Patents by Inventor Vidyanatha A. Prasad

Vidyanatha A. Prasad has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 7049456
    Abstract: The invention relates to a method of preparing O,O-dialkyl S-[2-(alkylthio)alkyl] phosphorodithioates by treating O,O-dialkyl dithiophosphoric acids with a base in the substantial absence of organic solvent to obtain O,O-dialkyl dithiophosphoric acid salts that are in turn treated with thioalcohol derivatives to form the O,O-dialkyl S-[2-(alkylthio)alkyl] phosphorodithioates.
    Type: Grant
    Filed: March 7, 2003
    Date of Patent: May 23, 2006
    Assignee: Bayer Cropscience LP
    Inventors: Vidyanatha A. Prasad, Robert D. Ingalls, Stephen C. Slahck, Christopher M. Tusa
  • Publication number: 20040176629
    Abstract: The invention relates to a method of preparing O,O-dialkyl S-[2-(alkylthio)alkyl]phosphorodithioates by treating -O,O-dialkyl dithiophosphoric acids with a base in the substantial absence of organic solvent to obtain O,O-dialkyl dithiophosphoric acid salts that are in turn treated with thioalcohol derivatives to form the O,O-dialkyl S-[2-(alkylthio)alkyl]phosphorodithioates.
    Type: Application
    Filed: March 7, 2003
    Publication date: September 9, 2004
    Inventors: Vidyanatha A. Prasad, Robert D. Ingalls, Stephen C. Slahck, Christopher M. Tusa
  • Publication number: 20040167348
    Abstract: The invention relates to a method of purifying an O,O-dialkyl S-[2-(alkylthio)alkyl] phosphorodithioate by purging a sample containing a volatile and the O,O-dialkyl S-[2-(alkylthio)alkyl] phosphorodithioate with a gas.
    Type: Application
    Filed: February 26, 2003
    Publication date: August 26, 2004
    Inventors: Vidyanatha A. Prasad, Robert D. Ingalls, Stephen C. Slahck, Christopher M. Tusa, Paul E. Nagy, Michael P. Newcomer, Donald K. Smith
  • Patent number: 6545172
    Abstract: A process for the production of methyl dithiocarbazinate includes the steps of providing a mixture comprising hydrazine, solvent, carbon disulfide and base; adding methyl bromide to the mixture; cooling the reaction mixture; and recovering methyl dithiocarbazinate. The methyl dithiocarbazinate may be recovered by filtering the reaction mixture to yield a solid methyl dithiocarbazinate retentate and a liquid filtrate; acidifying the filterate with a mineral acid; and adding methyl isobutylketone to the acidified filterate.
    Type: Grant
    Filed: April 18, 2002
    Date of Patent: April 8, 2003
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich, Dennis E. Jackman
  • Patent number: 6437189
    Abstract: The present invention provides a process for making sulfoxides from sulfides. The process includes the step of selectively oxidizing a sulfide utilizing a perborate or a percarbonate as an oxidizing agent.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: August 20, 2002
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis
  • Patent number: 6251350
    Abstract: The present invention relates to an improved process for the preparation of thiophosphoryl chloride which is useful as an intermediate for the synthesis of insecticidally active compounds. The improvement comprises the presence in the reaction mixture of a catalytic amount of a nitroxide free radical of the following general formula: wherein R1, R2, R3 and R4 represent an alkyl group.
    Type: Grant
    Filed: June 21, 1999
    Date of Patent: June 26, 2001
    Assignee: Bayer Corporation
    Inventors: Jacqueline M. Applegate, Peter E. Newallis, Vidyanatha A. Prasad
  • Patent number: 6197971
    Abstract: The present invention relates to a process for manufacturing substituted triazolinones, which are intermediates in the preparation of herbicidally active compounds. In particular, this invention relates to the alkylation of a non-alkylated triazolinone intermediate product, wherein the improvement comprises conducting the alkylation reaction under pH controlled conditions. In a preferred embodiment, the invention relates to the preparation of a 5-alkoxy(or aryloxy)-2,4-dihydro-3H-1,2,4-triazol-3-one, and the alkylation of this non-alkylated triazolinone intermediate product, to produce a 5-alkoxy(or aryloxy)-4-alkyl-2,4-dihydro-3H-1,2,4-triazol-3-one.
