- 1,3-Dipolar cycloaddition of diazomethane and diazocyclopropane to 2-fluoro-3-methylbutadiene and thermal transformations of fluorine-containing vinylpyrazolines and vinylcyclopropanes
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Reactions of 2-fluoro-3-methylbuta-1,3-diene with diazomethane in ether at 15°C and with diazocyclopropane generated in situ by decomposition of N-cyclopropyl-N-nitrosourea in the presence of K2CO3 in CH2Cl2 at -10°C selectively involve the double bond at the methyl group to give 3-(1-fluorovinyl)-3-methylpyrazolines. Thermal dediazotization of the latter at 250°C yields 1-(1-fluorovinyl)-1- methylcyclopropane and -spiropentane 5, which are capable of isomerizing, under more severe conditions (400 - 600°C), into 1-fluoro-2-methylcyclopent-1-ene and 5-fluoro-4-methylspiro[2.4]hept-4-ene (7), respectively. Spiropentane derivative 5 partially isomerizes into 1-fluoro-2-methyl-3-methylidenecyclohex- 1-ene. In a similar way, thermolysis of 6-(2,3,3-trifluorocyclobut-1-enyl)-4,5- diazaspiro[2.4]hept-4-ene at 400°C gives a mixture of 1-(spiropentyl)-2,3,3- trifluorocyclobut-1-ene and 2,3,3-trifluoro-1-(2-methylidenecyclobutyl)cyclobut- 1-ene. Thermolysis of 1-cyclopropyl-2,3,3-trifluorocyclobut-1-ene at 550 - 620°C affords a mixture of 1-(trifluorovinyl)cyclopentene and 2,3-difluorotoluene.
- Guseva,Volchkov,Shulishov,Tomilov,Nefedov
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- Two-step regioselective synthesis of 1,2-difluorobenzenes from chlorotrifluoroethylene and buta-l,3-dienes
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The gas-phase copyrolysis of chlorotrifluoroethylene with buta-1,3-diene, penta-1,3-diene, or isoprene in a flow reactor at 440–480°C gave 4-chloro-4,5,5-trifluorocyclohex-1-enes. The latter treated with aqueous KOH under condition of phase-transfer catalysis were selectively converted into 1,2-difluorobenzene, 2,3-difluorotoluene, or 3,4-difluorotoluene.
- Lipkind, M. B.,Nefedov, O. M.,Volchkov, N. V.
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- Method of preparing fluoroaromatic compounds
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The present invention provides a method of preparing ortho-difluorobenzene derivatives, which comprises (a) providing a mixture of cyclohexenes by reacting chlorotrifluoroethylene (CTFE) and 1,3-diene in a flow reactor and distilling the resultant, and (b) dehydrohalogenating the mixture of cyclohexenes with a phase transition catalyst in the presence of alkali metal hydroxide at temperature range of 40 to 150 °C without using any organic solvent. The distillate having low boiling point, which is obtained during distillation of the resultant, is recycled into the flow reactor. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoic acid, which comprises (a) providing a mixture of 4-chloro-1-methyl-4,5,5-trifluorocyclohexene and 5-chloro-1-methyl-4,4,5-trifluorocyclohexene by reacting chlorotrifluoroethylene (CTFE) and isoprene and distilling the resultant, (b) dehydrohalogenating said mixture in the presence of alkali metal hydroxide and a phase transition catalyst to form 3,4-difluorotoluene, (c) reacting said 3,4-difluorotoluene with chlorine gas without using any organic solvent to form 2-chloro-4,5-difluorotoluene, (d) photo-reacting said 2-chloro-4,5-difluorotoluene with chlorine gas under a lighting mercury lamp without using any organic solvent to form 2-chloro-4,5-difluorobenzotrichloride, and (e) reacting said 2-chloro-4,5-difluorobenzotrichloride with aqueous acid solution without using any organic solvent. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoyl chloride by reacting the 2-chloro-4,5-difluorobenzotrichloride of step (e) above with zinc oxide.
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- Method of preparing fluoroaromatic compounds
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The present invention provides a method of preparing ortho-difluorobenzene derivatives, which comprises (a) providing a mixture of cyclohexenes by reacting chlorotrifluoroethylene (CTFE) and 1.3-diene in a flow reactor and distilling the resultant, and (b) dehydrohalogenating the mixture of cyclohexenes with a phase transition catalyst in :he presence of alkali metal hydroxide at temperature range of 40 to 150° C. without using any organic solvent. The distillate having low boiling point, which is obtained during distillation of the resultant, is recycled into the flow reactor. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoic acid, which comprises (a) providing a mixture of 4-chloro-1-methyl-4,5,5-trifluorocyclohexene and 5-chloro-1-methyl-4,4,5-trifluorocyclohexene by reacting chlorotrifluoroethylene (CTFE) and isoprene and distilling the resultant. (b) dehydrohalogenating said mixture in the presence of alkali metal hydroxide and a phase transition catalyst to form 3,4-difluorotoluene, to reacting said 3,4-difluorotoluene with chlorine gas without using any organic solvent to form 2-chloro-4,5-difluorotoluene, (d) photo-reacting said 2-chloro-4,5-difluorotoluene with chlorine gas under a lighting mercury lamp without using any organic solvent to form 2-chloro-4,5-difluorobenzotrichloride, and (e) reacting said 2-chloro-4,5-difluorobenzotrichloride with aqueous acid solution without using any organic solvent. The present invention also provides a method of preparing 2-chloro-4,5-difluorobenzoyl chloride by reacting the 2-chloro-4,5-difluorobenzotrichloride of step (e) above with zinc oxide.
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