WO2018212162A1 - ジアミノベンゼン化合物の製造方法 - Google Patents
ジアミノベンゼン化合物の製造方法 Download PDFInfo
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- WO2018212162A1 WO2018212162A1 PCT/JP2018/018703 JP2018018703W WO2018212162A1 WO 2018212162 A1 WO2018212162 A1 WO 2018212162A1 JP 2018018703 W JP2018018703 W JP 2018018703W WO 2018212162 A1 WO2018212162 A1 WO 2018212162A1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C227/14—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof
- C07C227/16—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton from compounds containing already amino and carboxyl groups or derivatives thereof by reactions not involving the amino or carboxyl groups
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C229/52—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton
- C07C229/54—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton with amino and carboxyl groups bound to carbon atoms of the same non-condensed six-membered aromatic ring
- C07C229/56—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton with amino and carboxyl groups bound to carbon atoms of the same non-condensed six-membered aromatic ring with amino and carboxyl groups bound in ortho-position
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C229/00—Compounds containing amino and carboxyl groups bound to the same carbon skeleton
- C07C229/52—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton
- C07C229/54—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton with amino and carboxyl groups bound to carbon atoms of the same non-condensed six-membered aromatic ring
- C07C229/60—Compounds containing amino and carboxyl groups bound to the same carbon skeleton having amino and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the same carbon skeleton with amino and carboxyl groups bound to carbon atoms of the same non-condensed six-membered aromatic ring with amino and carboxyl groups bound in meta- or para- positions
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D235/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, condensed with other rings
- C07D235/02—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, condensed with other rings condensed with carbocyclic rings or ring systems
- C07D235/04—Benzimidazoles; Hydrogenated benzimidazoles
- C07D235/24—Benzimidazoles; Hydrogenated benzimidazoles with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached in position 2
- C07D235/26—Oxygen atoms
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/55—Design of synthesis routes, e.g. reducing the use of auxiliary or protecting groups
Definitions
- the present invention relates to a novel process for producing diaminobenzene compounds useful as intermediates for chemical products, drug substances and the like. Further, the present invention relates to a novel method for producing a benzimidazole derivative from the obtained diaminobenzene compound after producing the diaminobenzene compound by the production method.
- Benzimidazole derivatives are very useful as intermediates for chemical products and drug substances.
- R 1 is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a nitro group, or a halogen atom
- R 2 is an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms.
- the benzimidazole derivative represented by the formula (1) has an extremely high industrial utility value as an intermediate of a sultan drug substance such as candesartan cilexetil (see, for example, Patent Documents 1 to 3).
- the benzimidazole derivative represented by the formula (5) is synthesized by the following method. First, the following formula (6)
- R 1 is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a nitro group, or a halogen atom
- R A is a hydrogen atom or a protecting group.
- R 1 and R A have the same meanings as those in the formula (6)
- R A is a tert-butoxycarbonyl group, benzyloxycarbonyl group, fluorenylmethoxycarbonyl group, 2,2,2-trichloroethoxycarbonyl group, formyl group, acetyl group, tosyl group, or nosyl group.
- R A1 this protecting group
- the benzimidazole derivative represented by the above formula (5) is synthesized by reacting the obtained diaminobenzene compound with an ortho ester derivative having a desired group, followed by condensation and cyclization reaction.
- Patent Document 1 In the case of reducing the nitro group of the aminonitrobenzene compound represented by the formula (6), in the prior art, an expensive nickel catalyst (see Patent Document 1) or palladium catalyst (see Patent Document 2) is used. At present, a high tin compound (see Patent Document 3) is used.
- an object of the present invention is to provide a method capable of more easily producing a diaminobenzene compound and a benzimidazole derivative using a cheaper material.
- the present inventors have made extensive studies to solve the above problems. As a result, even when an inexpensive alkali metal salt of dithionite ([S 2 O 2 ] 2 ⁇ ) is used, the reduction reaction of the aminonitrobenzene compound or the N-protected nitrobenzene compound represented by the above formula (6) proceeds. I found out. Furthermore, the diaminobenzene compound obtained by performing the reduction reaction in a reaction solvent containing an aprotic polar solvent (a reaction solvent that may contain water) or in the presence of an alkali metal carbonate. Alternatively, the inventors have found that the purity and yield of the N-protected aminobenzene compound can be increased, and the present invention has been completed.
- R 1 is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a nitro group, or a halogen atom
- n When ⁇ 2, the plurality of R 1 may be the same or different from each other, R A is a hydrogen atom or a protecting group.
- the compound in which R A is a hydrogen atom in the formula (1) may be simply referred to as “aminonitrobenzene compound”.
- the compound in which R A is a protecting group may be simply referred to as “N-protected nitrobenzene compound”.
- aminonitrobenzene compound and “N-protected nitrobenzene compound” are collectively referred to, they may be simply referred to as “nitrobenzene compounds”.
- the compound in which R A is a hydrogen atom in the formula (2) may be simply referred to as “diaminobenzene compound”.
- the compound in which R A is a protecting group may be simply referred to as “N-protected aminobenzene compound”.
- diaminobenzene compound and “N-protected aminobenzene compound” are collectively referred to, they may be simply referred to as “aminobenzene compound”.
- R A represents a tert-butoxycarbonyl group, a benzyloxycarbonyl group, a fluorenylmethoxycarbonyl group, a 2,2,2-trichloroethoxycarbonyl group.
- a protecting group such as a formyl group, an acetyl group, a tosyl group, or a nosyl group may be referred to as “R A1 ”.
- an aminonitrobenzene compound or N-protected nitrobenzene compound represented by the formula (1) and the alkali metal salt of dithionite in a reaction solvent containing an aprotic polar solvent Is preferably brought into contact.
- the amount of water is preferably 1 to 3 mol.
- the decomposition of the alkali metal salt of dithionite is suppressed and the dissolution of the substrate and the reactant is promoted, and the aminobenzene compound The purity and yield can be increased.
- the aminonitrobenzene compound or N-protected nitrobenzene compound represented by the formula (1) is contacted with the alkali metal salt of dithionite in the presence of an alkali metal carbonate. It is preferable. By the presence of the alkali metal carbonate, it is considered that side reactions such as sulfonation of the benzene ring can be suppressed. Further, it is considered that the reaction can be promoted by neutralizing the alkali metal hydrogensulfate or alkali metal hydrogensulfite produced in the reaction. Furthermore, extraction and isolation of the aminobenzene compound can be facilitated.
- the amount of the alkali metal salt of dithionite used is 1 to 5 Mole is preferred.
- the protecting group for R A is a tert-butoxycarbonyl group, a benzyloxycarbonyl group, a fluorenylmethoxycarbonyl group, 2 2,2-trichloroethoxycarbonyl group, 4-nitrobenzyloxycarbonyl group, formyl group, acetyl group, tosyl group, or nosyl group.
