Trifluoroacetic acid → (4r,7s)-2-(2,4-Difluoro-phenyl)-7,8,8-trimethyl-1,2,4,5,6,7-hexahydro-4,7-methano-indazol-3-one

Participants

Reaction Conditions

Reaction Steps

Trifluoroacetic acid (80 mL) was added to a solution of crude N′-(2,4-difluoro-phenyl)-N′-((1S,4S)-4,7,7-trimethyl-3-oxo-bicyclo[2.2.1]heptane-2-carbonyl)-hydrazinecarboxylic acid tert-butyl ester (˜100 mmol) in dichloromethane (80 mL) at 0° C. The reaction mixture was stirred at 0° C. for 15 min, and then at room temperature for 4 h. The solvent was evaporated. The residue was taken up in dichloromethane (500 mL) and washed with water (4×600 mL) adding brine to help separate the layers when necessary. The solution was further washed with brine (250 mL), dried (magnesium sulfate), filtered, and evaporated. The solids were triturated with 10% dichlormethane/hexanes, filtered, washed with 5% dichloromethane/hexanes and then hexanes, stored over a weekend in the freezer, and then dried under high vacuum to give (4R,7S)-2-(2,4-difluoro-phenyl)-7,8,8-trimethyl-1,2,4,5,6,7-hexahydro-4,7-methano-indazol-3-one (25.71 g, 84%) as a light brown solid.

Provenance & Evidence