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: 5898074
    Abstract: The present invention provides a process for preparing 2-(methylthio)-5-(trifluoromethyl)-1,3,4-thiadiazole. The process includes the steps of reacting methyldithiocarbazinate with a molar excess of trifluoroacetic acid and recovering the excess trifluoroacetic acid.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: April 27, 1999
    Assignees: Bayer Corporation, Bayer Aktiengesellschaft
    Inventors: Vidyanatha A. Prasad, Achim Noack
  • Patent number: 5895818
    Abstract: The present invention relates to a process for making N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-trifluoromethyl)-1,3,4-thiadiaz ol-2-yl)oxy!acetamide in an aprotic, aromatic solvent. The process includes the steps of: (a) reacting 2-(methylsulfonyl)-5-(trifluoromethyl)-1,3,4-thiadiazole with N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamide in the presence of an aprotic, aromatic solvent to form an aqueous phase and an organic phase; (b) acidifying the phases, (c) separating the phases; and (d) recovering the N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-trifluoromethyl)-1,3,4-thiadiaz ol-2-yl)oxy!acetamide from the organic phase.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: April 20, 1999
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis, Daniel M. Wasleski, Jacqueline M. Applegate, Klaus Jelich
  • Patent number: 5877339
    Abstract: Disclosed herein is an aqueous process for preparing high yields of methyl dithiocarbazinate by reacting carbon disulfide and hydrazine in an effective ratio, in an aqueous medium to form hydrazinium dithiocarbazinate salt followed by methylating the hydrazinium dithiocarbazinate with methyl bromide.
    Type: Grant
    Filed: November 7, 1996
    Date of Patent: March 2, 1999
    Assignee: Bayer Corporation
    Inventors: Daniel M. Wasleski, Peter E. Newallis, Dennis E. Jackman, David T. Erdman, Jeffrey D. Macke, Vidyanatha A. Prasad, Vijay C. Desai
  • Patent number: 5856499
    Abstract: The present invention provides a process for making thiadiazole sulfones. The present process is used to make 2-(methylsulfonyl)-5-(trifluoromethyl)-1,3,4-thiadiazole. 2-(Methylsulfonyl)-5-(trifluoromethyl)-1,3,4-thiadiazole is made using catalytic oxidation in the presence of a suitable oxidizing agent. The catalyst used for the oxidation reaction is glacial acetic acid.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: January 5, 1999
    Assignees: Bayer Corporation, Bayer Aktiengesellschaft
    Inventors: Vidyanatha A. Prasad, Jacqueline M. Applegate, Klaus Jelich, Achim Noack
  • Patent number: 5852202
    Abstract: The present invention relates to a process for isolating N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-trifluoromethyl)-1,3,4-thiadiaz ol-2-yl)oxy!acetamide from a solution of N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-trifluoromethyl)-1,3,4-thiadiaz ol-2-yl)oxy!acetamide in an aprotic, aromatic solvent. The process includes the steps of: (a) removing the solvent from the solution to form a substantially solvent-free material; (b) melting the material from step (a) to form a molten material; and (c) isolating N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-trifluoromethyl)-1,3,4-thiadiaz ol-2-yl)oxy!acetamide from the molten material by flaking.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: December 22, 1998
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Jonathan D. Spicher, Warren A. Fischer
  • Patent number: 5831112
    Abstract: The invention is directed to a process for producing a stable, low odor S,S,S-tributylphosphorotrithioate having a level of dibutyl disulfide of 0.3% by weight or less. The process broadly includes the steps ofa) reacting S,S,S-tributylphosphorotrithioite with an oxidizing agent to produce a crude S,S,S-tributylphosphorotrithioate,b) treating the crude product with sodium bisulfite to decompose any excess oxidizing agent,c) adding a caustic solution having a caustic concentration of from 25 to 50% by weight directly to the reaction mixture of step b), the addition of said caustic solution being stopped once the total caustic concentration is less than 10% by weight and once the pH is constant, andd) phase separating S,S,S-tributylphosphorotrithioate from the mixture of step c).
