Reaction #59657

Reaction equation

2-fluoro-4-methylsulfonylphenyl hydrazine

ethoxymethylene malononitrile

→

pyrazole

5-Amino-1-(2-fluoro-4-methanesulfonyl-phenyl)-1H-pyrazole-4-carbonitrile

Solvents

methanol

methanol

Conditions

Workup

1. 1
   Temperatureto maintain the reaction mixture at −10° to 0° C. with reactor jacket
2. 2
   Temperaturecooling
3. 3
   workup.ADDITIONAfter the addition
4. 4
   Temperatureheated
5. 5
   Temperatureto reflux for 5 hours, at which time the reaction mixture

Procedure

To a stirred suspension of 2-fluoro-4-methylsulfonylphenyl hydrazine (1) (4.0336 Kg; 1 eq) (commercially available from, e.g., Peakdale Molecular, Ltd.) in methanol (12.7723 Kg) was added a suspension of ethoxymethylene malononitrile (2.6564 Kg, 1.101 equivalents) in methanol (11.212 Kg) at a rate sufficiently slow to maintain the reaction mixture at −10° to 0° C. with reactor jacket cooling. After the addition had been completed, the reaction mixture was stirred for 1 hour at −6° C. and then heated to reflux for 5 hours, at which time the reaction mixture gave a pyrazole (3): hydrazine (1) HPLC peak area ratio of 105:1. Solvent (20.5153 Kg) was then distilled off the reaction mixture at atmospheric pressure, leaving a residue having less than 20% of the original volume. The resulting mixture was used directly in the next step.

Source