Phosgene → 2H-Indazole, 3-chloro-2-(4-chloro-2-fluorophenyl)-4,5,6,7-tetrahydro-

Participants

Reaction Steps

One hundred parts of 2-(4-chloro-2-fluorophenyl)-1,2,4,5,6,7-hexahydro-3H-indazol-3-one was heated under a nitrogen atmosphere (nitrogen was slowly passed through the system at atmospheric pressure) in a 3-neck, round-bottomed flask, fitted with a mechanical stirrer, dry ice condenser, an addition funnel with a gas-inlet and dry ice condenser above it. Phosgene was condensed into the addition funnel from a pressurized cylinder, and 44 parts of phosgene was added dropwise over 2 hours, maintaining a temperature of 178°-180° in the reaction mixture for the first 11/2 hours and allowing it to fall to 135° during the last 1/2 hour. The dry ice in the condenser was removed and the excess phosgene was passed through a 10% sodium hydroxide solution as it evaporated. The reaction mixture was poured out into a pan and allowed to cool. There was obtained 100.6 parts of 2-(4-chloro-2-fluorophenyl)-3-chloro-4,5,6,7-tetrahydro-2H-indazole, m.p. 81°-85° (80.4% pure as determined by gas chromatography).

Provenance & Evidence