Method for handling (2-alkyl) acryloyl isocyanate, method for producing (2-alkyl)acryloyl isocyanate, heterocyclic compound, and method for producing heterocyclic compound

Abstract: A method for handling and stabilizing a (2-alkyl)acryloyl isocyanate represented by formula (1) is disclosed, which comprises the steps of: reacting an azomethine compound represented by formula (2) with the (2-alkyl)acryloyl isocyanate to obtain a reaction product and dissolving the reaction product into a solvent to regenerate the (2-alkyl)acryloyl isocyanate; wherein R¹ represents a hydrogen atom or a lower alkyl group, wherein R² represents an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, or an alkynyl group, and R³ and R⁴ each represents a hydrogen atom or a group which does not cause tautomerism with C=N in the formula, provided that at least one of R³ and R⁴ is not a hydrogen atom, and further a method for producing a (2-alkyl)acryloyl isocyanate is disclosed, which comprises the step of: preparing a heterocyclic compound represented by formula (3) and dissolving the heterocyclic compound into a solvent; wherein R¹ represents a hydrogen atom or a lower alkyl group, wherein R⁵ represents a hydrogen atom or a lower alkyl group, R⁶ represents an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, or an alkynyl group, and R⁷ and R⁸ each represents a hydrogen atom or a group in which a carbon atom located in the α-position to carbon atoms constituting a heterocyclic ring does not have a hydrogen atom, provided that at least one of R⁷ and R⁸ is not a hydrogen atom.

Description: The present invention relates to a novel heterocyclic compound, a method for producing the novel heterocyclic compound from an acyl isocyanate compound, thereby stabilizing the acyl isocynate compound, and a method for producing the acyl isocynate compound. Particularly, the present invention relates to a method for producing a heterocyclic compound from a (2-alkyl)acryloyl isocyanate to a method for producing the (2-alkyl)acryloyl isocyanate, and also to the heterocyclic compound. BACKGROUND OF THE INVENTION (2-Alkyl)acryloyl isocyanates represented by acryloyl isocyanate, methacryloyl isocyanate, and the like contain a polymerizable carbon-carbon unsaturated group and an isocyanate group in the same molecule. Since these functional groups react with different mechanisms to participate in various reactions, utilization of (2-alkyl)acryloyl isocyanates in the fields of synthesis chemistry, polymer chemistry, etc. is expected. For example, European Patent Application No. 0177122-A (corresponding to JP-A-60-231644) discloses use of a (2-isocyanate for synthesizing a novel compound represented by formula (4): (wherein R's may be the same or different and each represents a lower alkyl group). (The term "JP-A" as used herein means an "unexamined published Japanese patent application.") Further, European Patent Application No. 0177122-A (corresponding to JP-A-61-17554) discloses use of a (2-alkyl)acryloyl isocyanate for synthesizing a novel compound represented by formula (5): (wherein R represents a lower alkyl group and Z represents an organic group having a tertiary amino group). Both of the novel compounds respectively represented by formulae (4) and (5) have been proved to be useful in the fields of paints and plastics. It is therefore increasingly expected that other useful novel compounds is synthesized from (2-alkyl)acryloyl isocyanates. Although (2-alkyl)acryloyl isocyanates, which are expected to be effectively utilized, are stable compounds which are liquid at ordinary temperature, it is difficult to handle them. Specifically, the (2-alkyl)acryloyl isocyanates are extremely reactive with moisture in air and are thus readily denatured. In addition, the isocyanates have a strong irritating odor and tend to impair the working condition. Because of these, the (2-alkyl)acryloyl isocyanates should be carefully handled using a syringe, etc. SUMMARY OF THE INVENTION An object of the present invention is to facilitate the handling of a (2-alkyl)acryloyl isocyanate by providing a method for the production of a heterocyclic compound, thereby stabilizing the (2-alkyl)acryloyl isocyanate Another object of the present invention is to provide a process for the production of the (2-alkyl)acryloyl isocyanate in a simplified manner. A further object of the present invention is to provide a novel heterocyclic compound. The methods for producing a heterocyclic compound and for producing a (2-alkyl)acryloyl isocyanate according to the present invention are methods for handling and stabilizing a (2-alkyl)acryloyl isocyanate represented by formula (1): (wherein R 1 represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms). This handling comprises the steps of reacting an azomethine compound represented by formula (2) with the (2-alkyl)acryloyl isocyanate of formula (1) to obtain a reaction product represented by formula (3) and dissolving crystals of this reaction product into a solvent to regenerate the (2-alkyl)acryloyl isocyanate; (R 2 represents an alkyl group which may be substituted with a halogen atom or an alkoxy group, or a cycloalkyl group, an aralkyl group, an alkenyl group or an alkynyl group each of which may be substituted with one or more groups selected from an alkyl group, halogen, nitro group, cyano group, alkoxy group and silyl group, and R 3 and R 4 each represents a hydrogen atom or a group in which the carbon atom located in the α-position to the C=N group does not have a hydrogen atom, provided that at least one of R 3 and R 4 is not a hydrogen atom.) (wherein R 1 , R 2 , R 3 , and R 4 are as defined in formulae (1) and (2)). The method for producing a heterocyclic compound according to the present invention represented by formula (3) comprises the steps of reacting an azomethine compound represented by formula (2) with the (2-alkyl)acryloyl isocyanate represented by formula (1) to form a heterocyclic compound represented by formula (3). The method of the present invention for producing a (2-alkyl)acryloyl isocyanate represented by formula (1) comprises the step of dissolving a heterocyclic compound represented by formula (3) into a solvent. DETAILED DESCRIPTION OF THE INVENTION Method for Producing a Heterocyclic Compound In the method for producing a heterocyclic compound of the present invention, a (2-alkyl)acryloyl isocyanate represented by formula (1) is employed. In formula (1), R 1 represents hydrogen or a lower alkyl group. The lower alkyl group herein means an alkyl group having 1 to 5 carbon atoms. This alkyl group may be branched. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, sec-butyl, and pentyl. Especially preferred in the present invention are methacryloyl isocyanate, represented by formula (1) wherein R 1 is methyl, and acryloyl isocyanate, represented by formula (1) wherein R 1 is a hydrogen atom. In this method an azomethine compound represented by formula (2) is reacted with the (2-alkyl)acryloyl isocyanate. In formula (2), R 2 represents an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, or an alkynyl group. The alkyl group preferably has 1 to 18 carbon atoms. The alkyl group may be linear or branched, and may be a primary, secondary, or tertiary alkyl group. Examples of the primary alkyl group include methyl, ethyl, propyl, butyl, isobutyl, hexyl, 3-ethylhexyl, octyl, and octadecyl. Examples of the secondary alkyl group include isopropyl, 1,5-dimethylhexyl, and 1-ethylpropyl. Examples of the tertiary alkyl group include t-butyl and t-octyl. The cycloalkyl group preferably has not more than 18 carbon atoms (particularly 3 to 18 carbon atoms). Examples of such the cycloalkyl groups include cyclohexyl, cyclopentyl, adamantyl, and cyclodecyl. The aralkyl group preferably has not more than 18 carbon atoms (particularly 6 to 18 carbon atoms). Examples of such the aralkyl groups include benzyl, phenylbenzyl, and 4-phenylbenzyl. The alkenyl group preferably has not more than 18 carbon atoms (particularly 3 to 18 carbon atoms). This alkenyl group may be linear or branched, and may contain a cyclic structure. Examples of such the alkenyl groups include allyl, oleyl, and 2-cyclohexenyl. The alkynyl group preferably has not more than 6 carbon atoms (particularly 3 to 6 carbon atoms), and may be linear or branched. Examples of such the alkynyl groups