- the obtained N-protected aminobenzene compound is brought into contact with an acid, a base, or hydrogen to form a diaminobenzene compound. Is preferred.
- R 2 is an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms
- R 3 is an alkyl group having 1 to 6 carbon atoms and may be the same or different.
- orthoester derivative (Hereinafter sometimes simply referred to as “orthoester derivative”).
- Benzimidazole derivatives (hereinafter sometimes simply referred to as “benzimidazole derivatives”).
- the present invention it is possible to produce a diaminobenzene compound by using an alkali metal salt of dithionite that is cheaper and safer than conventionally used reducing agents.
- an alkali metal salt of dithionite it is easier to isolate and purify the resulting diaminobenzene compound than the conventional method using a palladium catalyst.
- the reaction solvent may contain water. By containing water, the above-mentioned effect is more remarkably exhibited.
- the benzene ring is sulfonated. The generation of converted by-products (polar impurities) can be further suppressed.
- the purity and yield of the resulting diaminobenzene compound can be further increased by using a reaction solvent containing an aprotic polar solvent.
- the N-protected nitrobenzene compound by using the N-protected nitrobenzene compound, it is possible to suppress the formation of a by-product in which the benzene ring is sulfonated (hereinafter, this by-product may be referred to as a “polar impurity”). Further, the obtained N-protected aminobenzene compound has high solubility in a water-insoluble organic solvent. As a result, it is possible to more easily purify the product by washing and extraction.
- Benzimidazole derivative can be easily produced by reacting the obtained diaminobenzene compound with an ortho ester derivative. Since the obtained benzimidazole derivative can be used as an intermediate for various chemical products and drug substances, the industrial utility value of the present invention is very high.
- the present invention is a method for producing the aminobenzene compound by reducing the nitro group of the nitrobenzene compound to an amino group with an alkali metal dithionite.
- the nitrobenzene compound and the alkali metal salt of dithionite may be mixed. In the following, description will be given in order.
- n is an integer of 1 to 4, preferably 1, and R 1 is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or 2 to 6 carbon atoms.
- an alkoxycarbonyl group having 2 to 6 carbon atoms is preferable for use as an intermediate for various substances and drug substances.
- R 1 of the nitrobenzene compound is an alkyl group having 1 to 6 carbon atoms or an alkoxycarbonyl group having 2 to 6 carbon atoms, it can be used as a raw material for candesartan cilexetil.
- R 1 is not particularly limited. Above all, if used as a raw material of candesartan cilexetil, it is preferable that the carbon atoms adjacent to the carbon atom bonded to NHR A group and R 1 is bonded. Therefore, R 1 is preferably a 2-amino-3-nitrobenzene compound or a 2-N-protected amino-3-nitrobenzene compound bonded to the 1st carbon atom.
- R A is a hydrogen atom or a protecting group.
- R A is a hydrogen atom, the process (deprotection reaction) can be simplified.
- R A is a protecting group
- the resulting compound becomes the N-protected aminobenzene compound, and the purity can be easily increased by washing with water or extraction.
- the production of by-products (polar impurities) in which the benzene ring is sulfonated can be suppressed.
- the protecting group include tert-butoxycarbonyl group, benzyloxycarbonyl group, fluorenylmethoxycarbonyl group, 2,2,2-trichloroethoxycarbonyl group, formyl group, acetyl group, tosyl group, or nosyl.
- protecting groups (R A1 ) such as a group.
- R A (R A1 ) is preferably a tert-butoxycarbonyl group.
- the nitrobenzene compound can be produced using a known method.
- the nitro group of the nitrobenzene compound is reduced to an amino group with an alkali metal salt of dithionite.
- the alkali metal salt of dithionite it is cheaper than a conventionally known palladium-based catalyst, and the aminobenzene compound thus obtained can be easily isolated and purified. That is, after completion of the reaction, the alkali metal salt of dithionite is easier to remove than the palladium catalyst.
- the alkali metal is preferably sodium or potassium, and is preferably sodium in terms of easy availability and handling.
- Specific examples of alkali metal salts of dithionite include hydrosulfite sodium and hydrosulfite potassium, with hydrosulfite sodium being preferred.
- alkali metal salts of dithionite can be used. Some commercially available products contain sodium disulfite and potassium carbonate as impurities, but these can also be used in the present invention.
- the alkali metal salt of dithionite is not particularly limited, but one having a purity of 70% by mass to 100% by mass can be used. Among them, an alkali metal salt of dithionite having a purity of 70% by mass or more and 95% by mass or less is easily available industrially and can be easily used in the present invention.
- the amount of alkali metal salt of dithionite is not particularly limited. However, in order to perform the reduction reaction in a relatively short time and facilitate post-treatment, it is preferable to use 1 to 10 mol of an alkali metal salt of dithionite per 1 mol of the nitrobenzene compound. It is more preferable to use 1 to 5 mol, and it is more preferable to use 1 to 4 mol.
- the reduction reaction can proceed only by allowing the alkali metal salt of dithionite to be present in the reaction system.
- an alkali metal carbonate be further present in the reaction system.
- Alkali metal carbonate in addition to the alkali metal salt of dithionite, the presence of an alkali metal carbonate in the reaction system allows the reaction to proceed smoothly and in a short time while suppressing side reactions. There are cases where it is possible. Specifically, it is considered that side reactions such as sulfonation of the benzene ring can be suppressed by the presence of the alkali metal carbonate. Moreover, it is thought that the reaction can be promoted by neutralizing the alkali metal hydrogensulfate or alkali metal hydrogensulfite produced by the reaction. Furthermore, since it is an inorganic salt, it can be easily removed after completion of the reaction, like the alkali metal salt of dithionite.
- this alkali metal carbonate is not an essential component in the present invention, and the reaction (reduction reaction) can proceed without using it.
- the reaction can proceed favorably without using an alkali metal carbonate.
- a base such as ammonia water is used for the neutralization reaction.
- the reaction can be advanced using aqueous ammonia, but the reaction can proceed smoothly and more quickly by using an alkali metal carbonate.
- known alkali metal carbonates can be used. Specific examples include lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, and rubidium carbonate. Of these, potassium carbonate and sodium carbonate are preferable in consideration of cost, reactivity, solubility, and the like.
- the amount used is not particularly limited.
- the amount of the alkali metal carbonate used is preferably 0.5 to 5 moles relative to 1 mole of the nitrobenzene compound, and 1.0 to 3. More preferably, it is 0 mol.
- reaction solvent in order to reduce the nitrobenzene compound with the alkali metal salt of dithionite, both may be sufficiently brought into contact with each other. Therefore, it is preferable to stir and mix the nitrobenzene compound and the alkali metal salt of dithionite in a reaction solvent to sufficiently bring them into contact.
