Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D241/00—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings
  • C07D241/36—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings condensed with carbocyclic rings or ring systems
  • C07D241/50—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings condensed with carbocyclic rings or ring systems with hetero atoms directly attached to ring nitrogen atoms
  • C07D241/52—Oxygen atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D241/00—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings
  • C07D241/36—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings condensed with carbocyclic rings or ring systems
  • C07D241/38—Heterocyclic compounds containing 1,4-diazine or hydrogenated 1,4-diazine rings condensed with carbocyclic rings or ring systems with only hydrogen or carbon atoms directly attached to the ring nitrogen atoms
  • C07D241/40—Benzopyrazines
  • C07D241/44—Benzopyrazines 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 to carbon atoms of the hetero ring

Definitions

• the invention relates to an improved process compared to the prior art for the preparation of 2,6-dichloroquinoxaline by reducing 6-chloro-2-hydroxyquinoxaline-N-oxide to 6-chloro-2-hydroxyquinoxaline, crystallizing its sodium salt, removing the Water and chlorination in a manner known per se.
• 2,6-dichloroquinoxaline is an important intermediate for the production of crop protection agents (EP 276 741A; DE-OS 30 04 770). It is important that the 2,6-dichloroquinoxaline is used in pure form. All known processes for the preparation of 2,6-dichloroquinoxaline (cf. EP 0 295 815; EP 0 295 797; USP 4,636,562; Sakata et al., Heterocycles £ 3, 143, 2025 (1985); DE 3 901 406; European patent application 89 106 784.5, in conjunction with Houben-Weyl, Vol. VIII, 359 ff.
• 2,6-dichloroquinoxaline can be prepared in high purity and at the same time in very good yield by using 6-chloro-2-hydroxyquinoxaline N-oxide in aqueous sodium hydroxide solution in the presence of about 0.001 to about 0.5 mol percent, preferably 0.01 to about 0.05 mol percent of a platinum coated catalyst, based on the 6-chloro-2-hydroxyquinoxaline-N-oxide used, at temperatures of about 20 to about 120 ° C., preferably of about 60 up to about 100 ⁇ C, at a hydrogen pressure of about 1 to about 100 bar, preferably from about 5 to about 20 bar, with about 1 to about 3 equivalents of sodium hydroxide, based on 6-chloro-2-hydroxyquinoxaline-N-oxide, are present, hydrogenated, after separating the catalyst from the hot solution, the 6-chloro-2-hydroxyquinoxaline dissolved therein by cooling the reaction solution to a temperature of about 0 to about 20 ° C., preferably
• the 6-chloro-2-hydroxyquinoxaline-N-oxide in the aqueous sodium hydroxide solution in a concentration of about 15 to about 30 percent by weight, preferably from about 20 to about 25 percent by weight, in the form of the hydrogenation subject.
• the catalytic hydrogenation increases as a function of reaction parameters, for about 30 minutes to about 5 hours, usually about '* l to about 3 hours.
• Shell catalysts are hydrogenation catalysts in which the noble metal, for example platinum, is in its finest form and is predominantly distributed on the surface of a carrier material particle, for example activated carbon, in contrast to what is usually to be designated Precious metal catalysts that have a predominantly uniform distribution of the noble metal also within (via pores, etc.) of a carrier material particle.
• the noble metal for example platinum
• a carrier material particle for example activated carbon
• the catalyst used can be used repeatedly.
• the sodium salt of 6-chloro-2-hydroxyquinoxaline formed by the hydrogenation is in solution under the reaction conditions and can be easily separated from the catalyst. Upon subsequent cooling to about 0 to about 20 ° C, preferably about 5 to about 10 ° C, it is practically quantitative. The product thus obtained is of excellent quality.
• an inert diluent which can form an azeotrope with water.
• suitable diluents are benzene, toluene, xylenes (all isomers and their mixtures), cumene, chlorobenzene, ethylbenzene, carbon tetrachloride, trichloromethane, cyclohexane, hexane, heptane and suitable petroleum ether fractions. Then the water contained is separated off azeotropically.
• the 6-chloro-2-hydroxyquinoxaline obtained at the end of the hydrogenation stage in high purity and in very good yield as such, it can be added to the separated sodium salt by adding a mineral acid such as sulfuric or hydrochloric acid 6-chloro-2 * -hydroxyquinoxaline or preferably to an * aqueous solution of this compound in simple catfish be kept pure.
• a mineral acid such as sulfuric or hydrochloric acid 6-chloro-2 * -hydroxyquinoxaline or preferably to an * aqueous solution of this compound in simple catfish be kept pure.
• a dried sample of the sodium salt showed the following

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Plural Heterocyclic Compounds (AREA)

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Citations (3)

• 1989
  • 1989-08-05 DE DE19893925969 patent/DE3925969A1/de not_active Withdrawn
• 1990
  • 1990-07-16 JP JP2510679A patent/JPH04507406A/ja active Pending
  • 1990-07-16 CA CA 2064564 patent/CA2064564A1/en not_active Abandoned
  • 1990-07-16 WO PCT/EP1990/001162 patent/WO1991001977A1/de not_active Ceased
  • 1990-07-18 IN IN601/CAL/90A patent/IN169080B/en unknown

Patent Citations (3)

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