include propargyl. The alkyl group described above may be partly substituted with a halogen or an alkoxy group. The cycloalkyl, aralkyl, alkenyl, and alkynyl groups described above each may be partly substituted with at least one of alkyl group, halogen, nitro group, cyano group, alkoxy group, and silyl group. In formula (2), R 3 and R 4 each represents a hydrogen atom or a group which does not cause tautomerism with C=N in formula (2), that means a group in which the carbon atom located in the α-position to the carbon atom (C) bonded to the N through a double bond does not have a hydrogen atom, provided that at least one of R 3 and R 4 is not a hydrogen atom. Examples of the group in which the α-position carbon does not have a hydrogen atom include aryl groups, e.g., phenyl, p-methylphenyl, p-chlorophenyl, o-ethoxyphenyl, p-nitrophenyl, biphenyl, m-phenoxyphenyl, 2-naphthyl, and 9-anthranyl; heterocyclic groups, e.g., pyridyl, furyl, and 3-thienyl; alkaryl groups, e.g., tolyl and xylyl; and tertiary alkyl groups, e.g., t-butyl and 2,2-dimethylpentenyl. These groups each may be partly substituted with at least one of alkyl group, halogen, nitro group, cyano group, alkoxy group, silyl group, and phenyl group. R 3 and R 4 may be the same or different. Specific examples of the azomethine compound represented by such formula (2) include p-methylbenzylidenebenzylamine, p-methoxybenzylidenebenzylamine, p-chlorobenzylidenebenzylamine, p-phenylbenzylidenebenzylamine, naphthylmethylidenebenzylamine, furylmethylidene-n-butylamine, vinylidenecyclohexylamine, benzylidenecyclohexylamine, benzylidene-n-butylamine, benzylideneoctadecylamine, benzylidenebenzylamine, benzylideneallylamine, benzylidene-t-butylamine, α-phenyl-p-methylbenzylidenebenzylamine, α-phenylbenzylidenecyclohexylamine, α-naphthylbenzylidenebenzylamine, α-p-chlorophenylbenzylidenebenzylamine, α-t-butylbenzylidenebenzylamine, and 2,2-dimethylpropylidenebenzylamine. In reacting the (2-alkyl)acryloyl isocyanate with the azomethine compound described above, the azomethine compound is used in an amount of preferably from 0.5 to 5 equivalents, particularly preferably from 1.0 to 1.5 equivalents, per 1 equivalent of the (2-alkyl)acryloyl isocyanate. The reaction temperature is desirably regulated in the range of from -20 to 50°C. If the reaction temperature is lower than -20°C, the reaction proceeds with difficulty, so that the stabilization treatment is required for a longer time. On the other hand, if the reaction is carried out at a temperature of higher than 50°C, there is a fear that the reaction product may be decomposed to make the attainment of the object impossible. The reaction temperature is particularly preferably a room temperature(e.g., from 10 to 25°C). This reaction (step) may be performed without or using a solvent. In the case of using a solvent, the solvent is not particularly limited in kind as long as it does not adversely influence the reaction of the (2-alkyl)acryloyl isocyanate with the azomethine compound. Solvents having active hydrogen, such as, e.g., alcohols, cannot be used because such the solvents are highly reactive with the (2-alkyl)acryloyl isocyanate. It is necessary that any usable solvent should be sufficiently dehydrated before use, since the (2-alkyl)acryloyl isocyanate is highly reactive with water. Examples of solvents usable in the above reaction include aliphatic hydrocarbons, e.g., hexane and heptane; aromatic hydrocarbons, e.g., benzene and toluene; ethers, e.g., diethyl ether, dibutyl ether, and dioxane; halogenated hydrocarbons, e.g., methylene chloride, ethylene chloride, dichloroethane, dichlorobenzene, chloroform, and carbon tetrachloride; and ketones, e.g., methyl ethyl ketone, methyl isobutyl ketone, and acetone. The reaction described above is completed earlier by precipitating the resulting heterocyclic compound as crystals (described later). The precipitation of the heterocyclic compound as crystals is accelerated by conducting the reaction using a nonpolar solvent, in particular, a nonpolar solvent having a dielectric constant of less than 5. Examples of the solvent having a dielectric constant of less than 5 include