- the reaction solvent to be used is not particularly limited as long as it does not adversely affect the nitrobenzene compound and the alkali metal salt of dithionite and can smoothly proceed the reduction reaction.
- the solubility of the nitrobenzene compound, the alkali metal salt of dithionite, the alkali metal carbonate used as necessary, and the aminobenzene compound obtained water; alcohol; Aprotic polar solvents such as acetone, acetonitrile, dimethylformamide (DMF), dimethylacetamide (DMA), dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP); Aromatic solvents such as toluene; Halogen solvents such as methylene chloride; Etc. These solvents can also be used as a mixed solvent.
- reaction solvent containing an aprotic polar solvent such as DMF, DMA, DMSO and NMP
- DMF aprotic polar solvent
- the reaction solvent preferably contains water.
- the amount of water contained in the reaction solvent is not particularly limited. Among them, in order to increase the solubility of the alkali metal salt of dithionite and suppress the by-product of the polar impurities, the amount of water is 1 to 3 mol relative to 1 mol of the alkali metal salt of dithionite. It is preferable that
- Suitable reaction solvents for use in the present invention include aprotic polar solvents such as DMF, DMA, DMSO, NMP, and mixed solvents containing water.
- aprotic polar solvents such as DMF, DMA, DMSO, NMP
- mixed solvents containing water it is preferable to use a mixed solvent containing DMF and water. Even when this mixed solvent is used, the amount of water is preferably 1 to 3 mol with respect to 1 mol of the alkali metal salt of dithionite.
- the reaction solvent contains an aprotic polar solvent such as DMF, impurities (presumably, by-products (polar impurities) in which the sulfo group generated from the alkali metal salt of dithionite is substituted) are generated. Can be suppressed.
- the amount of dissolution of the alkali metal salt of dithionite can be increased.
- the amount of water in the reaction solvent is too large, for example, if the amount exceeds 3 moles with respect to 1 mole of the alkali metal salt of dithionite, the amount of polar impurities produced tends to increase.
- an aromatic solvent such as toluene can be further blended with a mixed solvent of water and the aprotic polar solvent.
- the mixing ratio of the mixed solvent is preferably 1 to 100 ml of an aprotic polar solvent and 1 to 100 ml of an aromatic solvent with respect to 1 g of the nitrobenzene compound. It is preferable to use ⁇ 25 ml and 2 to 25 ml of aromatic solvent.
- the amount of water tends to increase as the amount of water increases in the reaction solvent, so the amount of water is 1 to 1 mol per 1 mol of the alkali metal salt of dithionite. It is preferable to set it as 3 mol.
- the reaction solvent when used, it is preferable to use such an amount that each component can be sufficiently mixed.
- the reaction solvent is preferably used in an amount of 1 to 250 ml, more preferably 2 to 80 ml, and even more preferably 2 to 25 ml with respect to 1 g of the nitrobenzene compound at a temperature of 23 ° C. .
- the whole quantity of mixed solvent may satisfy the said range.
- the method for introducing the nitrobenzene compound, the alkali metal salt of dithionite, and the alkali metal carbonate to be used, if necessary, into the reaction system (where the reaction is carried out in the reaction vessel) is particularly limited. Is not to be done. That is, any order of introduction may be used. Therefore, a reaction solvent can be charged in the reaction system in advance, and the nitrobenzene compound, the alkali metal salt of dithionite, and the alkali metal carbonate to be used as necessary can be simultaneously introduced into the reaction system.
- the nitrobenzene compound dissolved in the reaction solvent can be introduced into the reaction system as necessary. . Further, both can be introduced into the reaction system by the reverse method. At this time, the alkali metal carbonate used as necessary may be present together with the nitrobenzene compound, may be present together with the alkali metal salt of dithionite, or separately from these. It may be introduced into the reaction system.
- the reaction solvent may contain water and / or an aprotic polar solvent.
- the N-protected nitrobenzene compound when used, it is preferably introduced into the reaction system by the following method. Specifically, an alkali metal dithionite is dispersed (dissolved) in a reaction solvent containing an aprotic polar solvent while stirring in the reaction system, and then dissolved in a reaction solvent containing an aprotic polar solvent. It is preferable that the N-protected nitrobenzene compound is introduced (added) into the reaction system. In this case, water is preferably contained in the reaction solvent in which the N-protected nitrobenzene compound is dissolved.
- reaction temperature suitably with the solvent to be used. Specifically, it is preferably 0 ° C. or higher and the reflux temperature of the reaction solvent containing the nitrobenzene compound, the alkali metal salt of dithionite, and the alkali metal carbonate used as necessary. More specifically, the temperature is preferably 20 ° C. or higher and 150 ° C. or lower, more preferably 50 ° C. or higher and 120 ° C. or lower, and particularly preferably 60 ° C. or higher and 100 ° C. or lower. By carrying out the reaction at this temperature, a higher purity aminobenzene compound can be obtained.
- reaction time may be appropriately determined according to the consumption amount of the nitrobenzene compound, the production amount of the aminonitrobenzene compound, the scale of the reaction, etc., but it may be usually from 30 minutes to 10 hours.
- the reaction atmosphere is not particularly limited, and may be any atmosphere such as an air atmosphere, an inert gas atmosphere, or a hydrogen atmosphere. Among these, in consideration of operability and the like, an air atmosphere is preferable.
- reaction system may be under atmospheric pressure, under pressure, or under reduced pressure. Among these, it is preferable to carry out under atmospheric pressure.
- n is an integer from 1 to 4, preferably 1.
- R 1 and R A are as defined in the above formula (1). ) (A diaminobenzene compound or an N-protected aminobenzene compound).
- R ⁇ 1 > and RA are synonymous with the thing in said Formula (1).
- R 1 is preferably bonded to the carbon atom at the 1-position to become a 2,3-diaminobenzene compound or a 2-N-protected amino-3-aminobenzene compound.
- R A is a hydrogen atom
- the diaminobenzene compound represented by the following formula (2 ′′) can be obtained directly, and therefore the number of steps can be reduced.
- the aminobenzene compound obtained under the above reaction conditions is preferably taken out from the reaction system by the following method. Specifically, it is preferable that a poorly water-soluble organic solvent such as ethyl acetate or methylene chloride is brought into contact with the obtained reaction solution and the aminobenzene compound is extracted with the poorly water-soluble organic solvent. Then, it is preferable to wash
- a poorly water-soluble organic solvent such as ethyl acetate or methylene chloride
- R A1 is a protecting group, specifically, tert-butoxycarbonyl group, benzyloxycarbonyl group, fluorenylmethoxycarbonyl group, 2,2,2-trichloroethoxycarbonyl group, formyl group, acetyl group, tosyl group. It is preferably a group or a nosyl group. N-protected diaminobenzene compounds represented by) are preferred. That is, the following formula (2 ′′)
- R 1 has the same meaning as in formula (1).
