Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C315/00—Preparation of sulfones; Preparation of sulfoxides
  • C07C315/02—Preparation of sulfones; Preparation of sulfoxides by formation of sulfone or sulfoxide groups by oxidation of sulfides, or by formation of sulfone groups by oxidation of sulfoxides

Definitions

• the above-described herbicidal compounds can have the following structural formula
• R is hydrogen, halogen, nitro, C.-C- alkyl, C -C alkoxy or trifluoromethyl; R 7 through R12 are hydrogen or
• R is hydrogen, halogen, C.-C alkoxy, C 1 -C 4 alkyi, -OCH 2 CH 2 OCH 3 ,-OCH 2 CH 2 OC 2 H 5 , or a substituted alkyl preferably C.-C. alkoxy, C -C alkyl, C,-C. haloalkyl, -CH 2 CH 2 OCH 3 ,-CH 2 CH 2 OC 2 H 5 , or C 1 ⁇ C 2 alkoxy methylene; and R 3 is C.-C. alkyl or C.-C. haloalkyl.
• herbicides can be prepared by reacting a dione of the structural formula
• R through R are as defined with a mole of a trisubstituted benzoyl chloride compound of the structural formula
• R 1, R2 and R3 are as defined above.
• the process of the present invention relates to the preparation of precursor trisubstituted benzoic acid intermediates that are easily converted to the above, de ⁇ scribed trisubstituted benzoyl chloride compounds.
• U.S. 4,780,127 teaches the preparation of 2,3 disubstituted-4-(alkylsulfonyl) benzoic acid by the oxidation of the corresponding 2,3-disubstituted-4-(alkylthio) benzoic acid with an oxidizing agent such as sodium hypochlorite or m-chloroperbenzoic acid in a solvent such as methylene chloride. Hydrogen peroxide is not specifically recited as an oxidizing agent.
• hydrogen peroxide (H_0 2 ) is a well known oxidizing agent for converting aliphatic or aromatic sulfides to sulfoxides.
• the hydrogen peroxide is used with an equal mole amount of formic acid which reacts with the hydrogen peroxide to form the more active performic acid oxidizing agent.
• the oxidation reaction yields formic acid which is an undesireable reaction product for the process of this invention.
• Hydrogen peroxide for safety reasons, normally is diluted with water to concentrations of about 30 or 50 percent by weight when used as an oxidizing agent. When these 30 or 50 percent hydrogen peroxide solutions are used as an oxidizing agent for sulfides the reaction is very slow at normal temperatures (20°C - 100°C).
• R' - S - R" + H 2 0 2 > R' - S(O) - R , H 2 0
• the concentration of the aqueous hydrogen peroxide solution is increasingly diluted with additional water that is created by the reaction and increasingly the hydrogen peroxide becomes less effective as an oxidizing agents as the concentration of the aqueous solution of hydrogen peroxide becomes less and less.
• the present invention relates to an improved process for the preparation of the hereinafter-described sulfone herbicide intermediates by a reaction step comprising the oxidation of the hereinafter described corresponding sulfide herbicide intermediate using an aqueous solution of hydrogen peroxide.
• the improvement comprises maintaining during the reacting step or substantially throughout the entire time of the oxidation the concentration of the aqueous solution of hydrogen peroxide at a high concentration (above 70 percent by weight based upon the combined weight of the hydrogen peroxide and water in the reaction mixture) .
• a high concentration of the hydrogen peroxide is maintained throughout the reaction time period by the constant or periodic removal of water from the reaction mixture at such times or at such rates so as to not allow the concentration of the hydrogen peroxide to fall below 70 percent by weight.
• Water is removed from the reaction mixture of (1) sulfide reactant (2) a solvent that is not misicible with water (3) hydrogen peroxide and (4) water, preferably by the azeotropic distillation of water and solvent.
• the distillation is carried out at a temperature below about 100 ⁇ C, more preferably below about 90°C.
• the distillate of water and solvent can be separated and solvent returned to the reaction vessel by conventional techniques if necessary to maintain sufficient solvent in the reaction vessel.
• This invention relates to a process for preparing compounds having the structural formula
• R is (1) -COOR a wherein R a is ⁇ -Cg alkyl, preferably C.-C. alkyl, more preferably ethyl, n-propyl, or n-butyl; (2) C.-C. alkyl, preferably C.-C alkyl, more preferably methyl; (3) formyl or (4) -C(O) R wherein R is C.-C. alkyl, preferably methyl, most preferably R is -COOR wherein R is ethyl or n-propyl,
• R is hydrogen; halogen, preferably chlorine or bromine, more preferably chlorine; nitro; C -C_ alkyl, preferably methyl; C.-C alkoxy, preferably methoxy; or trifluoromethyl,most preferably R 1 i.s chlorine or nitro,
