m-Chloroperbenzoic acid → 3-Dichloromethylsulfinyl-7-fluoro-1-methyl-4-quinolone

Participants

Reaction Steps

665 mg (2.276 mmol) of the 3-dichloromethylthio-7-fluoro-1-methyl-4-quinolone (Compound 2, FIG. 1), as prepared in Step A, was dissolved in 20 ml of DCM at 0° C. to form a solution. To this solution was added 505.7 mg (2.345 mmol) of 80% MCPBA to form a mixture. This stirred mixture was then allowed to warm to room temperature and was stirred for 1 hour. An additional 25 mg of MCPBA was added and the mixture and stirred for 1 hour. The mixture was washed with 5% aqueous Na2CO3. The aqueous layer was extracted with DCM, and the combined DCM extracts were dried over anhydrous Na2SO4 and concentrated. The residue was chromatographed on silica gel with hexane-ethyl acetate (gradient 4:1,2:1,1:1) to give 352 mg (50%) of the product (Compound 3, FIG. 1) as a white solid, that was approximately 98% pure according to 1H NMR, CDCl3; d=3.96 s, 3H, N—CH3; 7.09 s, 1H, CHCl2; 7.22 dd, 1H, J=10.2 & 2.4 Hz, H at C8, 7.27 ddd, 1H, J=9.0, 7.6 & 2.2 Hz, H at C6; 8.03 s, 1H, H at C2; 8.43 dd, 1H, J=8.8 & 6.1 Hz, H at C5. This white solid product was further purified by recrystallization from methanol to give 252 mg of white crystals.

Provenance & Evidence