- R A is a hydrogen atom in formula (2)
- the N-protected diaminobenzene compound is easily dissolved in the poorly water-soluble organic solvent, and is washed with water. Purity can be easily increased.
- the alkali metal salt of dithionite and the alkali metal carbonate used as necessary are inorganic salts, they can be easily removed by washing with water.
- the aminobenzene compound with high purity can be obtained by washing with water.
- the obtained aminobenzene compound can be further purified by a known method such as recrystallization or column separation.
- R 1 has the same meaning as in formula (1)
- R A1 is a tert-butoxycarbonyl group, a benzyloxycarbonyl group, a fluorenylmethoxycarbonyl group, a 2,2,2-trichloroethoxycarbonyl group, a formyl group, an acetyl group, a tosyl group, or a nosyl group.
- N-protected diaminobenzene compounds represented by This N-protected diaminobenzene compound is easily converted into the following formula (2 ′′)
- R 1 has the same meaning as in formula (1). It can be set as the diaminobenzene compound shown by this. Specifically, the deprotection reaction can be carried out by bringing the N-protected aminobenzene compound into contact with an acid, a base, or hydrogen. Then, the diaminobenzene compound represented by the formula (2 ′′) is obtained. As a suitable compound, R 1 is preferably bonded to the carbon atom at the 1-position to form a 2,3-diaminobenzene compound.
- a known acid can be used as the acid used for removing the protecting group.
- Specific examples include hydrochloric acid, sulfuric acid, hydrobromic acid, methanesulfonic acid and the like. Of these, hydrochloric acid is preferably used from the viewpoint of operability.
- the amount of acid used is not particularly limited, but is preferably from 0.1 to 100 mol, based on 1 mol of the N-protected aminobenzene compound, and is from 1 to 10 mol. More preferably.
- a known base can be used as the base used for removing the protecting group.
- specific examples include inorganic bases such as sodium hydroxide, potassium hydroxide and barium hydroxide, organic bases such as piperidine and morpholine, and salts such as thiophenol potassium salt.
- inorganic bases such as sodium hydroxide, potassium hydroxide and barium hydroxide
- organic bases such as piperidine and morpholine
- salts such as thiophenol potassium salt.
- an inorganic base such as sodium hydroxide or potassium hydroxide, or an organic base such as piperidine.
- the amount of the base used is not particularly limited, but is preferably 0.1 to 100 mol, based on 1 mol of the N-protected aminobenzene compound, and is 1 to 10 mol. More preferably.
- examples of hydrogen used for removing the protecting group include hydrogen gas and a compound that generates hydrogen gas.
- hydrogen it is preferable to use a palladium catalyst.
- hydrogen gas, formic acid, formate, or the like is present in the presence of a palladium catalyst, and the protective group is eliminated by reduction with hydrogen.
- the amount used is not particularly limited, but is 0.001 to 0.5 mol with respect to 1 mol of the N-protected aminobenzene compound. It is preferably 0.01 to 0.1 mol.
- Hydrogen is not particularly limited as long as it is an amount sufficient for reduction.
- formic acid it is preferable to use 1.0 to 10 mol of formic acid with respect to 1 mol of the N-protected aminobenzene compound.
- the solvent to be used is not particularly limited as long as it does not affect the N-protected aminobenzene compound and the acid or base. Specific examples include water, methanol, ethanol, toluene, THF (tetrahydrofuran), dioxane, and the like.
- the order of introducing both into the system is not particularly limited. If necessary, the N-protected aminobenzene compound diluted with a solvent and an acid or a base can be simultaneously introduced into the reaction system. If necessary, one diluted with a solvent can be introduced into the system. The other one previously introduced and diluted with a solvent can be added to the system as necessary. Above all, in order to carry out the deprotection reaction more smoothly, the N-protected aminobenzene compound diluted with a solvent as needed is first introduced into the reaction system, and then diluted with a solvent as necessary. It is preferable to add the acid or base to the system.
- the temperature at which the deprotection reaction is carried out is not particularly limited, and is preferably 0 to 200 ° C, more preferably 5 to 120 ° C.
- the reaction time is not particularly limited, and may be appropriately determined according to the amount of the diaminobenzene compound produced.
- the atmosphere is not particularly limited, and may be any atmosphere such as an air atmosphere or an inert gas atmosphere. Among these, in consideration of operability and the like, an air atmosphere is preferable.
- reaction system may be under atmospheric pressure, under pressure, or under reduced pressure. Among these, it is preferable to carry out under atmospheric pressure.
- the deprotection reaction it is preferable to carry out the deprotection reaction according to the above conditions.
- the acid or base may be removed by washing with water or the like.
- the obtained diaminobenzene compound can be further purified by a known method such as recrystallization and column separation.
- the diaminobenzene compound in which R A in the formula (2) is a hydrogen atom can be obtained by using an aminonitrobenzene compound in which R A in the formula (1) is a hydrogen atom.
- the diaminobenzene compound represented by the formula (2 ′′) can be obtained by performing a deprotection reaction as described above.
- the diaminobenzene compound R A is a hydrogen atom in the formula (2)
- the formula diaminobenzene compound represented by (2 '') is the same compound.
- the ortho ester derivative to be reacted with the diaminobenzene compound is represented by the following formula (3):
- R 2 is an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms.
- R 2 is an alkoxy group
- the compound has four alkoxy groups.
- an ethoxy group is preferable in order to use the obtained benzimidazole derivative as an intermediate of candesartan cilexetil.
- R 3 is an alkyl group having 1 to 6 carbon atoms and may be the same or different.
- Such an ortho ester derivative may be a commercially available product.
- the amount of the orthoester derivative used is not particularly limited, but is 0.5 to 10 mol per mol of the diaminobenzene compound. Preferably, the amount is 0.95 to 2 mol.
- the reaction between the diaminobenzene compound and the orthoester derivative is carried out in the presence of an acid, but this acid is not particularly limited, and includes inorganic acids such as hydrochloric acid and sulfuric acid, formic acid, acetic acid, methanesulfonic acid, An organic acid such as p-toluenesulfonic acid can be used. Among them, it is preferable to use an organic acid such as acetic acid because of easy handling. In this case, the acid used can be used as a reaction solvent.
- the amount of acid used is not particularly limited, but when an acid is used as a reaction solvent, an excess amount may be added. However, considering post-treatment after the reaction, etc., it is preferable to use 0.5 to 10 mL of acid, more preferably 0.5 to 5 mL, per 1 g of the diaminobenzene compound. When an organic solvent is used as the reaction solvent, considering reaction progress, post-treatment, etc., the amount is preferably 0.1 to 10 mol with respect to 1 mol of the diaminobenzene compound, More preferably, it is 3 mol.
- the diaminobenzene compound and the orthoester derivative may be sufficiently brought into contact in an atmosphere in which an acid exists.