• R 2 i.s hydrogen; halogen, preferably chlorine;
• C.-C. alkoxy preferably methoxy or ethoxy
• -OCH 2 OC_H 5 preferably methyl
• -OCH 2 OCH 3 preferably methyl
• C.-C. alkyl preferably methyl
• a substituted C.-C. alkyl group preferably C. -C haloalkyl, more preferably chloromethyl or trifluoromethyl
• -CH 2 OCH_ -CH 2 OC 2 H 5 ; or -C(0)OR c wherein R c is C 1 ⁇ C 4 alkyl
• R is C,-C. alkyl, preferably methyl or ethyl or
• R, R 1, R2 and R3 are as defi.ned with hydrogen peroxide under conditions defined herein.
• the reacting step must be (1) run in a solvent that is immiscible with water and which has an azeotroping temperature with water of less than 100 ⁇ C; preferably less than 90°C, and (2) carried out the reacting step while the concentration of the hydrogen peroxide is maintained at a concentration of above 70 percent by weight (preferably 90 percent by weight) based upon the weight of the hydrogen peroxide and any water present in the reaction mixture.
• Toluene, xylene and ethylene dichloride are the preferred solvents.
• the process of this invention can be better understood by considering the preceeding discussion of the process of this invention and the following specific examples.
• This example teaches the preparation of the n-propyl ester of 2-nitro-4-methylsulfonyl benzoic acid by the oxidation of the n-propyl ester of 2-nitro-4-methylthio- benzoic acid by the process of this invention.
• the temperature was maintained at 90°C - 100°C during the addition. Water was removed from the reaction mixture by azeotropic distillation and drained periodically from the Dean-Stark trap where it had collected. The reaction was monitored by a Hewlitt-Packard Mode 1090 high performance liquid chromatograph with ultraviolet detector and the oxidation reaction was determined to be complete about 1 hour after all the hydrogen peroxide was added.
• the prepared n-propyl ester of 2-nitro-4-methyl- sulfonyl benzoic acid was not isolated but instead it was hydrolyzed to 2-nitro-4-methylsulfonyl benzoic acid for recovery.
• To the same reaction flask was charged 290 g water and 34 g 50% sodium hydroxide solution (17 g, 0.42 mole) .
• the mixture was heated to 25°C - 30 ⁇ C and held for six hours to hydrolyze the ester.
• the aqueous phase was cooled to 5°C - 10°C and 80 g of 25% sulfuric acid (20 g, 0.2 mole) was slowly added with agitation.
• the product was filtered and dried to give 43.0 g of solids.
• the purity of the 2-nitro-4-methysulfonyl benzoic acid was 92.7% by weight when compared to an anayltical reference standard.
• the yield was about 66% from the n-propyl ester of 2-nitro-4- methylthiobenzoic acid to the 2-nitro-4-methylsulfonylbenzoic acid.
• This example teaches the. preparation of the n-propyl ester of 2-chloro-4-methylsulfonyl benzoic acid by the oxidation of the n-propyl ester of 2-chloro-4-methylthio ⁇ benzoic acid by the process of this invention.
• the temperature was maintained at 90 ⁇ C - 100 ⁇ C during the addition. Water was removed from the reaction mixture by azeotropic distillation and drained periodically from the Dean-Stark trap where it had collected. The reaction was monitored by a Hewlitt-Packard Mode 1090 high performance liquid chromatograph and the oxidation reaction was determined to be complete about 1 hour after completion of the addition of the hydrogen peroxide. The concentration of the hydrogen peroxide aqueous solution was increased to over 70 percent by weight a few minutes after the start of the addition and was maintained at this concentration throughout the reaction time period.
• the prepared n-propyl ester of 2-chloro-4-methyl- sulfonyl benzoate was not isolated but instead hydrolyzed to 2-chloro-4-methylsulfonyl benzoic acid for recovery.
• To the reaction flask was charged 230 g water and 28 g 50% sodium hydroxide solution (14 g, 0.35 mole). The mixture was heated to 50°C and held for two hours to hydrolyze the ester. The aqueous phase was cooled to 5°C - 10°C and 40 g of 37% hydrochloric acid (14.8 g, 0.4 mole) was slowly added with agitation. The product was filtered and dried to give 51.5 g of solids.
• the purity of the 2-chloro-4-methylsulfonyl benzoic acid was 98.3 percent by weight when compared to an analytical reference standard.
• the yield was about 90% from the n-propyl ester of 2-chloro-4-methyl-thiobenzoic acid to the 2-chloro-4-methylsulfonylbenzoic acid.

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• 1990
  • 1990-10-15 US US07/599,203 patent/US5055605A/en not_active Expired - Fee Related
• 1991
  • 1991-10-14 ZA ZA918159A patent/ZA918159B/xx unknown
  • 1991-10-15 TW TW080108155A patent/TW215433B/zh active
  • 1991-11-27 WO PCT/US1991/007670 patent/WO1993011102A1/en not_active Ceased

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