CA2090280A1 - Process for the selective dehalogenation of ortho-halogenonitrobenzenes - Google Patents
Process for the selective dehalogenation of ortho-halogenonitrobenzenesInfo
- Publication number
- CA2090280A1 CA2090280A1 CA002090280A CA2090280A CA2090280A1 CA 2090280 A1 CA2090280 A1 CA 2090280A1 CA 002090280 A CA002090280 A CA 002090280A CA 2090280 A CA2090280 A CA 2090280A CA 2090280 A1 CA2090280 A1 CA 2090280A1
- Authority
- CA
- Canada
- Prior art keywords
- acid
- dichloro
- reaction
- nitrobenzene
- copper
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000005695 dehalogenation reaction Methods 0.000 title claims abstract description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910052802 copper Inorganic materials 0.000 claims abstract description 16
- 239000010949 copper Substances 0.000 claims abstract description 16
- 238000006243 chemical reaction Methods 0.000 claims abstract description 15
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 12
- 239000000460 chlorine Substances 0.000 claims abstract description 12
- CIZHSFBFELYEGN-UHFFFAOYSA-N 1,5-dichloro-2-fluoro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC(F)=C(Cl)C=C1Cl CIZHSFBFELYEGN-UHFFFAOYSA-N 0.000 claims abstract description 9
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 claims abstract description 7
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052794 bromium Inorganic materials 0.000 claims abstract description 7
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims abstract description 7
- 150000005181 nitrobenzenes Chemical class 0.000 claims abstract description 7
- JSEVUBOYVADSHX-UHFFFAOYSA-N 1,3-dichloro-2-fluoro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C(F)=C1Cl JSEVUBOYVADSHX-UHFFFAOYSA-N 0.000 claims abstract description 5
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 5
- 239000011737 fluorine Substances 0.000 claims abstract description 5
- 125000005843 halogen group Chemical group 0.000 claims abstract description 5
- 239000001257 hydrogen Substances 0.000 claims abstract description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 5
- 229910052736 halogen Inorganic materials 0.000 claims abstract description 4
- 150000002367 halogens Chemical class 0.000 claims abstract description 4
- 125000001424 substituent group Chemical group 0.000 claims abstract description 3
- 125000004178 (C1-C4) alkyl group Chemical group 0.000 claims abstract 2
- LQNUZADURLCDLV-UHFFFAOYSA-N nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1 LQNUZADURLCDLV-UHFFFAOYSA-N 0.000 claims description 30
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 claims description 14
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 11
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 8
- -1 aliphatic aldehydes Chemical class 0.000 claims description 8
- 239000003638 chemical reducing agent Substances 0.000 claims description 8
- 150000001875 compounds Chemical class 0.000 claims description 8
- 239000005711 Benzoic acid Substances 0.000 claims description 7
- 235000010233 benzoic acid Nutrition 0.000 claims description 7
- 235000019260 propionic acid Nutrition 0.000 claims description 7
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 claims description 6
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical group O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 6
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 6
- NBBJYMSMWIIQGU-UHFFFAOYSA-N Propionic aldehyde Chemical compound CCC=O NBBJYMSMWIIQGU-UHFFFAOYSA-N 0.000 claims description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 6
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 5
- 125000001931 aliphatic group Chemical group 0.000 claims description 5
- VGDZGWPMCGMBEO-UHFFFAOYSA-N 2,4-dichloro-1,5-difluoro-3-nitrobenzene Chemical compound [O-][N+](=O)C1=C(Cl)C(F)=CC(F)=C1Cl VGDZGWPMCGMBEO-UHFFFAOYSA-N 0.000 claims description 4
- 150000001879 copper Chemical class 0.000 claims description 4
- NNBZCPXTIHJBJL-UHFFFAOYSA-N decalin Chemical compound C1CCCC2CCCCC21 NNBZCPXTIHJBJL-UHFFFAOYSA-N 0.000 claims description 4
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 claims description 4
- ZTQSAGDEMFDKMZ-UHFFFAOYSA-N Butyraldehyde Chemical compound CCCC=O ZTQSAGDEMFDKMZ-UHFFFAOYSA-N 0.000 claims description 3
- 235000011054 acetic acid Nutrition 0.000 claims description 3
- 125000003118 aryl group Chemical group 0.000 claims description 3
- 235000019256 formaldehyde Nutrition 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- KDYFGRWQOYBRFD-UHFFFAOYSA-N succinic acid Chemical compound OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 3
- OCJBOOLMMGQPQU-UHFFFAOYSA-N 1,4-dichlorobenzene Chemical compound ClC1=CC=C(Cl)C=C1 OCJBOOLMMGQPQU-UHFFFAOYSA-N 0.000 claims description 2
- CAHQGWAXKLQREW-UHFFFAOYSA-N Benzal chloride Chemical compound ClC(Cl)C1=CC=CC=C1 CAHQGWAXKLQREW-UHFFFAOYSA-N 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 2
