Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1987-07-15
1989-08-22
Ford, John M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D28516
Patent
active
048597724
DESCRIPTION:
BRIEF SUMMARY
The present invention is related to the preparation of the known contact herbicidally active 3-isopropyl-benzo-2-thia-1,3-diazinone-(4)-2,2-dioxide (bentazone). The preparation and use of bentazone is disclosed in DAS Nos. 1 542 836 and 2 105 687.
According to the state of art and industrial experiences the bentazone can be best prepared by using as the starting material an anthranylic acid alkyl ester by reacting the same with isopropyl sulfamoyl chloride and after condensation and cyclization the end product may be isolated. Condensation and cyclization may be carried out in one step, i.e. the condensed product need not be isolated. This process is disclosed in detail in German Patent Specification No. 2 357 063, according to which anthranylic acid methyl ester is reacted with isopropyl sulfamoyl chloride in toluene at 60.degree. C. in the presence of tri-n-butyl amine as an acid binding agent. The thus obtained product is then subjected to cyclization without isolating the intermediate product in the presence of NaOCH.sub.3 within 1 hour at 60.degree.-80.degree. C. Yield: 93%, melting point of the obtained bentazone: 130.degree.-132.degree. C.
The drawback of the known process is the necessity of the intermediate isopropyl sulfamoyl chloride for the synthesis. The preparation of this intermediate product is accompanied by severe difficulties on an industrial scale. This is why an adduct of picoline and SO.sub.3 is used instead of sulfamoyl chloride according to German Patent Specification No. 2 710 382 and European Patent Specification No. 70 147, by reacting anthranylic acid isopropyl amide with an adduct of SO.sub.3 and picoline, resulting in 1-(isopropyl-amido-carbonyl)-phenylsulfamic acid and by converting same to bentazone in the presence of POCl.sub.3 while eliminating water.
The preparation of isopropyl-sulfamoyl chloride is discussed by G. Hamprecht et al. in Angewandte Chemie (93, 151-163, 1981).
In German Patent Specification No. 2 164 197 a process is suggested for the preparation of N-alkyl-sulfamidic acid starting from the corresponding alkyl isocyanate by reacting the same with sulfuric acid. The obtained sulfamidic acid is chlorinated with PCl.sub.5 in chloroform according to German Patent Specification No. 2 164 176 and the end product being isopropyl sulfamoyl chloride is distilled in vacuo. The yield of the chlorination amounts to 85.5, the yield of the preparation of Nalkyl-sulfamidic acid is not given.
According to German Patent Specification No. 2 424 371 isopropyl sulfamidic acid is prepared by reacting N,N'-diisopropyl-urea in an organic solvent with sulfur trioxide in the first step and with sulfuric acid in the second step. A disadvantage of this process is the necessity of a significant molar excess of sulfur trioxide and its disposal is also problematic, further the preparation of SO.sub.3 from oleum by distillation or with inert gas demands an expensive apparatus.
According to German Patent Specification No. 2 852 274 alkyl sulfamoyl chloride is prepared by converting alkyl isocyanate or dialkyl urea with oleum or sulfuric acid to alkyl sulfamidic acid then with chlorinating agents in one step to alkyl sulfamoyl chloride. The preparation of isopropyl sulfamoyl chloride is not disclosed, only the chlorination step is described which can be performed with a yield of 76%. The quality of the end product is not disclosed.
Summarizing the methods for the preparation of bentazone one can see that only some steps of the several step - synthesis methods are dealt with and that the quality of the end product is not appropriate.
In German Patent Specifications Nos. 2 105 687 and 2 357 063 the condensation of isopropyl sulfamoyl chloride and anthranylic acid or ester and the subsequent cyclization are disclosed. The end product melts at 124.degree.-132.degree. C.
Bentazone prepared according to German Patent Specification No. 1 542 836 has to be purified. The purification of the crude bentazone is described in German Patent Specification No. 2 316 292 by dissolving the product in a first
REFERENCES:
patent: 3822257 (1974-07-01), Hamprecht et al.
patent: 3935201 (1976-01-01), Mangold et al.
patent: 4139700 (1979-02-01), Kloek
patent: 4208514 (1980-06-01), McKendry et al.
Dioszegi Erzsebet
Fodor, deceased Ferenc
Horvath Andras
Karacsonyi Bela
Kolonics Zoltan
Ford John M.
Nitro Kemia Ipartelepek
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