1 and X 3 are CR 1 and X 2 is nitrogen. 4. The method of claim 3 wherein R 1 and R 2 are each hydrogen. 5. The method of claim 1 wherein Y is chlorine or bromine . 6. The method of claim 5 wherein Y is chlorine. 7. The method of claim 6 wherein said dihalide compound is phosgene. 8. The method of claim 1 wherein the molar ratio of said l-unsubstituted IH-azole compound to said dihalide compound is from 1.8:1 to 2:1. 9. The method of claim 8 wherein the molar ratio of said l-unsubstituted IH-azole compound to said dihalide compound is from 1.9:1 to 2:1. 10. The method of claim 1 wherein said organic base is a tertiary amine. 11. The method of claim 10 wherein said organic base is selected from at least one of the group consisting of N,N- dimethylethyl amine, tri (n-propyl) amine, tri (isopropyl) amine and tri (n-butyl) amine. 12. The method of claim 11 wherein said organic base is tri (n-butyl ) amine . 13. The method of claim 1 wherein said inert solvent is selected from the group consisting of aromatic solvents and halogenated solvents . 14. The method of claim 13 wherein said inert solvent is an aromatic solvent. 15. The method of claim 14 wherein said inert solvent is toluene . 16. A method of producing N, N' -carbonyldiazole compounds, comprising reacting in an inert solvent: (a) l-unsubstituted IH-azole compound represented by the following general formula, wherein X 1 , X 2 and X 3 are independently CR 1 or nitrogen provided that at least one of X , X and X 3 is nitrogen; R 1 and R 2 are independently hydrogen, halogen, C x - C 6 alkyl, phenyl, substituted phenyl, or when X 3 is CR 1 together form a fused ring having 4 to 6 carbon atoms inclusive of the two carbon atoms in the l-unsubstituted IH-azole ring through which R and R 2 are connected; and (b) a dihalide compound represented by the following general formula, 0 l| Y—C Y wherein Y is independently fluorine, chlorine or bromine, the molar ratio of said l-unsubstituted IH-azole compound to said dihalide compound being from 1.7:1 to 2.3:1, in the presence of an organic base that is soluble in said inert solvent and that has a basicity greater than that of said l-unsubstituted IH-azole compound, the molar ratio of said organic base to said l-unsubstituted IH-azole compound being 1:1 when the molar ratio of said l-unsubstituted IH-azole compound to said dihalide compound is less than 2:1, thereby producing said N,N' -carbonyldiazole compound and a hydrohalide salt of said organic base, said hydrohalide salt being soluble in said inert solvent . 17. The method of claim 16 wherein when X 3 is CR 1 and R 1 and R 2 together form a fused ring, said fused ring is a benzene ring. 18. The method of claim 16 wherein X 1 and X 3 are CR 1 , X 2 is nitrogen, Y is chlorine, said inert solvent is selected from the group consisting of aromatic solvents and halogenated solvents, and said organic base is a tertiary amine. 19. The method of claim 18 wherein R 1 and R 2 are each hydrogen, said organic base is tri (n-butyl) amine, said inert solvent is an aromatic solvent, and the molar ratio of said 1- unsubstituted IH-azole compound to said dihalide compound is from 1.8:1 to 2:1. 20. The method of claim 19 wherein said inert solvent is toluene, and the molar ratio of said l-unsubstituted IH-azole compound to said dihalide compound is from 1.9:1 to 2:1.

Inventors: DAMLE SURESH B, ESWARAKRISHNAN SEETHA L, TANG ROBERT H, DAMLE, SURESH, B., ESWARAKRISHNAN, SEETHA, L., TANG, ROBERT, H.
Applicants: PPG INDUSTRIES INC, PPG INDUSTRIES, INC.
Application year: 1998
Main classification: C07D233
IPC codes: C07D233, C07D521