- 229940117389 dichlorobenzene Drugs 0.000 claims description 2
- 150000007522 mineralic acids Chemical class 0.000 claims description 2
- 239000003960 organic solvent Substances 0.000 claims description 2
- PXXNTAGJWPJAGM-UHFFFAOYSA-N vertaline Natural products C1C2C=3C=C(OC)C(OC)=CC=3OC(C=C3)=CC=C3CCC(=O)OC1CC1N2CCCC1 PXXNTAGJWPJAGM-UHFFFAOYSA-N 0.000 claims description 2
- 239000008096 xylene Substances 0.000 claims description 2
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims 3
- 150000002762 monocarboxylic acid derivatives Chemical class 0.000 claims 1
- 239000001384 succinic acid Substances 0.000 claims 1
- CSSSAKOGRYYMSA-UHFFFAOYSA-N 1-chloro-2-fluoro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C(F)=C1 CSSSAKOGRYYMSA-UHFFFAOYSA-N 0.000 abstract description 16
- 238000002360 preparation method Methods 0.000 description 7
- 239000000725 suspension Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 5
- 238000004587 chromatography analysis Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 125000001246 bromo group Chemical group Br* 0.000 description 3
- 210000003298 dental enamel Anatomy 0.000 description 3
- 239000012452 mother liquor Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- VMAATSFMXSMKPG-UHFFFAOYSA-N 1,3-dichloro-2-fluoro-5-nitrobenzene Chemical compound [O-][N+](=O)C1=CC(Cl)=C(F)C(Cl)=C1 VMAATSFMXSMKPG-UHFFFAOYSA-N 0.000 description 2
- AUQBBDWDLJSKMI-UHFFFAOYSA-N 1,3-difluoro-5-nitrobenzene Chemical compound [O-][N+](=O)C1=CC(F)=CC(F)=C1 AUQBBDWDLJSKMI-UHFFFAOYSA-N 0.000 description 2
- KMAQZIILEGKYQZ-UHFFFAOYSA-N 1-chloro-3-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC(Cl)=C1 KMAQZIILEGKYQZ-UHFFFAOYSA-N 0.000 description 2
- 229930040373 Paraformaldehyde Natural products 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 150000001299 aldehydes Chemical class 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- FQERLIOIVXPZKH-UHFFFAOYSA-N 1,2,4-trioxane Chemical compound C1COOCO1 FQERLIOIVXPZKH-UHFFFAOYSA-N 0.000 description 1
- RUBQQRMAWLSCCJ-UHFFFAOYSA-N 1,2-difluoro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(F)C(F)=C1 RUBQQRMAWLSCCJ-UHFFFAOYSA-N 0.000 description 1
- WRGKKASJBOREMB-UHFFFAOYSA-N 1,4-dibromo-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC(Br)=CC=C1Br WRGKKASJBOREMB-UHFFFAOYSA-N 0.000 description 1
- RZKKOBGFCAHLCZ-UHFFFAOYSA-N 1,4-dichloro-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC(Cl)=CC=C1Cl RZKKOBGFCAHLCZ-UHFFFAOYSA-N 0.000 description 1
- 150000005208 1,4-dihydroxybenzenes Chemical class 0.000 description 1
- FWIROFMBWVMWLB-UHFFFAOYSA-N 1-bromo-3-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC(Br)=C1 FWIROFMBWVMWLB-UHFFFAOYSA-N 0.000 description 1
- ZCJAYDKWZAWMPR-UHFFFAOYSA-N 1-chloro-2-fluorobenzene Chemical compound FC1=CC=CC=C1Cl ZCJAYDKWZAWMPR-UHFFFAOYSA-N 0.000 description 1
- BFCFYVKQTRLZHA-UHFFFAOYSA-N 1-chloro-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1Cl BFCFYVKQTRLZHA-UHFFFAOYSA-N 0.000 description 1
- WFQDTOYDVUWQMS-UHFFFAOYSA-N 1-fluoro-4-nitrobenzene Chemical class [O-][N+](=O)C1=CC=C(F)C=C1 WFQDTOYDVUWQMS-UHFFFAOYSA-N 0.000 description 1
- DPHCXXYPSYMICK-UHFFFAOYSA-N 2-chloro-1-fluoro-4-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(F)C(Cl)=C1 DPHCXXYPSYMICK-UHFFFAOYSA-N 0.000 description 1
- LETNCFZQCNCACQ-UHFFFAOYSA-N 2-fluoro-4-nitroaniline Chemical compound NC1=CC=C([N+]([O-])=O)C=C1F LETNCFZQCNCACQ-UHFFFAOYSA-N 0.000 description 1
- CZGCEKJOLUNIFY-UHFFFAOYSA-N 4-Chloronitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C=C1 CZGCEKJOLUNIFY-UHFFFAOYSA-N 0.000 description 1
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 description 1
- 238000000297 Sandmeyer reaction Methods 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000006298 dechlorination reaction Methods 0.000 description 1
- 238000006115 defluorination reaction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000006396 nitration reaction Methods 0.000 description 1
- 229920002866 paraformaldehyde Polymers 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 235000000346 sugar Nutrition 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/12—Preparation of nitro compounds by reactions not involving the formation of nitro groups
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
Abstract of the Disclosure:
Process for the selective dehalogenation of ortho-halogenonitrobenzenes The present invention relates to a novel process for the selective dehalogenation of ortho-halogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, wherein, in nitrobenzenes of general formula (I):
(I) wherein X1 and X3 or X1 and X5 are in each case chlorine, bromine or a combination thereof and the remaining substituents X independently of one another are hydrogen, fluorine or C1-C4-alkyl, the halogen atoms X1 and X5 are each replaced with hydrogen atoms by reaction with copper in the presence of a proton donor.
