PROCESS FOR PRODUCING AZOIMINO ETHERS

Abstract: An azoimino ether, which is an intermediate for prepar­ ing polymerization initiators, can be produced by reacting a hydrazonitrile having a hydrazo group and at least one cyano group in the molecule with chlorine in the presence of a primary alcohol, preferably in a non-aqueous organic sol­ vent.

Description: This invention relates to a process for producing azoimino ethers which are intermediates for the syntheses of azoguanyl compounds, azoamide compounds, azoester compounds and the like useful as polymerization initiators in the production of polymeric compounds. Azoguanyl compounds are useful particularly as a polymerization initiator for use in aqueous solutions, because their mineral acid salts are water-soluble. Azoamide compounds are useful as polymerization initiator effectively usable in the non-salt form. Azoester compounds are useful as polymerization initiator excellent in solubility. Azoimino ethers are intermediates of these compounds useful as polymerization initiator. Hitherto, azoimino ethers have been produced by reacting the corresponding azonitrile compound in the presence of hydrogen chloride in an alcoholic solvent, as mentioned in U.S. Patent No. 2,599,299. This process, however, is disadvantageous from the industrial point of view in that the progress of the reaction often becomes rapid and uncontrollable. On the other hand, as an improvement capable of solving the above-mentioned problem, the process mentioned in Japanese Patent Examined Publication No. 2,230/83 can be referred to. This process comprises reacting an azonitrile with an alcohol in the presence of hydrogen chloride gas in a solvent into which hydrogen chloride gas has a low solubility. According to this process, no rapid reaction takes place and the reaction is quite easy to control. Further, it is economical because it consumes only nearly theoretical amount of hydrogen chloride. Thus, it can be said to be an industrially quite advantageous production process of azoimino ethers. European Published Patent application number 80275 teaches reaction of an azonitrile with an alcohol in the presence of hydrogen chloride to produce an azoiminoether, but requires the use of a special ether solvent. French Patent number 2054248 describes the production of azobisvaleronitrile by a two-step process, first reacting a ketone, hydrogen cyanide or an alkali metal cyanide and hydrazine or a derivative thereof in an aqueous medium and then oxidizing the product. At any rate, however, these prior production processes of imino ethers which comprises reacting an azonitrile with an alcohol in the presence of hydrogen chloride gas (including the above-mentioned improvement) use expensive azonitrile and expensive hydrogen chloride gas as the starting materials, and therefore the produced imino ether is naturally expensive and there is a limitation in the cost down of the process. Accordingly, these processes cannot be said to be industrially satisfactory. Thus, it has been desired earnestly to develop a new industrial process capable of giving imino ether less expensively. An object of the invention is to overcome the above-mentioned disadvantages of the prior art processes and to provide an industrially quite practicable production process of azoimino ethers by which azoimino ethers can be produced less expensive than ever without any rapid reaction but with a very easily controllable reaction. The present invention provides a process for producing an azoimino ether having an azo group (-N=N-) and at least one imino ether group in its molecule which comprises reacting a hydrazonitrile having a hydrazo group and at least one cyano group (-CN) in its molecule with chlorine in the presence of an alcohol capable of converting the cyano group to an imino ether in the presence of hydrogen chloride. Accordingly, the present invention provides a process for producing an azoimino ether having an azo group and at least one imino ether group in the molecule, which comprises reacting a hydrazonitrile having a hydrazo group and at least one cyano group in the molecule with chlorine in the presence of an alcohol which can carry out iminoetherification of the cyano group in the presence of hydrogen chloride in a non-aqueous solvent select from aromatic hydrocarbons and halogenated hydrocarbons. In the prior processes, the starting azonitrile compound has been produced generally by the halogen oxidation of hydrazonitrile compound, and the hydrogen halide formed as by-product of the reaction has been disposed because it is difficult to isolate. However, this is too wasteful. If the halogen oxidation of hydrazonitrile