- the solvent is preferably ethyl acetate, toluene, tetrahydrofuran (THF) or the like, and particularly preferably toluene. .
- R 1 has the same meaning as in formula (1)
- R 2 has the same meaning as in formula (3). Is obtained.
- the preferred position and substituent of R 1 are also the same as those of the nitrobenzene compound.
- the reaction temperature may be appropriately determined according to the set reaction conditions, but is preferably 0 to 150 ° C, more preferably 10 to 100 ° C, and particularly preferably 10 to 50 ° C. preferable. By satisfy
- the reaction time is sufficient if it is 0.5 to 5 hours.
- the atmosphere is not particularly limited as long as it is in an air atmosphere. Furthermore, the reaction can proceed in any state under reduced pressure, increased pressure, or atmospheric pressure.
- the obtained benzimidazole derivative may be taken out from the reaction system by a known method.
- the benzimidazole derivative can be purified by a known method.
- the obtained benzimidazole derivative can be suitably used as an intermediate (raw material) of a sultan based drug substance such as candesartan cilexetil.
- HPLC high performance liquid chromatography
- Mobile phase A acetonitrile
- Transfer of mobile phase The concentration gradient is controlled by changing the mixing ratio of mobile phases A and B as shown in Table 1 below.
- methyl 2-amino-3-nitrobenzoate (the 2-amino-3-nitrobenzene compound) was about 11.4 minutes, methyl 2,3-diaminobenzoate (the 2,3-diaminobenzene compound). Is about 2.6 minutes, methyl 2-tert-butyloxycarbonylamino-3-nitrobenzoate (the N-protected nitrobenzene compound) is about 19.1 minutes, 2-ethoxy-1H-benzimidazole-7-carboxylic acid A peak of methyl (the benzimidazole derivative) is confirmed at about 4.0 minutes.
- the respective purities of the 2-amino-3-nitrobenzene compound, the N-protected nitrobenzene compound, the 2,3-diaminobenzene compound, and the benzimidazole derivative are all measured under the above conditions. It is the ratio of the peak area value of each compound to the sum of the peak area values (excluding peaks derived from the solvent).
- Example 1 (Example of producing a diaminobenzene compound using an aminonitrobenzene compound) Reaction of the following formula was performed.
- Methyl 2-amino-3-nitrobenzoate (1.0 g, 5.1 mmol; 2-amino-3-nitrobenzene compound), sodium dithionite (purity 80% by mass) (3.33 g, 15.3 mmol ((purity The number of moles of sodium dithionite calculated from: Wako Pure Chemical Industries, alkali metal dithionite), potassium carbonate (1.4 g, 10.2 mmol; alkali metal carbonate carbonate), dimethylformamide (DMF) (4 ml), water (0.367 ml, 20.4 mmol) and toluene (3 ml) in a mixed solvent (reaction solvent) were stirred and mixed at a reaction temperature of 100 ° C. for 4 hours (reaction time).
- a mixed solvent reaction solvent
- methyl 2,3-diaminobenzoate confirmed by HPLC was 94.0%, and it was a polar impurity (presumably a compound having a sulfo group at the 5-position (2,3-diamino-5-sulfo Methyl benzoate)) was 2.2%.
- Analytical values of methyl 2,3-diaminobenzoate were as follows. IR (KBr) 1693 cm ⁇ 1 . 1H-NMR (CDCl3) ⁇ 7.30-7.80 (m, 1H), 6.40-7.10 (m.2H), 1.45 (brs, 2H), 3.85 (s, 3H), 3.40 (brs, 2H).
- Example 2 Example of producing a diaminobenzene compound using an aminonitrobenzene compound
- sodium dithionite purity 80% by mass
- 2.22 g, 10.2 mmol ((number of moles of hydrosulfite sodium calculated from purity); manufactured by Wako Pure Chemical Industries, Ltd., alkali metal of dithionite) Salt
- the reaction time was changed to 5 hours, the same operation as in Example 1.
- the conversion rate was 10%, and polar impurities could not be confirmed.
- Example 3 Example in which an aminonitrobenzene compound was used to produce a diaminobenzene compound
- the reaction solvent was a mixed solvent of DMF (7 ml) and water (0.099 ml, 5.1 mmol).
- the yield of methyl 2,3-diaminobenzoate was 94%.
- the conversion rate was 100%.
- the purity of methyl 2,3-diaminobenzoate confirmed by HPLC was 95.4%, and the polar impurity was 2.5%.
- the analysis result of the obtained methyl 2,3-diaminobenzoate was the same as in Example 1.
- Example 4 Example in which a diaminobenzene compound was produced using an aminonitrobenzene compound
- Example 1 the same operation as in Example 1 was performed except that 7 ml of DMF was used as a reaction solvent.
- the yield of methyl 2,3-diaminobenzoate was 94%.
- the conversion rate was 100%.
- the purity of methyl 2,3-diaminobenzoate confirmed by HPLC was 97.5%, and no polar impurities could be confirmed.
- Example 5 Example of producing a diaminobenzene compound using an aminonitrobenzene compound
- Example 1 the same operation as in Example 1 was performed except that 15 N aqueous ammonia (2.55 ml, NH 3 38.3 mmol) was used instead of potassium carbonate and the reaction solvent.
- the conversion rate was 21.5%.
- polar impurities could not be confirmed.
- Example 6 (Example in which a diaminobenzene compound was produced using an N-protected nitrobenzene compound Reduction reaction and deprotection reaction) Reaction of the following formula was performed. The reduction and deprotection reactions are shown together.
- Methyl 2,3-diaminobenzoate (0.70 g, 4.21 mmol; 2,3-diaminobenzene compound) obtained in Example 4 was dissolved in toluene (1 mL), and tetraethoxymethane (0.81 g, 4.2. 21 mmol; ortho ester derivative) and acetic acid (0.25 g, 4.21 mmol; acid) were sequentially added at room temperature, followed by reaction at 100 ° C. for 2 hours. Water (5 mL) was added to the reaction solution for crystallization and filtration to obtain methyl 2-ethoxy-1H-benzimidazole-7-carboxylate (742 mg, yield: 80%). The purity of methyl 2-ethoxy-1H-benzimidazole-7-carboxylate confirmed by HPLC was 96.7%.
- Example 8 (Example in which a benzimidazole derivative was produced using an N-protected nitrobenzene compound) (Reduction reaction; synthesis of N-protected aminobenzene compound) Weigh methyl 2-tert-butyloxycarbonylamino-3-nitrobenzoate (20 g, 67.50 mmol, N-protected nitrobenzene compound) into a 500 mL four-necked flask equipped with two stirring blades having a diameter of 7.5 cm.