aliphatic hydrocarbons, e.g., hexane and heptane; aromatic hydrocarbons, e.g., benzene and toluene; and ethers, e.g., diethyl ether, dibutyl ether, and dioxane. The reaction described above yields crystals. These crystals consist of a heterocyclic compound represented by formula (3). In this heterocyclic compound, R 1 , R 2 , R 3 , and R 4 , respectively, are as defined in formulae (1) and (2) described above. The (2-alkyl)acryloyl isocyanate is stabilized by being converted into such the heterocyclic compound. This heterocyclic compound can be easily isolated by filtration. In filtration, the reaction system is preferably cooled to -20°C or lower; this cooling brings about an increased recovery. The method described above can be utilized as a method for stabilizing the (2-alkyl)acryloyl isocyanate. Namely, a (2-alkyl)acryloyl isocyanate is stabilized by being converted into a stable heterocyclic compound. This stabilization can be easily accomplished by merely mixing the (2-alkyl)acryloyl isocyanate with the azomethine compound described above. The (2-alkyl)acryloyl isocyanate thus-stabilized can be regenerated by merely dissolving the heterocyclic compound formed by the stabilization into a solvent. This method is therefore effective in storing a (2-alkyl)acryloyl isocyanate over a prolonged time period or in transporting the same. Method for Producing (2-alkyl)acryloyl Isocyanate In the method for producing a (2-alkyl)acryloyl isocyanate of the present invention, the (2-alkyl)acryloyl isocyanate is regenerated from the heterocyclic compound of the general formula (3). In this method, crystals of the heterocyclic compound are dissolved into a solvent in which the crystals are soluble. Usable solvents include halogenated hydrocarbons (e.g., chloroform); esters (e.g., ethyl acetate and dimethyl carbonate); ketones (e.g., methyl isobutyl ketone); and amides (e.g., N-methylpyrrolidone). Especially preferred are polar solvents having a dielectric constant of 5 or higher. Upon dissolution of crystals of the heterocyclic compound into a solvent, the heterocyclic compound dissociates into the (2-alkyl)acryloyl isocyanate and the azomethine compound both used as starting compounds. This dissolution is desirably conducted at a room temperature or at a higher temperature of 100°C or less. If the temperature for dissolution is lower than room temperature, the heterocyclic compound is dissociated with difficulty, resulting in a decreased degree of regeneration of the (2-alkyl)acryloyl isocyanate. On the other hand, if the temperature for dissolution is too high, there is a fear that the (2-alkyl)acryloyl isocyanate regenerated through dissociation may be subjected to a side reaction. The particularly preferred dissolution temperature is from 40 to 60°C. The (2-alkyl)acryloyl isocyanate thus-obtained by dissolving the heterocyclic compound into a solvent can be used as it is for a subsequent synthesis reaction. For example, by using a solvent containing an active hydrogen compound (e.g., an alcohol), the (2-alkyl)acryloyl isocyanate can be recovered as an adduct of the active hydrogen compound. It is also possible to isolate the (2-alkyl)-acryloyl isocyanate by a separation technique (e.g., distillation), before the isocyanate is used in a synthesis reaction. Consequently, according to the handling method comprising the first and second steps described above, the (2-alkyl)acryloyl isocyanate can be handled easily as compared with the case in which the isocyanate is directly used as it is. By the method described above a (2-alkyl)acryloyl isocyanate can be extremely easily produced by merely dissolving the heterocyclic compound described above into a solvent. The heterocyclic compound for use in this production method may be the heterocyclic compound produced in the method described above, or may be a heterocyclic compound synthesized by another chemical method. Heterocyclic Compound The heterocyclic compound of the formula (3) described above is a novel heterocyclic compound provided first according to the present invention. This compound is a solid having a melting point and is thermally stable. It is stable also to moisture. Furthermore, the