Access to the industrially relevant 4-chloro-3-fluoro-nitrobenzene from 2,4-dichloro-3-fluoronitrobenzene or 2,4-dichloro-5-fluoronitrobenzene is of particular interest.
Process for the selective dehalogenation of ortho-halogenonitrobenzenes The present invention relates to a novel process for the selective dehalogenation of ortho-halogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, wherein, in nitrobenzenes of general formula (I):
(I) wherein X1 and X3 or X1 and X5 are in each case chlorine, bromine or a combination thereof and the remaining substituents X independently of one another are hydrogen, fluorine or C1-C4-alkyl, the halogen atoms X1 and X5 are each replaced with hydrogen atoms by reaction with copper in the presence of a proton donor.
Access to the industrially relevant 4-chloro-3-fluoro-nitrobenzene from 2,4-dichloro-3-fluoronitrobenzene or 2,4-dichloro-5-fluoronitrobenzene is of particular interest.
Description
2~90280 HOECHST AKTIENGESELLSCHAFT HOE 92/F 050 Dr. HU/PL
Description ..
Proces for the selective dehalogenation of ortho-halogenonitrobenzenes The present invention relates to a novel process for the selective dehalogenation of nitrobenzenes containing one or two chlorine or bromine atoms in the 2- and/or 6-position relative to the nitro group.
Industrial access to 4-chloro-3-fluoronitrobenzene is greatly restricted with the synthetic routes conventionally used hitherto. Thus, for example, the nitration of 2-fluorochlorobenzene leads to a mixture of 79% of 3-chloro-4-fluoronitrobenzene and only 21% of 4-chloro 3-fluoronitrobenzene (Houben-Weyl, Methoden der Organischen Chemie (Methods of Organic Chemistry), 4th edition, vol. X/1, p. 507). A Sandmeyer reaction is also unattractive for the preparation of 4-chloro-3- fluoro-nitrobenzene on the industrial scale because of the expensive 6ynthesis of the starting material 2- fluoro-4-nitroaniline.
Japanese patent disclosure Sho-63 156 757 describQs a process for the selective dehalogenation of fluorinated ortho-chloronitrobenzenes with the aid of sodium boro-hydride, although this is too expensive for industrial u~e.
There was therefore considerable interest in a novel, economically sen~ible route to the preparation of halo-genated nitrobenzenes which are selectively dehalogenated in the 2- and 6-position relative to the nitro group, especially for the preparation of 4-chloro-3- fluoro-nitrobenzene, which is a precursor for 3,4-difluoro-nitrobenzene (US-P5 4,036,977; US-PS 4,12n,099; US-PS 4,130,561 and US-PS 4,200,588).
.:
, ..
.
':
209~2~0 It is known that 2-chloronitrobenzene, but not 3-chloro-nitrobenzene or 4-chloronitrobenzene, can be reductively dechlorinated to nitrobenzene with copper in benzoic acid (W.T. Smith Jr., J. Amer. Chem. Soc., 71, 2852 (1949)).
Later, this author also describes the reductive dehalo-genation of 2,5-dichloronitrobenzene and 2,5-dibromo-nitrobenzene to 3-chloronitrobenzene and 3-bromonitro-benzene, respectively, in moderate yields of 37 - 38%
(W.T. Smith Jr. and L. Campanaro, J. Amer. Chem. Soc., 75, 3602 (1953)). He further proves that monofluoronitro-benzenes cannot be reductively defluor.inated with copper/benzoic acid. By contrast, nothing was known about the behavior of nitrobenzenes containing chlorine or bromine atoms in the 2- and 4-position or in the 2- and 6-position relative to the nitro group. Because the electronic conditions in the benzene ring change substantially when additional chlorine or bromine atoms are present or the position of these halogen atoms in the ring alters, it could not be assumed that the method of Smith et al. was suitable for the preparation of 4-chloro-3-fluoronitrobenzene.
It has been found, surprisingly, that both 2,4-di-halogenonitrobenzenes and 2,6-dihalogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, can be selectively dehalogenated in the ortho-position(s) relative to the nitro group u8ing copper with the addition of a proton donor.
Furthermore, it has been found, surprisingly, that the addition of suitable reducing agents makes it possible to cut down the amounts of metallic copper required. The potential of the reducing agents here must be sufficiently high to be able to reduce the copper salts formed in the dehalogenation to metallic copper.
-.
The present invention relates to a process for the selective dehalogenation of ortho-halogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, wherein, in nitrobenzenes of general formula (I):
X 5\ /1, /X
Js 3 ~ (I) X4 \ j / X2 wherein X~ and X3 or Xl and X5 are in each case chlorine, bromine or a combination thereof and the remaining substituents X independently of one another are hydrogen, fluorine or Cl-C4-alkyl, the halogen atoms X~ and X5 are each replaced with hydrogen atoms by reaction with copper, preferably in the presence of a reducing agent capable of reducing copper salts to metallic copper, and in the presence of a proton donor.