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Abstract
Description
R1は、炭素数1~6のアルキル基、炭素数1~6のアルコキシ基、炭素数2~6のアシルオキシ基、炭素数2~6のアルコキシカルボニル基、ニトロ基、又はハロゲン原子であり、
R2は、炭素数1~6のアルキル基、又は炭素数1~6のアルコキシ基である。)で示されるベンズイミダゾール誘導体は、カンデサルタンシレキセチル等のサルタン系原薬の中間体として、その工業的利用価値が非常に高い(例えば、特許文献1~3参照。)。
R1は、炭素数1~6のアルキル基、炭素数1~6のアルコキシ基、炭素数2~6のアシルオキシ基、炭素数2~6のアルコキシカルボニル基、ニトロ基、又はハロゲン原子あり、
RAは、水素原子、又は保護基である。)で示されるアミノニトロベンゼン化合物又はN-保護ニトロベンゼン化合物のニトロ基を還元し、下記式(7)
R1、およびRAは、前記式(6)におけるものと同義である。)で示されるジアミノベンゼン化合物又はN-保護アミノベンゼン化合物を合成する。この際、RAがtert-ブトキシカルボニル基、ベンジルオキシカルボニル基、フルオレニルメトキシカルボニル基、2,2,2-トリクロロエトキシカルボニル基、ホルミル基、アセチル基、トシル基、又はノシル基等の保護基(以下、この保護基を「RA1」とする場合もある。)であるN-保護アミノベンゼン化合物である場合には、脱保護反応を行い、ジアミノベンゼン化合物とする。
nは1~4の整数であり、
R1は、炭素数1~6のアルキル基、炭素数1~6のアルコキシ基、炭素数2~6のアシルオキシ基、炭素数2~6のアルコキシカルボニル基、ニトロ基、又はハロゲン原子あり、n≧2の場合には、複数個のR1は互いに同一であっても異なっていてもよく、
RAは、水素原子、又は保護基である。)で示されるアミノニトロベンゼン化合物又はN-保護ニトロベンゼン化合物と、
亜ジチオン酸のアルカリ金属塩とを接触させることにより、
下記式(2)
下記式(3)
R2は、炭素数1~6のアルキル基、又は炭素数1~6のアルコキシ基であり、
R3は、炭素数1~6のアルキル基であり、同一であっても、異なる基であってもよい。)で示されるオルトエステル誘導体(以下、単に「オルトエステル誘導体」とする場合もある。)とを反応させることにより、
下記式(4)
さらに、炭酸アルカリ金属塩を反応系内に存在させることにより、ベンゼン環がスルホン化された副生物(極性不純物)の生成をより一層抑制できる。また、非プロトン性極性溶媒を含む反応溶媒を使用することにより、得られるジアミノベンゼン化合物の純度、収率をより高くすることができる。
本発明において、原料として使用するニトロベンゼン化合物は、下記式(1)
本発明においては、亜ジチオン酸のアルカリ金属塩によって、前記ニトロベンゼン化合物のニトロ基をアミノ基に還元する。該亜ジチオン酸のアルカリ金属塩を使用することによって、従来知られていたパラジウム系触媒よりも、安価であって、得られた前記アミノベンゼン化合物を単離精製することが容易となる。すなわち、反応終了後、亜ジチオン酸のアルカリ金属塩は、パラジウム系触媒よりも除去がし易い。
本発明においては、前記亜ジチオン酸のアルカリ金属塩の他、反応系内に炭酸アルカリ金属塩を存在させることにより、反応を円滑に、短時間で、しかも副反応を抑制しつつ進行させることができる場合がある。具体的には、炭酸アルカリ金属塩が存在することにより、ベンゼン環のスルホン化などの副反応を抑制できるものと考えられる。また、反応で生じる硫酸水素アルカリ金属塩または亜硫酸水素アルカリ金属塩を中和し反応を促進させることができると考えられる。さらには、無機塩であるため、前記亜ジチオン酸のアルカリ金属塩と同様に、反応終了後、除去が容易である。なお、この炭酸アルカリ金属塩は、本発明における必須成分ではなく、使用しなくとも反応(還元反応)は進行させることができる。特に、前記N-保護ニトロベンゼン化合物を使用した場合には、炭酸アルカリ金属塩を使用しなくとも、反応を良好に進めることができる。
(反応溶媒)
本発明において、前記ニトロベンゼン化合物を前記亜ジチオン酸のアルカリ金属塩で還元するためには、両者が十分に接触できるようにすればよい。そのため、前記ニトロベンゼン化合物と前記亜ジチオン酸のアルカリ金属塩とを反応溶媒中で攪拌混合して、両者を十分に接触させることが好ましい。
水;
アルコール;
アセトン、アセトニトリル、ジメチルホルムアミド(DMF)、ジメチルアセトアミド(DMA)、ジメチルスルホキシド(DMSO)、N-メチル-2-ピロリドン(NMP)等の非プロトン性極性溶媒;
トルエン等の芳香族溶媒;
塩化メチレン等のハロゲン系溶媒;
などが挙げられる。これら溶媒は、混合溶媒として使用することもできる。
本発明において、前記ニトロベンゼン化合物、亜ジチオン酸のアルカリ金属塩、および必要に応じて使用する炭酸アルカリ金属塩を反応系内(反応容器内等の反応を行う場所)へ導入する方法は、特に制限されるものではない。すなわち、どのような導入順序であってもよい。そのため、予め反応系内に反応溶媒を仕込んでおき、前記ニトロベンゼン化合物、亜ジチオン酸のアルカリ金属塩、および必要に応じて使用する炭酸アルカリ金属塩を同時に該反応系内に導入することもできる。また、必要に応じて反応溶媒で希釈した亜ジチオン酸のアルカリ金属塩を撹拌して分散させた後、必要に応じて反応溶媒に溶解させた前記ニトロベンゼン化合物を反応系内に導入することもできる。さらに、この逆の方法で両者を反応系内に導入することもできる。この時、必要に応じて使用される炭酸アルカリ金属塩は、前記ニトロベンゼン化合物と一緒に存在させてもよいし、亜ジチオン酸のアルカリ金属塩と一緒に存在させてもよいし、これらとは別に反応系内導入してもよい。また、反応溶媒は、水、および/又は非プロトン性極性溶媒を含んでいてもよい。
反応温度は、使用する溶媒によって適宜決定すればよい。具体的には、0℃以上、前記ニトロベンゼン化合物、亜ジチオン酸のアルカリ金属塩、および必要に応じて使用する炭酸アルカリ金属塩を含んだ状態の反応溶媒の還流温度以下であることが好ましい。より具体的には、20℃以上150℃以下であることが好ましく、50℃以上120℃以下であることがより好ましく、60℃以上100℃以下であることが特に好ましい。当該温度で反応を実施することで、より高純度のアミノベンゼン化合物を取得することができる。