novel heterocyclic compound has a low vapor pressure and is less irritating. Since the heterocyclic compound has a polymerizable double bond, it is expected to be used as a material for producing a polymer for use of paints, adhesives, plastics, etc. Furthermore, since the carbon-carbon double bond contained in this heterocyclic compound is highly reactive, the heterocyclic compound is also expected to be used as an intermediate for the synthesis of fine-chemical products, e.g., medicines and agricultural chemicals (i.e., pesticides). The present invention will be explained below in more detail by reference to the following Examples, but the invention should not be construed as being limited thereto. EXAMPLE 1 The azomethine compound (1.7 g: 9.0 mmol) shown in Table 1 was added in a nitrogen stream to a solution of methacryloyl isocyanate (1.0 g: 9.0 mmol), represented by the following structural formula (6), in dry benzene (10 ml). The obtained mixture was stirred at 20°C. A white precipitate was generated after 20 minutes, but stirring was further continued thereafter. After the reaction was performed over 180 minutes in total, the white precipitate yielded was separated by filtration to obtain colorless needles. The filtrate was concentrated, and the resulting solid was washed with diethyl ether to further obtain colorless needles. The yield of all these colorless needles obtained was 44%. The crystals obtained were measured with respect to melting point, IR spectrum, and NMR spectrum. The results are shown in Table 2 below. As is apparent from the results in Table 2, the crystals obtained were ascertained to be the novel compound represented by the following structural formula (7). EXAMPLE 2 Using the same methacryloyl isocyanate (1.0 g: 9.0 mmol) as in Example 1, a crystal was obtained in the same manner and under the same conditions as in Example 1, except that the azomethine compound (1.96 g: 9.0 mmol) was changed to those shown in Table 1. The yield of the crystal was 54%. The crystals obtained were measured with respect to melting point, IR spectrum, and NMR spectrum. The results are shown in Table 3 below. As is apparent from the results in Table 3, the crystals obtained were ascertained to be the novel compound represented by the following structural formula (8). EXAMPLES 3 TO 8 The same procedure as in Example 1 was carried out, except that the azomethine compound and the reaction conditions were changed as shown in Table 1 and Table 4, respectively. Thus, crystals of heterocyclic compounds were obtained. The structural formulae and analytical data for the heterocyclic compounds obtained are shown in Table 5 and Table 6, respectively. Example Methacryloyl isocyanate g (mmol) Azomethine compound g (mmol) Solvent Temperature (°C) Time (min) 3 1.0 (9.0) 1.0 (5.1) benzene 20 200 4 1.0 (9.0) 1.0 (4.8) benzene 20 75 5 1.0 (9.0) 1.0 (4.3) benzene 20 40 6 1.0 (9.0) 1.0 (6.2) benzene 20 180 7 1.1 (10.0) 1.7 (9.0) diethyl ether 20 60 8 1.1 (10.0) 1.7 (9.0) diethyl ether 20 60 9 1.0 (9.0) 1.0 (4.4) benzene 20 180 Example Yield (%) Melting point (°C) IR (cm -1 ) 3 72 74-75 1669 (C=O) 1634 (C=N) 4 78 65-66 1671 (C=O) 1636 (C=N) 5 97 67-68 1673 (C=O) 1634 (C=N) 6 44 68-69 1667 (C=O) 1640 (C=N) 7 99 69-71 1671 (C=O) 1634 (C=N) 8 89 34-35 1671 (C=O) 1636 (C=N) 9 68 132-134 1673 (C=O) 1640 (C=N) EXAMPLES 9 TO 11 Deuterated chloroform was introduced into a sample tube for measurement of NMR spectrum. Thereto was added the heterocyclic compound represented by the following structural formula (9). Measurement of NMR spectrum was then carried out under the conditions shown in Table 7 to determine the degree of regeneration of methacryloyl isocyanate. The results obtained are shown in Table 7. Example Conditions Degree of regeneration (%) Solvent Temperature (°C) Time 9 deuterated chloroform 28 instant 33 10 deuterated chloroform 48 instant 50 11 deuterated chloroform 60 instant 75 EXAMPLES 12 TO 14 The degree of regeneration of methacryloyl isocyanate was determined in the same manner as in Examples 9 to 11, except that the heterocyclic compound was changed to that represented by the following structural formula (10). The results