    Type: Grant
    Filed: June 20, 1997
    Date of Patent: November 3, 1998
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis
  • Patent number: 5808152
    Abstract: The present invention relates to a process for making N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamide. The process includes the steps of (a) reacting 2-chloro-N-(4-fluorophenyl)-N-(1-methylethyl)acetamide with sodium formate to form a reaction mixture that contains N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamideformate; (b) adding an aprotic, aromatic solvent to the reaction mixture; (c) hydrolyzing the N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamideformate in the reaction mixture and (d) recovering N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamide from the organic phase.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: September 15, 1998
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Jacqueline M. Applegate, David T. Erdman, Peter E. Newallis
  • Patent number: 5808153
    Abstract: The present invention provides a process for converting N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamide acetate to N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamide. The process includes the step of hydrolyzing N-(4-fluorophenyl)-2-hydroxy-N-(1-methylethyl)acetamide acetate with water or an aqueous alkali in the presence of an aprotic, aromatic solvent.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: September 15, 1998
    Inventor: Vidyanatha A. Prasad
  • Patent number: 5792872
    Abstract: The present invention relates to a process for making N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-(trifluoromethyl)-1,3,4-thiadia zol-2-yl)oxy!acetamide, which process includes the steps of reacting 2-(methylsulfonyl)-5-(trifluoromethyl)-1,3,4,-thiadiazole with N-(4-fluorophenyl)-2-hydroxy-N(1-methylethyl)acetamide in an aprotic, aromatic solvent with aqueous alkali to form an aqueous phase and an organic phase, separating the aqueous and organic phases and recovering the N-(4-fluorophenyl)-N-(1-methylethyl)-2-?(5-(trifluoromethyl)-1,3,4-thi adiazol-2-yl)oxy!acetamide from the organic phase. A preferred solvent and aqueous alkali are toluene and aqueous sodium hydroxide, respectively.
    Type: Grant
    Filed: December 12, 1997
    Date of Patent: August 11, 1998
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Jacqueline M. Applegate, Daniel M. Wasleski, Klaus Jelich
  • Patent number: 5543543
    Abstract: Disclosed herein is a process for preparing a phosphorodichloridodithioate comprising reacting a mercaptan, phosphorus trichloride, thiophosphoryl chloride and sulfur in the presence of a base catalyst.
    Type: Grant
    Filed: May 17, 1995
    Date of Patent: August 6, 1996
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis, Emerson L. Foote, Jr.
  • Patent number: 5527939
    Abstract: Disclosed herein is an improved process for preparing a phosphorodihalodithioate comprising reacting a mercaptan with a thiophorphoryl halide in the presence of a catalyst, the improvement comprising a catalytic amount of a tertiary amine catalyst.
    Type: Grant
    Filed: April 28, 1994
    Date of Patent: June 18, 1996
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis
  • Patent number: 5523449
    Abstract: Disclosed herein is a process for preparing a phosphorodichloridodithioate comprising reacting a mercaptan with a phosphorus trichloride and sulfur in the presence of an amine catalyst.
    Type: Grant
    Filed: May 17, 1995
    Date of Patent: June 4, 1996
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis, Emerson L. Foote, Jr.
  • Patent number: 5466852
    Abstract: S,S,S-tributylphosphorotrithioite is oxidized with a perborate or percarbonate at a pH of from about 6 to about 12 and at a temperature of from about 40.degree. to about 65.degree. C. Sodium perborate is a particularly preferred oxidizing agent. The product S,S,S-tributylphosphorotrithioate may be recovered by simple phase separation.
    Type: Grant
    Filed: August 30, 1994
    Date of Patent: November 14, 1995
    Assignee: Bayer Corporation
    Inventors: Vidyanatha A. Prasad, Peter E. Newallis
  • Patent number: 5464600
    Abstract: Disclosed herein is an improved process for preparing a thiophosphoryl chloride comprising reacting sulfur with a phosphorous trichloride, the improvement comprising a catalytic amount of a tertiary amine catalyst.