本発明において、その他の反応条件は、以下の条件を採用することが好ましい。反応時間は、前記ニトロベンゼン化合物の消費量、前記アミノニトロベンゼン化合物の生成量、反応のスケール等に応じて適宜決定すればよいが、通常、30分間以上10時間以下であればよい。
以上のような条件下で反応を実施することにより、前記ニトロベンゼン化合物を、
下記式(2)
nは1~4の整数であり、好ましくは1であり、
R1、およびRAは、前記式(1)におけるものと同義である。)で示されるアミノベンゼン化合物(ジアミノベンゼン化合物又はN-保護アミノベンゼン化合物)にすることができる。
nは1~4の整数であり、好ましくは1であり、
R1は、前記式(1)におけるものと同義であり、
RA1は、保護基であり、具体的には、tert-ブトキシカルボニル基、ベンジルオキシカルボニル基、フルオレニルメトキシカルボニル基、2,2,2-トリクロロエトキシカルボニル基、ホルミル基、アセチル基、トシル基、又はノシル基であることが好ましい。)で示されるN-保護ジアミノベンゼン化合物が有利となる。すなわち、下記式(2’’)
nは1~4の整数であり、好ましくは1であり、
R1は、前記式(1)におけるものと同義である。)で示されるジアミノベンゼン化合物(式(2)においてRAが水素原子であるとなる化合物)と比較して、該N-保護ジアミノベンゼン化合物は該難水溶性有機溶媒に溶解し易く、水洗により容易に純度を高めることができる。
本発明において、前記N-保護ニトロベンゼン化合物を使用した場合には、下記式(2’)
nは1~4の整数であり、好ましくは1であり、
R1は、前記式(1)におけるものと同義であり、
RA1は、tert-ブトキシカルボニル基、ベンジルオキシカルボニル基、フルオレニルメトキシカルボニル基、2,2,2-トリクロロエトキシカルボニル基、ホルミル基、アセチル基、トシル基、又はノシル基である。)で示されるN-保護ジアミノベンゼン化合物が得られる。このN-保護ジアミノベンゼン化合物は、容易に下記式(2’’)
nは1~4の整数であり、好ましくは1であり、
R1は、前記式(1)におけるものと同義である。)で示されるジアミノベンゼン化合物とすることができる。具体的には、前記N-保護アミノベンゼン化合物と、酸、塩基、又は水素とを接触させることにより、脱保護反応を実施することができる。そして、前記式(2’’)で示されるジアミノベンゼン化合物となる。好適な化合物としては、R1が1位の炭素原子と結合し、2,3-ジアミノベンゼン化合物となることが好ましい。
前記式(2)のRAが水素原子であるジアミノベンゼン化合物は、前記式(1)のRAが水素原子であるアミノニトロベンゼン化合物を使用することで得られる。また、前記式(2’’)で示されるジアミノベンゼン化合物は、前記の通り、脱保護反応を実施することで得られる。なお、当然のことであるが、前記式(2)のRAが水素原子であるジアミノベンゼン化合物と、前記式(2’’)で示されるジアミノベンゼン化合物とは同じ化合物である。
前記ジアミノベンゼン化合物と前記オルトエステル誘導体との反応は、酸の存在下で行うが、この酸は、特に制限されるものではなく、塩酸、硫酸等の無機酸、蟻酸、酢酸、メタンスルホン酸、p-トルエンスルホン酸などの有機酸を使用することができる、中でも、取り扱いの容易さから、酢酸等の有機酸を使用することが好ましい。この際、使用する酸を反応溶媒とすることもできる。
本発明においては、前記ジアミノベンゼン化合物と前記オルトエステル誘導体とを、酸が存在する雰囲気下で、十分に接触させればよい。
nは1~4の整数であり、好ましくは1であり、
R1は、前記式(1)におけるものと同義であり、
R2は、前記式(3)におけるものと同義である。)で示されるベンズイミダゾール誘導体が得られる。R1の好ましい位置、置換基も前記ニトロベンゼン化合物と同じである。
<HPLCの測定条件>
装置:高速液体クロマトグラフィー(HPLC)
機種:2695-2489-2998(Waters社製)
検出器:紫外吸光光度計(測定波長:210nm)
カラム:Kromasil C18、内径4.6mm、長さ15cm(粒子径5μm)
(AkzoNobel社製)
カラム温度:30℃一定
サンプル温度:25℃一定
移動相A:アセトニトリル
移動相B:15mMリン酸二水素カリウム水溶液(pH=2.5 リン酸にて調整)
移動相の送液:移動相A,Bの混合比を下記表1のように変えて濃度勾配制御する。
測定時間:40分
下記式の反応を行った。
IR(KBr)1693cm-1。
1H-NMR(CDCl3) δ7.30-7.80(m,1H),6.40-7.10(m.2H),1.45(brs,2H),3.85(s,3H),3.40(brs,2H)。
実施例1において、亜ジチオン酸ナトリウム(純度80質量%)(2.22g、10.2mmol((純度から算出したハイドロサルファイトナトリウムのモル数);和光純薬社製、亜ジチオン酸のアルカリ金属塩)を使用し、反応時間を5時間とした以外は、実施例1と同様の操作を行った。転化率は10%であった。極性不純物は確認できなかった。
実施例1において、反応溶媒をDMF(7ml)、水(0.099ml、5.1mmol)の混合溶媒とした以外は、実施例1と同様の操作を行った。2,3-ジアミノ安息香酸メチルの収率は94%であった。転化率は100%であった。また、HPLCで確認した2,3-ジアミノ安息香酸メチルの純度は95.4%であり、極性不純物は2.5%であった。得られた2,3-ジアミノ安息香酸メチルの分析結果は実施例1と同様であった。
実施例1において、反応溶媒としてDMFを7ml使用した以外は、実施例1と同様の操作を行った。2,3-ジアミノ安息香酸メチルの収率は94%であった。転化率は100%であった。また、HPLCで確認した2,3-ジアミノ安息香酸メチルの純度は97.5%であり、極性不純物は確認できなかった。
実施例1において、炭酸カリウム、および反応溶媒の代わりに、15規定 アンモニア水(2.55ml、NH3 38.3mmol)を使用した以外は、実施例1と同様の操作を行った。転化率は21.5%であった。また、極性不純物は確認できなかった。
下記式の反応を行った。還元、および脱保護反応をまとめて示した。