Compounds of formula (I) which are of special interest here are those in which Xl and X3 or X~ and X5 are in each case chlorine and x2 and X4 independently of one another are hydrogen or fluorine.
of particular intere~t are the compounds 2,4-dichloro- 3-fluoronitrobenzeneand2,4-dichloro-5-fluoronitrobenzene, which can be converted to 4-chloro-3-fluoronitrobenzene, selectively and in good yields, by the process according to the invention~
Also of interest is the compound 2,6-dichloro-3,5-di-fluoronitrobenzene, which is converted to 3,5-difluoro-:
~0280 nitrobenzene by the process according to the invention.In no case does defluorination take place; likewise, dechlorination does not occur in the para- or meta-position relative to the nitro group.
In the process according to the invention, the addition of suitable reducing agents can cut down the amount of metallic copper required by up to 90~, preferably up to 60~. Suitable reducing agents are any substances whose redox potential is sufficient to reduce the copper salts formed in the dehalogenation to metallic copper. Possible reducing agents in terms of the invention are aldehydes, reducing sugars, polyalcohols and hydroquinones.
Particularly suitable reducing agents, however, are aliphatic aldehydes, especially methanal, ethanal, propanal and butanal, compounds which release methanal or ethanal, such as trioxane, paraformaldehyde and polyoxy-methylene, or a mixture of these compounds.
Proton donors which can be used in the process according to the invention are both inorganic acids, preferably hydrochloric acid, and aromatic monocarboxylic acids, preferably benzoic acid, aromatic dicarboxylic acids, preferably phthalic acid, aromatic polycarboxylic acids and aliphatic monocarboxylic acids, preferably methane-carboxylic acid, ethanecarboxylic acid, propanecarboxylic acid and butanecarboxylic acid, aliphatic dicarboxylic acids, preferably malonic acid and succinic acid, and aliphatic polycarboxylic acids, as well as combinations thereof. The amounts of proton- providing compounds used can be either equal to or greater than or less than the stoichiometric amounts. ~he use of amounts less than the stoichiometric amounts is favorable in all cases where the copper ~alts formed dissolve in the excess acid and hence make the working- up more difficult.
The process according to the invention can be carried out either with or without the addition of a solvent.
2 ~
Convenient organic solvents are all those which are inert towards the reaction according to the invention and which have a high boiling point, preferably benæene, toluene, xylene, dichlorobenzene, dichlorotoluene or decalin, but especially nitrobenzene. The addition of a solvent, especially nitrobenzene, can considerably increase the yield when benzoic acid is used.
The upper limit of the reaction temperature is governed only by the stability of the carboxylic acids used in the presence of copper. Said temperature can be within a very wide range from about 80 to about 300C, preferably 140 to 240C. The reaction according to the invention can be carried out at atmospheric pressure or under excess pressure in an autoclave.
In the Examples which follow, percentages are always by weight. The products were identified with the aid of gas chromatographic analyses.
Examples 1) Preparation of 4-chloro-3-fluoronitrobenzene from 2,4-dichloro-3-fluoronitrobenzene 209.7 g (3.3 mol) of copper powder were suspended in portions at 150C in a ~olution of 630 g (2.7 mol) of 2,4-dichloro-3-fluoronitrobenzene (90%; contains 10% of 3,5-dichloro-4-fluoronitrobenzene) and 402.6 g (3.3 mol) of benzoic acid in 600 g of nitrobenzene, with stirring.
When the addition was complete, stirring was continued for 4 hours, the suspension was filtered with suction, the solid was washed twice with in each case 100 g of nitrobenzene and the combined mother liquors were fractionated to give 355.6 g (83% of theory) of 4-chloro-3-fluoronitrobenzene together with 55 g of ' .
.
.
2~28~
unreacted 3,5-dichloro-4-fluoronitrobenzene and 91 ~ of unreacted 2,4-dichloro-3-fluoronitrobenzene.
2) Preparation of 4-chloro-3-fluoronitrobenzene from 2,4-dichloro-5-fluoronitrobenzene à) 241.5 g (3.8 mol) of copper powder were suspended in portions at 150C in a solution of 630 g (3.0 mol) of 2,4-dichloro-5-fluoronitroben~ene and 463.6 g (3.8 mol) of benzoic acid in 600 g of nitrobenzene, with ~tirring.
When the addition was complete, stirring was continued for 4 hours, the resulting suspension was filtered with suction, the solid was rinsed twice with in each case 200 g of nitrobenzene and the combined mother liquor was washed with 200 g of 10~ sodium hydroxide solution and then with 200 g of water, dried over sodium sulfate and 15 fractionated to give 362.3 g (69% of theory) of 4-chloro-3-fluoronitrobenzene and 104 g of unreacted 2,4-dichloro-5-fluoronitrobenzene.