    Type: Grant
    Filed: December 27, 1999
    Date of Patent: March 6, 2001
    Assignee: Bayer Corporation
    Inventors: Shekhar V. Kulkarni, Vidyanatha A. Prasad, Vijay C. Desai, Eric Rivadeneira, Klaus Jelich
  • Patent number: 6160125
    Abstract: The present invention relates to a process for manufacturing sulfonylaminocarbonyl triazolinones, which are herbicidally active compounds. In particular, this invention relates to the reaction of a substituted triazolinone with a sulfonyl isocyanate, wherein the improvement comprises conducting this reaction in the presence of xylene as solvent.
    Type: Grant
    Filed: December 27, 1999
    Date of Patent: December 12, 2000
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich
  • Patent number: 6147222
    Abstract: The present invention relates to a process for manufacturing sulfonylaminocarbonyl triazolinones and salts thereof, which are herbicidally active compounds, wherein the improvement comprises conducting the conversion reaction of the sulfonylaminocarbonyl triazolinone to a salt thereof under pH controlled conditions. In particular, this invention relates to the conversion of a substituted triazolinone to a sulfonylaminocarbonyl triazolinone, and without the isolation of this intermediate product, the sulfonylaminocarbonyl triazolinone is then converted to a salt thereof.
    Type: Grant
    Filed: December 27, 1999
    Date of Patent: November 14, 2000
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich
  • Patent number: 6147221
    Abstract: The present invention relates to a process for manufacturing sulfonylaminocarbonyl triazolinones and salts thereof, which are herbicidally active compounds, wherein the process does not require isolation of the intermediate product. In particular, this invention relates to the conversion of a substituted triazolinone to a sulfonylaminocarbonyl triazolinone, and without the isolation of this intermediate product, the sulfonylaminocarbonyl triazolinone is then converted to a salt thereof.
    Type: Grant
    Filed: December 27, 1999
    Date of Patent: November 14, 2000
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Shekhar V. Kulkarni, Eric Rivadeneira, Vijay C. Desai
  • Patent number: 6127566
    Abstract: The present invention provides a continuous process for making O,O-dimethyl phosphoroamidothioate. In accordance with this process, O,O-dimethyl phosphorochloridothioate is reacted with ammonia and sodium hydroxide; addition of the sodium hydroxide controls the pH of the reaction mixture. The formed reaction mixture contains an aqueous phase and an organic phase. The organic phase of the reaction mixture is separated from the aqueous phase; a second organic phase is solvent extracted from the aqueous phase; and the resultant O,O-dimethyl phosphoroamidothioate is isolated from the combined organic phases via vacuum solvent stripping. In an embodiment of the present invention, the reaction of O,O-dimethyl phosphorochloridothioate with ammonia and sodium hydroxide is carried out in the presence of a solvent.
    Type: Grant
    Filed: September 16, 1998
    Date of Patent: October 3, 2000
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Donald K. Smith, David L. Meyer, Jonathan D. Spicher, Scott P. Hensley
  • Patent number: 6075157
    Abstract: The present invention provides a method for making O,S-dimethyl phosphoramidothioate. In accordance with this process, O,O-dimethyl phosphoramidothioate is isomerized in the presence of dimethyl sulfate to form a reaction mixture; the reaction mixture is then passed through a wiped film evaporator at a temperature of from about 55.degree. C. to about 120.degree. C. and a pressure of from about 3 to about 10 mm Hg, with the distillate containing O,S-dimethyl phosphoramidothioate, unreacted O,O-dimethyl phosphoramidothioate and by-products, and the residue containing O,S-dimethyl phosphoramidothioate in an amount greater than the amount of O,S-dimethyl phosphoramidothioate contained in the reaction mixture prior to distillation.
    Type: Grant
    Filed: August 17, 1998
    Date of Patent: June 13, 2000
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich
  • Patent number: 6034245
    Abstract: The present invention provides a process for making 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole. The process includes the steps of reacting methyidithiocarbazinate with trifluoroacetic acid, in the absence of phosphorus trichloride, to form a mixture of 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole and 2,5-bis-(methylthio)-1,3,4-thiadiazole. Further, the process of the present invention includes selectively removing the 2,5-bis-(methylthio)-1,3,4-thiadiazole by acidifying the reaction mixture, and then separating the aqueous and organic phases.
    Type: Grant
    Filed: December 18, 1998
    Date of Patent: March 7, 2000
    Assignees: Bayer Corporation, Bayer Aktiengesellschaft
    Inventors: Vidyanatha A. Prasad, Thomas Schmidt, Peter E. Newallis
  • Patent number: 6031108
    Abstract: The present invention provides a process for making thiadiazole sulfones. In particular, the present process is used to make 2-(methylsulfonyl)-5-(trifluoromethyl)-1,3,4-thiadiazole using catalytic oxidation in the presence of a suitable oxidizing agent. The catalyst system used for the oxidation reaction is a mixture of glacial acetic acid and a tungsten catalyst. The tungsten catalyst is preferably selected from the group consisting of sodium tungstate, potassium tunstate, and tungstic acid.