    Type: Grant
    Filed: December 27, 1994
    Date of Patent: November 7, 1995
    Assignee: Bayer Corporation
    Inventors: Peter E. Newallis, Vidyanatha A. Prasad, Jacqueline M. Applegate
  • Patent number: 5440038
    Abstract: Substituted 4-amino-1,2,4-triazine-5-ones are purified to remove unwanted N-isomers by maintaining the crude product at a temperature of from about 55.degree. C. to about 70.degree. C. in the presence of a hydroxide, preferably an alkali metal hydroxide for at least 0.5 hour.
    Type: Grant
    Filed: December 7, 1993
    Date of Patent: August 8, 1995
    Assignee: Miles Inc.
    Inventors: Vidyanatha A. Prasad, David M. Mayes, Peter E. Newallis, Karl G. Steinbeck
  • Patent number: 5189195
    Abstract: Stable S,S,S-tributylphosphorotrithioate having reduced levels of the odorous by-product dibutyl disulfide is produced by adding a caustic solution having a concentration of less than 10% to crude S,S,S-tributylphosphorotrithioate until the pH remains constant. In a preferred embodiment, a solution of sodium hydroxide having a concentration of less than 10% is used in an amount such that at least 0.1 mole of sodium hydroxide is present for each mole of crude S,S,S-tributylphosphortrithioate.
    Type: Grant
    Filed: July 30, 1991
    Date of Patent: February 23, 1993
    Assignee: Miles Inc.
    Inventors: Peter E. Newallis, Vidyanatha A. Prasad, Edward R. Levy
  • Patent number: 4970320
    Abstract: X represents a halogen, phenyl, phenoxy or halophenoxy moiety, andn is an integer of from 0 to 5,is produced by reacting 1,2,4-triazole with an .alpha.-halo-.alpha.-phenoxy compound of the formula ##STR2## in which Y represents Br or Cl, in the presence of a tertiary amine and a water-immiscible organic solvent. The amine is liquid at ambient temperature, substantially water-insoluble in its free base form and water-soluble in salt form.
    Type: Grant
    Filed: January 24, 1990
    Date of Patent: November 13, 1990
    Assignee: Mobay Corporation
    Inventor: Vidyanatha A. Prasad
  • Patent number: 4228279
    Abstract: In the reaction of a halomethylbenzazamide with an O,O-di-lower alkyl-thiolphosphoric acid ester to form an ester in accordance with the equation ##STR1## in which Y is oxygen or sulfur, andM is an alkali metal or ammonium cation,the improvement which comprises starting the reaction at a pH from about 2.5 to 5.5, whereby the desired reaction product is produced in higher yield and assay.
    Type: Grant
    Filed: August 28, 1979
    Date of Patent: October 14, 1980
    Assignee: Mobay Chemical Corporation
    Inventors: Vidyanatha A. Prasad, James H. Vines
  • Patent number: 4154780
    Abstract: A process for the preparation of a dithiophosphoric acid diester-halide of the formula ##STR1## IN WHICH R.sup.1 is alkyl with 1 to 10 carbon atoms, aralkyl with 1 to 6 carbon atoms in the alkyl radical, or alkoxyalkyl or alkylthioalkyl with 1 to 5 carbon atoms in each alkyl radical,R.sup.2 is alkyl with 1 to 8 carbon atoms, andHal is halogen,Which comprises reacting an S-alkyl or S-aralkyl ester of a dithiophosphoric acid dihalide of the formula ##STR2## WITH ABOUT A 5 TO 300% MOLAR EXCESS OF AN ALCOHOL OF THE FORMULAR.sup.2 OHin the presence of about a 5 to 300% molar excess of a tertiary pyridine base or tertiary aralkyl-alkylamine at a temperature between about -10.degree. and +60.degree. C.
    Type: Grant
    Filed: March 31, 1977
    Date of Patent: May 15, 1979
    Assignees: Bayer Aktiengesellschaft, Mobay Chemical Corporation
    Inventors: Reimer Colln, Hermann Arold, Vidyanatha A. Prasad