b) 420 g (2.0 mol) of 2,4-dichloro-5-fluoronitrobenzene were placed at lS0C in a 1 1 round-bottomed flask equipped with a stirrer, a reflux condenser, an internal thermometer and a dropping funnel with stirrer, and a suspension of 158.9 g (2.5 mol) of copper powder in 296 g (4 mol) of propionic acid was added dropwise over one hour. The mixture was then heated for 3 hours at 150C
and the excess propionic acid was distilled off. The resulting suspension was filtered with suction, the residue waY rinsed with nitrobenzene and the mother liquor was fractionatQd to give 247.6 g (71% of theory) of 4-chloro-3-fluoronitrobenzene and 70.1 g of unreacted 2,4-dichloro-S-fluoronitrobenzene.
c) 52.5 g (0.25 mol) of 2,4-dichloro-5-fluoronitrobenzene and 14.5 g (0.25 mol) of propionaldehyde were placed in a glass autoclave equipped with a stirrer and an internal thermometer, 4.5 g (0.07 mol) of copper powder were 35 suspended therein, 9.3 g (0.13 mol) of propionic acid and .
.
2~2~0 6.0 g (0.3 mol) of water were added and the mixture was heated for 6 h at approx. 155C, with stirring. ~11 the constituents volatile up to 80C/ 0.06 bar were then distilled off, the resulting suspension was filtered with suction and the mother liquor was fractionated to give 15.3 g (125% based on copper used) of 4-chloro-3-fluoro-nitrobenzene together with 23.1 g of unreacted 2,4-dichloro-5-fluoronitrobenzene.
d) A suspension of 210.1 g (1.0 mol) of 2,~-dichloro-5-fluoronitrobenzene, 63.6 g (1.0 mol) of copper powder, 74 g (1.0 mol) of propionic acid and 1250 g of nitrobenzene was prepared in a 4 1 enamel autoclave equipped with a stirrer, a nitrogen pressure of approx. 2 bar was established and the mixture was heated for 5 hours at 170C. According to gas chromatographic analysis, the conversion to 3-fluoro-4-chloronitrobenzene after this time was 74.3%.
e) A suspension of 210.1 g (1.0 mol) of 2,4-dichloro-5-fluoronitrobenzene, 63.6 g (1.0 mol) of copper powder, 60.1 g (1.0 mol) of acetic acid and 1250 g of nitro-benzene was prepared in a 4 1 enamel autoclave equipped with a stirrer, a nitrogen pressure of approx. 2 bar was established and the mixture was heated for 12 hours at 170C. According to gas chromatographic analysis, the conversion to 3-fluoro-4-chloronitrobenzene after this time was 50.4~.
f) A su~pen~ion of 210.1 g (1.0 mol) of 2,4-dichloro-5-fluoronitrobenzene, 63.6 g (1.0 mol) of copper powder, 100 g (1.0 mol) of 37~ hydrochloric acid and 1250 g of nitrobenzene was prepared in a 4 1 enamel autoclave equipped with a stirrer, a nitrogen pressure of approx.
2 bar was established and the mixture was heated for 12 hours at 170C. According to gas chromatographic analysis, the conversion to 3-fluoro-4-chloronitrobenzene after this time was 22.5%.
. : . ' - , ' ~ ' :
2~28~
3) Preparation of 3,5-difluoronitrobenzene from 2,6-dichloro-3,5-difluoronitrobenzene A total of 2.5 g (40 mmol~ of copper powder was added in portions at 150C to a solution of 4.6 g (20 mmol) of 2,6-dichloro-3,5-difluoronitrobenzene and 3.0 g (40 mmol) of propionic acid in 20 g of nitrobenzene, with stirring, and stirring was continued for 3 hours at 150C. The conversion to 3,5-difluoronitrobenzene after this time was over 60~ (GC).
Description ..
Proces for the selective dehalogenation of ortho-halogenonitrobenzenes The present invention relates to a novel process for the selective dehalogenation of nitrobenzenes containing one or two chlorine or bromine atoms in the 2- and/or 6-position relative to the nitro group.
Industrial access to 4-chloro-3-fluoronitrobenzene is greatly restricted with the synthetic routes conventionally used hitherto. Thus, for example, the nitration of 2-fluorochlorobenzene leads to a mixture of 79% of 3-chloro-4-fluoronitrobenzene and only 21% of 4-chloro 3-fluoronitrobenzene (Houben-Weyl, Methoden der Organischen Chemie (Methods of Organic Chemistry), 4th edition, vol. X/1, p. 507). A Sandmeyer reaction is also unattractive for the preparation of 4-chloro-3- fluoro-nitrobenzene on the industrial scale because of the expensive 6ynthesis of the starting material 2- fluoro-4-nitroaniline.
Japanese patent disclosure Sho-63 156 757 describQs a process for the selective dehalogenation of fluorinated ortho-chloronitrobenzenes with the aid of sodium boro-hydride, although this is too expensive for industrial u~e.
There was therefore considerable interest in a novel, economically sen~ible route to the preparation of halo-genated nitrobenzenes which are selectively dehalogenated in the 2- and 6-position relative to the nitro group, especially for the preparation of 4-chloro-3- fluoro-nitrobenzene, which is a precursor for 3,4-difluoro-nitrobenzene (US-P5 4,036,977; US-PS 4,12n,099; US-PS 4,130,561 and US-PS 4,200,588).
.:
, ..
.