compound and the imino-etherification of azonitrile compound are carried out in one pot and one step, the cost of the process will be reduced owing to the simplification of process and effective utilization of by-product. Based on this expectation, the present inventors have conducted earnest studies to accomplish the present invention. The hydrazonitrile used as a starting material in the invention has a hydrazo group and at least one cyano group (-CN) in its molecule. Said hydrazonitrile may be any of symmetric hydrazonitrile and asymmetric hydrazonitrile. As examples of such hydrazonitriles, those of the following formula can be referred to: wherein R¹, R², R³ and R⁴ independently represent an alkyl group preferably having 1 to 5 carbon atoms; a substituted alkyl group such as hydroxyalkyl, alkoxyalkyl, haloalkyl; a cycloalkyl group preferably having 3 to 6 carbon atoms; an aralkyl group such as benzyl, phenethyl; a substituted aralkyl group having one or more alkyl groups, alkoxy groups, hydroxy groups, halogen atoms as its substituent; an aryl group such as phenyl, naphthyl; and a substituted aryl group having one or more alkyl groups, alkoxy groups, hydroxy groups, halogen atoms as its substituent; and at least one of combinations of R¹ - R² and R³ - R⁴ may form an aliphatic ring. Concrete examples of said hydrazonitrile include 2,2'-hydrazobis(2-methylpropionitrile), 2,2'-hydrazobis-(2-methylbutyronitrile), 2,2'-hydrazobis(2,4-dimethylvaleronitrile), 2,2'-hydrazobis(2-methylhexylonitrile), 2,2'-hydrazobis(2-cyclopropylpropionitrile), 2,2'-hydrazobis(2-phenylpropionitrile), 2-methyl-2-phenylhydrazinopropionitrile, 1,1'-hydrazobis(1-cyanocyclohexane), As said alcohol capable of converting a cyano group (-CN) to an imino ether group in the presence of hydrogen chloride, primary alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, isopropanol, n-butanol can be referred to, for example. Preferably, these alcohols are used in a nearly anhydrous state or in the state having as low a water content as possible. As for the amount of said alcohol, an amount ranging from the theoretical amount required for the iminoetherification to an amount 1.2 times as much as the theoretical amount is usually enough for the purpose. As for the amount of the chlorine used in the invention, an amount ranging from the theoretical amount to a somewhat excessive amount is enough for the purpose. The reaction temperature is somewhat dependent on the kind of azonitrile used. However, the reaction temperature is usually 10°C to 40°C, preferably 20°C to 35°C, and more preferably 25°C to 30°C. The time of reaction is naturally dependent on the kind of azonitrile used and the reaction temperature adopted. If a reaction temperature of 25°C to 30°C is employed, the reaction time is usually about 4 to 24 hours. According to the invention, hydrazo group is converted to azo group (-N=N-) and cyano group (-CN) is converted to imino ether group in one pot and one step. The one-pot one-step reaction of the invention is usually carried out in a non-aqueous system in the presence of a solvent conventionally used in halogen oxidation and iminoetherification such as aromatic hydrocarbon (e.g. benzene, toluene, halogenated hydrocarbon (e.g. dichloromethane, dichloroethane, chloroform, carbon tetrachloride, and some others. That is to say, carrying out the reaction in a non-aqueous system is a preferable condition of the invention, and it is advisable to avoid the existence of water as possible. The reaction of the invention itself is carried out under conditions capable of satisfying the conventional conditions of halogen oxidation and the conditions of iminoetherification. For example in the reaction of 2,2'-hydrazobis(2-methylpropionitrile), 2,2'-hydrazobis-(2-methylpropionitrile) and an amount, ranging from the theoretical amount to 1.2 times the theoretical amount, of alcohol are added to the above-mentioned non-aqueous organic solvent, and an amount, ranging from the theoretical amount to a somewhat excessive amount, of chlorine gas is introduced thereinto at a temperature at which the reaction can progress effectively and the formed 2,2'-azobis(1-imino-1-methoxy-2-methylpropane)·dihydrochloride does not decompose (usually 10 to 40°C, preferably 20 to 35°C, more preferably 25 to 30°C). The introduction of chlorine gas is usually carried out while cooling and stirring the system. If a reaction temperature of, for example, 25°C to 30°C is employed, the reaction time is usually about 4 to 12 hours. As the result of the reaction, the formed azoimino ether is obtained in the form of a HCl-addition salt thereof. If desired, the hydrogen chloride can be