obtained are shown in Table 8. Example Conditions Degree of regeneration (%) Solvent Temperature (°C) Time 12 deuterated chloroform 28 instant 33 13 deuterated chloroform 45 instant 50 14 deuterated chloroform 60 instant 75 EXAMPLES 15 TO 17 The degree of regeneration of methacryloyl isocyanate was determined in the same manner as in Examples 9 to 11, except that the heterocyclic compound was changed to that represented by the following structural formula (11). The results obtained are shown in Table 9. Example Conditions Degree of regeneration (%) Solvent Temperature (°C) Time 15 deuterated chloroform 28 instant 44 16 deuterated chloroform 45 instant 62 17 deuterated chloroform 60 instant 75 EXAMPLES 18 TO 20 The degree of regeneration of methacryloyl isocyanate was determined in the same manner as in Examples 9 to 11, except that the heterocyclic compound was changed to that represented by the following structural formula (12). The results obtained are shown in Table 10. Example Conditions Degree of regeneration (%) Solvent Temperature (°C) Time 18 deuterated chloroform 28 instant 44 19 deuterated chloroform 45 instant 56 20 deuterated chloroform 60 instant 76 According to the method of the present invention for producing a (2-alkyl)acryloyl isocyanate, the (2-alkyl)-acryloyl isocyanate can be obtained extremely easily by merely dissolving the stable heterocyclic compound into a solvent. According to the present invention, a novel heterocyclic compound which is useful in the fields of synthesis chemistry and polymer chemistry can be provided. According to the method of the present invention for producing a novel heterocyclic compound, the heterocyclic compound which is useful in the fields of synthesis chemistry and polymer chemistry can be produced.

Claims: A heterocyclic compound of the general formula (3) wherein R 1 represents a hydrogen atom or an alkyl group having 1-5 carbon atoms, R 2 represents an alkyl group which may be substituted with a halogen atom or an alkoxy group, or a cycloalkyl group, an aralkyl group, an alkenyl group or an alkynyl group each of which may be substituted with one or more groups selected from an alkyl group, halogen, nitro group, cyano group, alkoxy group and silyl group, and R 3 and R 4 each represents a hydrogen atom or a group in which the carbon atom located in the α-position to the carbon atom constituting the heterocyclic ring does not have a hydrogen atom, provided that at least one of R 3 and R 4 is not a hydrogen atom. A method for producing a heterocyclic compound represented by formula (3) as defined in claim 1, which comprises the steps of reacting a (2-alkyl)acryloyl isocyanate of the general formula (1) wherein R 1 is as defined in formula (3), with an azomethine compound of the general formula (2) wherein R 2 is as defined in formula (3); and R 3 and R 4 are as defined in formula (3) and do not cause tautomerism with C=N in the formula, provided that at least one of R 3 and R 4 is not a hydrogen atom. The method according to claim 2, wherein an amount of the azomethine compound reacted is from 0.5 to 5 equivalents to the (2-alkyl)acryloyl isocyanate. The method according to claim 2, wherein the reaction between the (2-alkyl)acryloyl isocyanate and the azomethine compound is conducted at a temperature of from -20 to 50°C. The method according to claim 2, wherein the reaction between the (2-alkyl)acryloyl isocyanate and the azomethine compound is conducted in a nonpolar solvent having a dielectric constant of less than 5. A method for producing a (2-alkyl)acryloyl isocyanate represented by formula (1), which comprises the step of dissolving a heterocyclic compound of the general formula (3) as defined in claim 1 into a solvent. The method according to claim 6, wherein the solvent into which the heterocyclic compound is dissolved is a polar solvent having a dielectric constant of 5 or more.

Inventors: HATTA TAIZO, TSUBONIWA NORIYUKI, TSUGE OTOHIKO, URANO SATOSHI, HATTA, TAIZO, TSUBONIWA, NORIYUKI, TSUGE, OTOHIKO, URANO, SATOSHI
Applicants: NIPPON PAINT CO LTD, NIPPON PAINT CO., LTD.
Application year: 1995
Main classification: C07C265
IPC codes: C07D273, C07D413, C07C263