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US 5,672,702 AGranted
Process for preparing 3 amino 1, 2, 4-benzotriazine dioxide
AssigneeSanofi
InventorRichard E. Philion
Life of this patent
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Abstract
Process of producing 3-amino-1,2,4-benzotriazine 1,4-dioxide by reacting benzofurazan-1 oxide with disodiumcyanamide under homogeneous conditions followed by allowing crystallization to occur in a buffered solution. In a preferred embodiment, the process comprises reacting benzofurazan-1 oxide with cyanamide and sodium hydroxide under homogeneous conditions followed by purification in a mixture of acetone and acetic acid.
Claims7
A process for the preparation of 3-amino-1,2,4-benzotriazine 1,4-dioxide comprising the steps of:
- a) adding a solution of benzofurazan-1 oxide in dimethylsulfoxide in a molar ratio of 1 to 3 to a solution of disodiumcyanamide in water in a molar ratio of 3 to 2 contained in a reaction vessel at a temperature of from about 55.degree. to 65.degree. C. to obtain the sodium salt of 3-amino-1,2,4-benzotriazine 1,4-dioxide as a precipitate;
- b) removing the precipitate and suspending it in excess water;
- c) adding about 3.5 mole equivalents of methanesulfonic acid to the suspension to obtain a solution;
- d) filtering the solution to remove acid insoluble impurities therefrom;
- e) charging the filtered solution into a buffered solution containing excess sodium acetate and allowing crystallization to occur;
- f) filtering and washing the crystalline particles with water;
- g) charging the washed crystalline particles back into said reaction vessel and stirring it with about five volume of water;
- and
- h) filtering the crystalline particles and rinsing them with acetone to obtain the purified 3-amino-1,2,4-benzotriazine 1,4-dioxide.
6 more elements
A process for the preparation of 3-amino-1,2,4-benzotriazine 1,4-dioxide comprising the steps of:
- a) adding a solution of benzofurazan-1 oxide in dimethylsulfoxide in a molar ratio of 1 to 3 to an aqueous solution of cyanamide and sodium hydroxide having a molar ratio of 3 to 6 at a temperature of from about 55.degree. C. to 65.degree. C. to obtain the sodium salt of 3-amino-1,2,4-benzotriazine 1,4-dioxide as a partial suspension/solution;
- b) diluting the partial suspension/solution with water in a volume ratio of about 1 to 6 thereby obtaining a solution containing base-insoluble impurities;
- c) filtering the solution to remove the base-insoluble impurities therefrom;
- d) neutralizing the solution with a slight excess of glacial acetic acid to obtain a crude crystalline mixture;
- e) cooling the crystalline mixture and collecting the solids by filtration in the form of a damp cake;
- f) adding, with stirring, a mixture of acetone and acetic acid in the ratio of about 88:
- 12;
- g) collecting the crystalline particles by filtration and rinsing them with the mixture of acetone and acetic acid having the ratio of about 88:
- 12, followed by rinsing with water;
- h) adding about five volumes of water to the crystalline particles to obtain a suspension;
- i) acidifying the suspension with methanesulfonic acid in a 3.5 mol equiv. ratio;
- j) collecting the suspended crystalline particles by filtration, charging them into a well-stirred dilute sodium acetate solution, and allowing them to microcrystallize to form an average particle size of less than 190 mm;
- and
- k) collecting the microcrystalline particles by filtration and rinsing them with water, followed by rinsing with acetone to obtain the purified 3-amino-1,2,4-benzotriazine 1,4-dioxide.
11 more elements
Dependencies are inferred from the claim text.