Selective chlorination of a 1-(2-fluorophenyl)-1,2,4-triazole
DCFirst Claim
1. A process for the chlorination of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole (the "2-fluorophenyl compound") in the 4-position of the phenyl ring which comprisesa) adding 0.8 to 1.6 molar equivalents of chlorine to a stirred slurry of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole in a solvent selected from acetonitrile, N,N-dimethylformamide, nitromethane, and nitrobenzene, at a temperature in the range of ambient to 50°
- C., at a rate such that the temperature does not exceed 50°
C., and continuing the stirring at 30 to 50°
C. for from one to ten hours;
b) for a period of from one to six hours, while maintaining the temperature at 30 to 50°
C., reducing the pressure in the reaction vessel so that the solvent refluxes and most of the hydrogen chloride by-product is driven off;
c) optionally, purging the reaction vessel with nitrogen to reduce the hydrogen chloride concentration in the reaction mixture to below 1%;
d) repeating steps a, b, and c two times;
e) recovering 1-(4-chloro-2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole.
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Abstract
A process is disclosed in which the 4-position of the 1-(2-fluorophenyl) group attached to a 4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole, an intermediate in the route to prepare the herbicide ethyl α-2-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl]-4-fluorobenzenepropanoate, is chlorinated in good yield. The process involves adding chlorine gas in three separate steps, with by-product hydrogen chloride being removed at the end of each chlorine addition step.
1 Citation
13 Claims
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1. A process for the chlorination of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole (the "2-fluorophenyl compound") in the 4-position of the phenyl ring which comprises
a) adding 0.8 to 1.6 molar equivalents of chlorine to a stirred slurry of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole in a solvent selected from acetonitrile, N,N-dimethylformamide, nitromethane, and nitrobenzene, at a temperature in the range of ambient to 50° - C., at a rate such that the temperature does not exceed 50°
C., and continuing the stirring at 30 to 50°
C. for from one to ten hours;b) for a period of from one to six hours, while maintaining the temperature at 30 to 50°
C., reducing the pressure in the reaction vessel so that the solvent refluxes and most of the hydrogen chloride by-product is driven off;c) optionally, purging the reaction vessel with nitrogen to reduce the hydrogen chloride concentration in the reaction mixture to below 1%; d) repeating steps a, b, and c two times; e) recovering 1-(4-chloro-2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole. - View Dependent Claims (2, 3, 4)
- C., at a rate such that the temperature does not exceed 50°
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5. A process for chlorination of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole at the 4-position of the phenyl ring which comprises the steps of:
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(a) adding chlorine to a mixture of 1-(2-fluorophenyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazole and a solvent, wherein said addition forms hydrogen chloride as a by-product; and (b) reducing the concentration of the hydrogen chloride by-product after said addition. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
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Specification