    Type: Grant
    Filed: September 16, 1998
    Date of Patent: February 29, 2000
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich, Joe J. Hanson
  • Patent number: 6025514
    Abstract: Disclosed herein is a process for preparing high yields of methyl dithiocarbazinate by reacting carbon disulfide, hydrazine and a base in an aqueous medium, in an effective ratio to form a dithiocarbazinate salt followed by methylating the dithiocarbazinate salt with methyl bromide.
    Type: Grant
    Filed: September 21, 1998
    Date of Patent: February 15, 2000
    Assignee: Bayer Corporation
    Inventors: Dennis E. Jackman, David T. Erdman, Peter E. Newallis, Daniel M. Wasleski, Vijay C. Desai, Jeffrey D. Macke, Vidyanatha A. Prasad
  • Patent number: 6005114
    Abstract: The present invention provides a process for making 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole. The process includes the steps of reacting methyldithiocarbazinate with trifluoroacetic acid to form a mixture of 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole and 2,5-bis-(methylthio)-1,3,4-thiadiazole and selectively removing the 2,5-bis-(methylthio)-1,3,4-thiadiazole by acidifying the mixture.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: December 21, 1999
    Assignees: Bayer Corporation, Bayer Aktiengesellschaft
    Inventors: Vidyanatha A. Prasad, Thomas Schmidt, Peter E. Newallis
  • Patent number: 5965737
    Abstract: The present invention provides a process for making thiadiazole sulfones. In particular, the present process is used to make 2-(methyl-sulfonyl)-5-(trifluoromethyl)-1,3,4-thiadiazole using catalytic oxidation in the presence of a suitable oxidizing agent. A preferred oxidizing agent is hydrogen peroxide. The catalyst system used for the oxidation reaction is a mixture of boric acid and glacial acetic acid. The molar ratio of glacial acetic acid to 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole is from about 0.1:1 to about 0.5:1.
    Type: Grant
    Filed: February 17, 1999
    Date of Patent: October 12, 1999
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Joe J. Hanson, Klaus Jelich
  • Patent number: 5922896
    Abstract: The present invention provides a method for making O,S-dimethyl phosphoramidothioate. In accordance with the present process, O,O-dimethyl phosphoramidothioate is isomerized in the presence of a catalyst at a temperature of from about 35.degree. C. to about 45.degree. C. to form a mixture containing O,S-dimethyl phosphoramidothioate and the resultant mixture is lagered at a temperature of from about 35.degree. C. to about 45.degree. C. for about 3 to 6 hours. The total time for both steps is at least about 4 hours.
    Type: Grant
    Filed: December 10, 1997
    Date of Patent: July 13, 1999
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich, Donald K. Smith
  • Patent number: 5922404
    Abstract: The present invention relates to an integrated process for synthesizing dimethyl (2,2,2-trichloro-1-hydroxyethyl)-phosphonate and a process for impregnating the dimethyl (2,2,2-trichloro-1-hydroxyethyl)-phosphonate on to inert carrier granules. The process involves adding dimethyl phosphite to a reaction mixture containing chloral under anhydrous, inert conditions. The molar ratio of chloral to dimethyl phosphite used in the reaction mixture is from about 1.0:1.0 to about 1.1:1.0. The impregnation process involves transferring molten dimethyl (2,2,2-trichloro-1-hydroxyethyl)-phosphonate into a process vessel and discharging weighed aliquots into a formulation vessel to form a granular product containing dimethyl (2,2,2-trichloro-1-hydroxyethyl)-phosphonate.
    Type: Grant
    Filed: September 29, 1997
    Date of Patent: July 13, 1999
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Klaus Jelich, Christopher M. Tusa, Daniel E. Terry, Stephen C. Slahck, Scott P. Hensley
  • Patent number: 5905157
    Abstract: The present invention provides a process of making 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole. The process includes the steps of (a) reacting methyldithiocarbazinate with a molar excess of trifluoroacetic acid; and (b) removing the water and excess trifluoroacetic acid. Water and excess trifluoroacetic acid are preferably removed via distillation.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: May 18, 1999
    Assignees: Bayer Corporation, Bayer Aktiengesellschaft
    Inventors: Vijay C. Desai, Peter E. Newallis, Vidyanatha A. Prasad, Herman Seifert