亜ジチオン酸ナトリウム(純度80質量%)(12.5g、57.5mmol)のDMF(25mL)溶液を100℃で30分攪拌した。この溶液に2-tert-ブチルオキシカルボニルアミノ-3-ニトロ安息香酸メチル(5g、16.9mmol、N-保護ニトロベンゼン化合物)、DMF(15mL)、水(1.4mL、77.8mmol)を含む溶液を1時間かけて滴下した。100℃で2時間反応した(攪拌混合した)後、反応液にトルエン(30m)および水(1000ml)を加えた。この混合物に24質量%水酸化ナトリウム水溶液を加えてpHを8.20とした後、酢酸エチルで(30ml)で生成物を抽出した。この抽出を合計4回行った。その後、抽出に使用した酢酸エチル溶液を合計し、水(80ml)で洗浄を3回行った。洗浄後の酢酸エチル溶液を高速液体クロマトグラフィー(HPLC)で確認したところ、転化率は100%であった。また、2-tert-ブチルオキシカルボニル-2,3-ジアミノ安息香酸メチル(N-保護アミノベンゼン化合物)の純度は97.9%であった。極性不純物は確認できなかった。
2-tert-ブチルオキシカルボニル-2,3-ジアミノ安息香酸メチルを含む酢酸エチル溶液に、メタノール(50ml)、濃塩酸(5.1g、51mmol)を加え、50℃で8時間撹拌した。その後、この反応液を、水(200ml)で希釈して、24質量%水酸化ナトリウム水溶液を加えてpHを8.8とした。pHが8.8の混合液を分液して、水層を酢酸エチル(30mL)で4回抽出した。pHが8.8の混合液から分液した最初の有機層と抽出液(酢酸エチル)を合計し、水(80mL)で4回洗浄した。得られた有機層を減圧濃縮することにより、2,3-ジアミノ安息香酸メチル(2.4g、2,3-ジアミノベンゼン化合物、質量から求めた収率:85.7%)を得た。
下記式の反応を行った。
(還元反応;N-保護アミノベンゼン化合物の合成)
直径7.5cmの二枚撹拌翼を備えた500mL四つ口フラスコに2-tert-ブチルオキシカルボニルアミノ-3-ニトロ安息香酸メチル(20g、67.50mmol、N-保護ニトロベンゼン化合物)を量りとり、DMF(60mL)、亜ジチオン酸ナトリウム(純度80質量%)(27.7g、135.01mmol)、水(4.9mL、270.01mmol)を加えて60℃で6時間撹拌しながら反応を行った。反応後の溶液にトルエン(200mL)を加えて抽出した後、1規定水酸化ナトリウム(200ml)で、2回有機層の洗浄を行った。さらに、水(200mL)で1回有機層の洗浄を行った。洗浄後のトルエン溶液を高速液体クロマトグラフィー(HPLC)で確認したところ、2-tert-ブチルオキシカルボニルアミノ-3-ニトロ安息香酸メチル(N-保護ニトロベンゼン化合物)の転化率は100%であった。また、2-tert-ブチルオキシカルボニル-2,3-ジアミノ安息香酸メチルの純度は98.0%であった。極性不純物は確認できなかった。
2-tert-ブチルオキシカルボニル-2,3-ジアミノ安息香酸メチルを含むトルエン溶液に、濃塩酸(15g、150mmol)を加え、50℃で3時間反応を行った。その後、1規定水酸化ナトリウム水溶液(150mL)を加えてpHを約9とした。混合液を分液し、得られた有機層を水(100mL)で2回洗浄した。得られた有機層を減圧濃縮することにより、残渣として2,3-ジアミノ安息香酸メチル(9.9g、2,3-ジアミノベンゼン化合物、質量から求めた収率:88.3%)を得た。
上記、2,3-ジアミノ安息香酸メチルの残渣(9.9g)に酢酸(40mL)、テトラエトキシメタン(12.98g、67.50mmol;オルトエステル誘導体)を加え、20℃で3時間反応を行った。反応後の溶液を冷却した後、14%アンモニア水(120mL)を加えて、中和により2-エトキシ-1H-ベンズイミダゾール-7-カルボン酸メチルを結晶化した。得られたスラリー液を減圧濾過して析出した結晶を分取し、40℃で減圧乾燥して、2-エトキシ-1H-ベンズイミダゾール-7-カルボン酸メチル(11.3g、収率:86%)を得た。また、HPLCで確認した2-エトキシ-1H-ベンズイミダゾール-7-カルボン酸メチルの純度は99.6%であった。
Claims (8)
- 下記式(1)
nは1~4の整数であり、
R1は、炭素数1~6のアルキル基、炭素数1~6のアルコキシ基、炭素数2~6のアシルオキシ基、炭素数2~6のアルコキシカルボニル基、ニトロ基、又はハロゲン原子あり、n≧2の場合には、複数個のR1は互いに同一であっても異なっていてもよく、
RAは、水素原子、又は保護基である。)で示されるアミノニトロベンゼン化合物又はN-保護ニトロベンゼン化合物と、
亜ジチオン酸のアルカリ金属塩とを接触させることにより、
下記式(2)
R1、RAおよびnは、前記式(1)におけるものと同義である。)で示されるジアミノベンゼン化合物又はN-保護アミノベンゼン化合物を製造する方法。 - 非プロトン性極性溶媒を含む反応溶媒中で、前記式(1)で示されるアミノニトロベンゼン化合物又はN-保護ニトロベンゼン化合物と前記亜ジチオン酸のアルカリ金属塩とを接触させることを特徴とする請求項1に記載の方法。
- 前記反応溶媒が水を含み、亜ジチオン酸のアルカリ金属塩を1モルとしたとき、該水の量が1~3モルであることを特徴とする請求項2に記載の方法。
- 炭酸アルカリ金属塩の存在下において、前記式(1)で示されるアミノニトロベンゼン化合物又はN-保護ニトロベンゼン化合物と前記亜ジチオン酸のアルカリ金属塩とを接触させることを特徴とする請求項1~3の何れかに記載の方法。
- 前記式(1)で示されるアミノニトロベンゼン化合物又はN-保護ニトロベンゼン化合物を1モルとしたとき、前記亜ジチオン酸のアルカリ金属塩の使用量が1~5モルであることを特徴とする請求項1~4の何れかに記載の方法。
- 前記式(1)、および(2)において、
RAの保護基が、tert-ブトキシカルボニル基、ベンジルオキシカルボニル基、フルオレニルメトキシカルボニル基、2,2,2-トリクロロエトキシカルボニル基、4-ニトロベンジルオキシカルボニル基、ホルミル基、アセチル基、トシル基、又はノシル基であることを特徴とする請求項1~5の何れかに記載の方法。 - 請求項6に記載の方法により、
下記式(2’)
R1およびnは、前記式(1)におけるものと同義であり、
RA1は、tert-ブトキシカルボニル基、ベンジルオキシカルボニル基、フルオレニルメトキシカルボニル基、2,2,2-トリクロロエトキシカルボニル基、ホルミル基、アセチル基、トシル基、又はノシル基であり
nは1~4の整数である。)で示されるN-保護アミノベンゼン化合物を製造した後、
得られたN-保護アミノベンゼン化合物と、酸、塩基、又は水素とを接触させて、
下記式(2’’)
R1およびnは、前記式(1)におけるものと同義である。)で示されるジアミノベンゼン化合物を製造する方法。
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