Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1998-05-14
1999-07-20
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
564 80, 564 83, 568 33, 568 35, C07C30300
Patent
active
059257881
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a new process for the preparation of 2-trifluoromethoxy-benzenesulphonamide, which is known as starting material for herbicidally active compounds.
It is known that 2-trifluoromethoxy-benzenesulphonamide is obtained when 2-trifluoromethoxy-benzene sulphochloride is reacted with ammonia (cf. Zh. Org. Khim. 8 (1972), 1023-1026 (russ.) a.k.a. J. Org. Chem. USSR 8 (1972), 1032-1035 (engl.)--cited in Chem. Abstracts 77:61964; cf. also U.S. Pat. No. 4,732,711).
While this reaction proceeds smoothly and yields 2-trifluoromethoxy-benzenesulphonamide in high yields and in good quality, the trifluoromethoxy-benzene sulphochloride required as starting material must be prepared beforehand from 2-trifluoromethoxy-aniline via a so-called Meerwein reaction, which, when carried out technically, is relatively complicated. Moreover, 2-trifluoromethoxy-aniline, which is required as a precursor, is available in limited quantities only.
It has now been found that 2-trifluoromethoxy-benzenesulphonamide, of the formula ##STR3## is obtained in very good yields and in high purity when halogenated trifluoromethoxy-benzenesulphonamides of the general formula (II) ##STR4## in which
X.sup.1 represents halogen and
X.sup.2 represents hydrogen or halogen of a diluent and, if appropriate, in the presence of an acid acceptor at temperatures between 0.degree. C. and 200.degree. C. ("dehalogenated"), the resulting compound of the formula (I) is isolated in the customary manner in the event that "X.sup.2 =halogen" and converted into a pure, crystalline product by treating it with a protic polar organic liquid and isolated by removing the liquid component by means of filtration with suction in the event that "X.sup.2 =H".
The general formula (II) represents the formulae (IIA) and (IIB) ##STR5## where in formula (IIA)
X.sup.1 and X.sup.2 have the abovementioned meanings and
X.sup.1 has the abovementioned meaning and X.sup.2 represents only hydrogen.
Surprisingly, the trifluoromethoxy group is not changed during hydrogenolytic dehalogenation. Another highly surprising feature is that, in the event that "X.sup.2 =H", the undesired, isomeric reaction product--3-trifluoromethoxy-benzenesulphonamide--can be dissolved by simple treatment with a protic polar organic liquid and thus removed readily, while the desired product of the formula (I) remains virtually undissolved and can thus be isolated readily by filtration with suction.
The process according to the invention is thus a valuable enrichment of the prior art.
Formula (II) provides a general definition of the halogenated trifluoromethoxy-benzenesulphonamides to be used as starting materials in the process according to the invention for the preparation of 2-trifluoromethoxy-benzenesulphonamide.
In formula (II),
X.sup.1 preferably represents chlorine or bromine, and
X.sup.2 preferably represents hydrogen or chlorine.
In the event that "X.sup.2 =H", the starting materials are employed in the form of a mixture of the compounds of the formulae (IIA) and (IIB), the compound of the formula (IIA) preferably amounting to over 60%. In the event that "X.sup.2 =halogen", the starting materials are those of the formula (IIA).
The starting materials of the formula (II, where X.sup.2 =H) are known and/or can be prepared by processes known per se (cf. EP-A 23 422, EP-A 64,322). The starting materials of the formula (II, where X.sup.2 =halogen) are new and also a subject-matter of the invention (cf. Preparation Examples).
The process according to the invention is carried out in the presence of a diluent. Suitable diluents are, preferably, water and organic solvents, in particular alcohols such as methanol, ethanol, n- or i-propanol, n-, i-, s- or t-butanol, ethers such as methyl t-butyl ether, methyl t-pentyl ether, ethylene gylcol dimethyl ether or tetrahydrofuran, ether alcohols such as ethylene glycol monomethyl ether or ethylene glycol monoethyl ether, furthermore hydrocarbons such as hexane, cyclohexane, methylcyclohexane, toluene or xylenes, or else mixtures of the abovementioned
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Belinskaya et al., "Pyrolysis of Lithium . . . Benzenesulfonate," Institute of Organic Chemistry, Academy of Sciences of the Ukrainian SSR. Translated from Zhurnal Organicheskoi Khimii, vol.8, No.5, pp. 1023-1026 (1972).
Kysela Ernst
Lantzsch Reinhard
Marhold Albrecht
Bayer Aktiengesellschaft
Geist Gary
Vollano Jean F.
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