':
209~2~0 It is known that 2-chloronitrobenzene, but not 3-chloro-nitrobenzene or 4-chloronitrobenzene, can be reductively dechlorinated to nitrobenzene with copper in benzoic acid (W.T. Smith Jr., J. Amer. Chem. Soc., 71, 2852 (1949)).
Later, this author also describes the reductive dehalo-genation of 2,5-dichloronitrobenzene and 2,5-dibromo-nitrobenzene to 3-chloronitrobenzene and 3-bromonitro-benzene, respectively, in moderate yields of 37 - 38%
(W.T. Smith Jr. and L. Campanaro, J. Amer. Chem. Soc., 75, 3602 (1953)). He further proves that monofluoronitro-benzenes cannot be reductively defluor.inated with copper/benzoic acid. By contrast, nothing was known about the behavior of nitrobenzenes containing chlorine or bromine atoms in the 2- and 4-position or in the 2- and 6-position relative to the nitro group. Because the electronic conditions in the benzene ring change substantially when additional chlorine or bromine atoms are present or the position of these halogen atoms in the ring alters, it could not be assumed that the method of Smith et al. was suitable for the preparation of 4-chloro-3-fluoronitrobenzene.
It has been found, surprisingly, that both 2,4-di-halogenonitrobenzenes and 2,6-dihalogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, can be selectively dehalogenated in the ortho-position(s) relative to the nitro group u8ing copper with the addition of a proton donor.
Furthermore, it has been found, surprisingly, that the addition of suitable reducing agents makes it possible to cut down the amounts of metallic copper required. The potential of the reducing agents here must be sufficiently high to be able to reduce the copper salts formed in the dehalogenation to metallic copper.
-.
The present invention relates to a process for the selective dehalogenation of ortho-halogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, wherein, in nitrobenzenes of general formula (I):
X 5\ /1, /X
Js 3 ~ (I) X4 \ j / X2 wherein X~ and X3 or Xl and X5 are in each case chlorine, bromine or a combination thereof and the remaining substituents X independently of one another are hydrogen, fluorine or Cl-C4-alkyl, the halogen atoms X~ and X5 are each replaced with hydrogen atoms by reaction with copper, preferably in the presence of a reducing agent capable of reducing copper salts to metallic copper, and in the presence of a proton donor.
Compounds of formula (I) which are of special interest here are those in which Xl and X3 or X~ and X5 are in each case chlorine and x2 and X4 independently of one another are hydrogen or fluorine.
of particular intere~t are the compounds 2,4-dichloro- 3-fluoronitrobenzeneand2,4-dichloro-5-fluoronitrobenzene, which can be converted to 4-chloro-3-fluoronitrobenzene, selectively and in good yields, by the process according to the invention~
Also of interest is the compound 2,6-dichloro-3,5-di-fluoronitrobenzene, which is converted to 3,5-difluoro-:
~0280 nitrobenzene by the process according to the invention.In no case does defluorination take place; likewise, dechlorination does not occur in the para- or meta-position relative to the nitro group.
In the process according to the invention, the addition of suitable reducing agents can cut down the amount of metallic copper required by up to 90~, preferably up to 60~. Suitable reducing agents are any substances whose redox potential is sufficient to reduce the copper salts formed in the dehalogenation to metallic copper. Possible reducing agents in terms of the invention are aldehydes, reducing sugars, polyalcohols and hydroquinones.
Particularly suitable reducing agents, however, are aliphatic aldehydes, especially methanal, ethanal, propanal and butanal, compounds which release methanal or ethanal, such as trioxane, paraformaldehyde and polyoxy-methylene, or a mixture of these compounds.
Proton donors which can be used in the process according to the invention are both inorganic acids, preferably hydrochloric acid, and aromatic monocarboxylic acids, preferably benzoic acid, aromatic dicarboxylic acids, preferably phthalic acid, aromatic polycarboxylic acids and aliphatic monocarboxylic acids, preferably methane-carboxylic acid, ethanecarboxylic acid, propanecarboxylic acid and butanecarboxylic acid, aliphatic dicarboxylic acids, preferably malonic acid and succinic acid, and aliphatic polycarboxylic acids, as well as combinations thereof. The amounts of proton- providing compounds used can be either equal to or greater than or less than the stoichiometric amounts. ~he use of amounts less than the stoichiometric amounts is favorable in all cases where the copper ~alts formed dissolve in the excess acid and hence make the working- up more difficult.
The process according to the invention can be carried out either with or without the addition of a solvent.
2 ~
Convenient organic solvents are all those which are inert towards the reaction according to the invention and which have a high boiling point, preferably benæene, toluene, xylene, dichlorobenzene, dichlorotoluene or decalin, but especially nitrobenzene. The addition of a solvent, especially nitrobenzene, can considerably increase the yield when benzoic acid is used.
The upper limit of the reaction temperature is governed only by the stability of the carboxylic acids used in the presence of copper. Said temperature can be within a very wide range from about 80 to about 300C, preferably 140 to 240C. The reaction according to the invention can be carried out at atmospheric pressure or under excess pressure in an autoclave.
In the Examples which follow, percentages are always by weight. The products were identified with the aid of gas chromatographic analyses.