removed from the product by a usual procedure. The reaction product can be isolated and purified by a usual method. The azoimino ether thus obtained is represented by the following formula: wherein R¹, R², R³ and R⁴ are as defined above; and R represents a lower alkyl group preferably having 1 to 4 carbon atoms. According to the process of the invention, no rapid reaction takes place and the reaction is easy to control. The azoimino ether obtained is not inferior in yield and quality to that produced according to the prior art processes. The azoimino ether thus obtained is converted to a compound useful as polymerization initiator and the like. For example, it can be converted to a azoguanyl compound by reacting it with ammonia gas or an amine in an appropriate solvent. Otherwise, it can be converted to an azoester compound by hydrolysis. Otherwise, it can be converted to an azoamide compound by reacting the resulting azoester compound further with ammonia. Referring to the following Examples, the invention will be illustrated in more detail. Example 1 To a mixture consisting of 111 ml of toluene and 11.5 g (0.36 mole) of methanol was added 24.9 g (0.15 mole) of 2,2'-hydrazobis(2-methylpropionitrile). While cooling and stirring the mixture, 11,2 g (0.158 mole) of chlorine gas was introduced thereinto at a temperature of 10 to 25°C. Then, the mixture was reacted at 25 to 30°C for 5 hours and allowed to stand overnight. After the reaction, a crystalline precipitate was collected by filtration and dried to obtain 38.5 g of 2,2'-azobis(1-imino-1-methoxy-2-methylpropane)·dihydrochloride melting at 124°C (decomposition). Example 2 To 312 ml of carbon tetrachloride were added 19.2 g (0.60 mole) of methanol and 40 g (0.24 mole) of 2,2'-hydrazobis(2-methylpropionitrile). While stirring the solution, 18 g (0.51 mole) of chlorine gas was introduced thereto at a temperature of 20 to 25°C with stirring. Subsequently, the resulting mixture was stirred and reacted first at 20 to 25°C for six hours and then at 35 to 40°C for one hour. After allowing the reaction mixture to stand overnight, crystals were collected by filtration and dried to obtain 66.5 g of 2,2'-azobis-(1-imino-1-methoxy-2-methylpropane)·dihydrochloride melting at 125°C (decomposition). As has been mentioned above, the present invention can provide a novel and very effective production process of azoimino ether which is the intermediate for the syntheses of azoguanyl compounds, azoamide compounds and azoester compounds useful as the polymerization initiator in the production of polymeric compounds. The process of the invention exhibits an outstanding effect in that it uses a hydrazonitrile compound, much less expensive than azonitrile compound, as its starting material and gives the corresponding azoimino ether from the hydrazonitrile compound in one pot and one step and in that it effectively utilizes the hydrogen halide formed as by-product when hydrazo group is converted to azo group -N=N- which makes the treatment of waste hydrogen halide unnecessary and thereby greatly reduces the cost to bring about a great merit to commerciallization.

Claims: A process for producing an azoimino ether having an azo group and at least one imino ether group in the molecule, which comprises reacting a hydrazonitrile having a hydrazo group and at least one cyano group in the molecule with chlorine in the presence of an alcohol which can carry out iminoetherification of the cyano group in the presence of hydrogen chloride in a non-aqueous solvent selected from aromatic hydrocarbons and halogenated hydrocarbons. A process according to Claim 1, wherein the reaction is carriedout at a temperature of 10 to 40°C. A process according to Claim 1, wherein the hydrazonitrile is represented by the formula: wherein R¹, R², R³ and R⁴ are independently an alkyl group, a substituted alkyl group, a cycloalkyl group, an aralkyl group, a substituted aralkyl group, an aryl group, or a substituted aryl group; and at least one of combinations of R¹ - R² and R³ - R⁴ may form an aliphatic ring. A process according to Claim 1, wherein the alcohol is a primary alcohol having 1 to 4 carbon atoms. A process according to claim 4, wherein the alcohol is methanol, ethanol, n-propanol, isopropanol, n-butanol, or a mixture thereof. A process according to any one of the preceding claims wherein the non-aqueous solvent is benzene, toluene, dichloromethane, dichloroethane, chloroform, or carbon tetrachloride.

Inventors: ICHIRIKI, KAZUO, NAWA, HIROYOSHI, OKUGAWA, TORU, TANAKA, MOTOAKI
Applicants: WAKO PURE CHEMICAL INDUSTRIES, LTD.
Application year: 1986
Main classification: C07C257
IPC codes: C07C257, C07C67, C07C241