Examples 1) Preparation of 4-chloro-3-fluoronitrobenzene from 2,4-dichloro-3-fluoronitrobenzene 209.7 g (3.3 mol) of copper powder were suspended in portions at 150C in a ~olution of 630 g (2.7 mol) of 2,4-dichloro-3-fluoronitrobenzene (90%; contains 10% of 3,5-dichloro-4-fluoronitrobenzene) and 402.6 g (3.3 mol) of benzoic acid in 600 g of nitrobenzene, with stirring.
When the addition was complete, stirring was continued for 4 hours, the suspension was filtered with suction, the solid was washed twice with in each case 100 g of nitrobenzene and the combined mother liquors were fractionated to give 355.6 g (83% of theory) of 4-chloro-3-fluoronitrobenzene together with 55 g of ' .
.
.
2~28~
unreacted 3,5-dichloro-4-fluoronitrobenzene and 91 ~ of unreacted 2,4-dichloro-3-fluoronitrobenzene.
2) Preparation of 4-chloro-3-fluoronitrobenzene from 2,4-dichloro-5-fluoronitrobenzene à) 241.5 g (3.8 mol) of copper powder were suspended in portions at 150C in a solution of 630 g (3.0 mol) of 2,4-dichloro-5-fluoronitroben~ene and 463.6 g (3.8 mol) of benzoic acid in 600 g of nitrobenzene, with ~tirring.
When the addition was complete, stirring was continued for 4 hours, the resulting suspension was filtered with suction, the solid was rinsed twice with in each case 200 g of nitrobenzene and the combined mother liquor was washed with 200 g of 10~ sodium hydroxide solution and then with 200 g of water, dried over sodium sulfate and 15 fractionated to give 362.3 g (69% of theory) of 4-chloro-3-fluoronitrobenzene and 104 g of unreacted 2,4-dichloro-5-fluoronitrobenzene.
b) 420 g (2.0 mol) of 2,4-dichloro-5-fluoronitrobenzene were placed at lS0C in a 1 1 round-bottomed flask equipped with a stirrer, a reflux condenser, an internal thermometer and a dropping funnel with stirrer, and a suspension of 158.9 g (2.5 mol) of copper powder in 296 g (4 mol) of propionic acid was added dropwise over one hour. The mixture was then heated for 3 hours at 150C
and the excess propionic acid was distilled off. The resulting suspension was filtered with suction, the residue waY rinsed with nitrobenzene and the mother liquor was fractionatQd to give 247.6 g (71% of theory) of 4-chloro-3-fluoronitrobenzene and 70.1 g of unreacted 2,4-dichloro-S-fluoronitrobenzene.
c) 52.5 g (0.25 mol) of 2,4-dichloro-5-fluoronitrobenzene and 14.5 g (0.25 mol) of propionaldehyde were placed in a glass autoclave equipped with a stirrer and an internal thermometer, 4.5 g (0.07 mol) of copper powder were 35 suspended therein, 9.3 g (0.13 mol) of propionic acid and .
.
2~2~0 6.0 g (0.3 mol) of water were added and the mixture was heated for 6 h at approx. 155C, with stirring. ~11 the constituents volatile up to 80C/ 0.06 bar were then distilled off, the resulting suspension was filtered with suction and the mother liquor was fractionated to give 15.3 g (125% based on copper used) of 4-chloro-3-fluoro-nitrobenzene together with 23.1 g of unreacted 2,4-dichloro-5-fluoronitrobenzene.
d) A suspension of 210.1 g (1.0 mol) of 2,~-dichloro-5-fluoronitrobenzene, 63.6 g (1.0 mol) of copper powder, 74 g (1.0 mol) of propionic acid and 1250 g of nitrobenzene was prepared in a 4 1 enamel autoclave equipped with a stirrer, a nitrogen pressure of approx. 2 bar was established and the mixture was heated for 5 hours at 170C. According to gas chromatographic analysis, the conversion to 3-fluoro-4-chloronitrobenzene after this time was 74.3%.
e) A suspension of 210.1 g (1.0 mol) of 2,4-dichloro-5-fluoronitrobenzene, 63.6 g (1.0 mol) of copper powder, 60.1 g (1.0 mol) of acetic acid and 1250 g of nitro-benzene was prepared in a 4 1 enamel autoclave equipped with a stirrer, a nitrogen pressure of approx. 2 bar was established and the mixture was heated for 12 hours at 170C. According to gas chromatographic analysis, the conversion to 3-fluoro-4-chloronitrobenzene after this time was 50.4~.
f) A su~pen~ion of 210.1 g (1.0 mol) of 2,4-dichloro-5-fluoronitrobenzene, 63.6 g (1.0 mol) of copper powder, 100 g (1.0 mol) of 37~ hydrochloric acid and 1250 g of nitrobenzene was prepared in a 4 1 enamel autoclave equipped with a stirrer, a nitrogen pressure of approx.
2 bar was established and the mixture was heated for 12 hours at 170C. According to gas chromatographic analysis, the conversion to 3-fluoro-4-chloronitrobenzene after this time was 22.5%.
. : . ' - , ' ~ ' :
2~28~
3) Preparation of 3,5-difluoronitrobenzene from 2,6-dichloro-3,5-difluoronitrobenzene A total of 2.5 g (40 mmol~ of copper powder was added in portions at 150C to a solution of 4.6 g (20 mmol) of 2,6-dichloro-3,5-difluoronitrobenzene and 3.0 g (40 mmol) of propionic acid in 20 g of nitrobenzene, with stirring, and stirring was continued for 3 hours at 150C. The conversion to 3,5-difluoronitrobenzene after this time was over 60~ (GC).
Claims (11)
1. A process for the selective dehalogenation of ortho-halogenonitrobenzenes, halogen being chlorine, bromine or a combination thereof, wherein, in nitro-benzenes of general formula (I):
(I) wherein X1 and X3 or X1 and X5 are in each case chlorine, bromine or a combination thereof and the remaining substituents X independently of one another are hydrogen, fluorine or C1-C4-alkyl, the halogen atoms X1 and X5 are each replaced with hydrogen atoms by reaction with copper in the presence of a proton donor.
(I) wherein X1 and X3 or X1 and X5 are in each case chlorine, bromine or a combination thereof and the remaining substituents X independently of one another are hydrogen, fluorine or C1-C4-alkyl, the halogen atoms X1 and X5 are each replaced with hydrogen atoms by reaction with copper in the presence of a proton donor.
2. The process as claimed in claim 1, wherein, in the compound of formula (I), X1 and X3 or X1 and X5 are in each case chlorine and X2 and X4 independently of one another are hydrogen or fluorine.
3. The process as claimed in claim 1 or 2, wherein the compound of formula (I) is 2,4-dichloro-3-fluoro-nitrobenzene, 2,4-dichloro-5-fluoronitrobenzene or 2,6- dichloro-3,5-difluoronitrobenzene.
4. The process as claimed in at least one of claims 1 to 3, wherein, in nitrobenzenes of general formula (I), the halogen atoms X1 and X5 are each replaced with hydrogen atoms by reaction with copper and a reducing agent whose potential is sufficient to reduce copper salts to metallic copper, preferably aliphatic aldehydes, in the presence of a proton donor.
5. The process as claimed in claim 4, wherein the aliphatic aldehyde is methanal, ethanal, propanal, butanal or a mixture thereof.
6. The process as claimed in at least one of claims 1 to 5, wherein the proton donor used is an inorganic acid, an aromatic monocarboxylic acid, an aromatic dicarboxylic acid, an aromatic polycarboxylic acid, an aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid, an aliphatic polycarboxylic acid or a mixture thereof.
7. The process as claimed in at least one of claims 1 to 6, wherein the proton donor used is hydrochloric acid, benzoic acid, phthalic acid, acetic acid, propionic acid, malonic acid, succinic acid or a mixture thereof.
8. The process as claimed in at least one of claims 1 to 7, wherein the reaction is carried out without the addition of a solvent.
9. The process as claimed in at least one of claims 1 to 7, wherein the reaction is carried out in the presence of an organic solvent which is inert towards the reaction in question, preferably benzene, toluene, xylene, dichlorobenzene, dichloro-toluene, decalin, nitrobenzene or a mixture thereof.
10. The process as claimed in at least one of claims 1 to 7, wherein the reaction is carried out in the presence of nitrobenzene.
11. The process as claimed in at least one of claims 1 to 10, wherein the proton donor is used in amounts less than the stoichiometric amounts, based on the ortho-halogenonitrobenzene used.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4205680 | 1992-02-25 | ||
| DEP4205680.2 | 1992-02-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2090280A1 true CA2090280A1 (en) | 1993-08-26 |
Family
ID=6452490
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002090280A Abandoned CA2090280A1 (en) | 1992-02-25 | 1993-02-24 | Process for the selective dehalogenation of ortho-halogenonitrobenzenes |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0557878A1 (en) |
| JP (1) | JPH069509A (en) |
| CA (1) | CA2090280A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5886210A (en) * | 1996-08-22 | 1999-03-23 | Rohm And Haas Company | Method for preparing aromatic compounds |
| CN101842173B (en) * | 2007-11-02 | 2012-12-26 | 新日本制铁株式会社 | Strip rolling mill and its control method |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2259810A1 (en) * | 1974-02-06 | 1975-08-29 | Rhone Poulenc Ind | Meta and/or para halogen substd. nitrobenzenes prepn. - by reacting the tri- to pentahelogenated cpds. with copper and org. acid |
| JPS6179482U (en) * | 1984-10-31 | 1986-05-27 | ||
| JPS61123487U (en) * | 1985-01-21 | 1986-08-04 | ||
| JPS62145282U (en) * | 1986-03-07 | 1987-09-12 | ||
| JPH0422080A (en) * | 1990-05-17 | 1992-01-27 | Fujitsu Ltd | Housing structure for rectangular connector |
-
1993
- 1993-02-17 EP EP93102452A patent/EP0557878A1/en not_active Withdrawn
- 1993-02-23 JP JP5033635A patent/JPH069509A/en not_active Withdrawn
- 1993-02-24 CA CA002090280A patent/CA2090280A1/en not_active Abandoned
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| Publication number | Publication date |
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| JPH069509A (en) | 1994-01-18 |
| EP0557878A1 (en) | 1993-09-01 |
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