Trifluoroacetic acid → (R)-8-(5-bromo-2-fluoro-phenyl)-8-methyl-6,6-dioxo-6lambda6-thia-9-aza-spiro[4.5]dec-2-en-10-one

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Reaction Conditions

Reaction Steps

A mixture of (R)-8-(5-bromo-2-fluoro-phenyl)-9-(2,4-dimethoxy-benzyl)-8-methyl-6,6-dioxo-6λ6-thia-9-aza-spiro[4.5]dec-2-en-10-one (450 mg, 836 μmol, Eq: 1.00) and trifluoroacetic acid (9.53 g, 6.44 ml, 83.6 mmol, Eq: 100) was stirred at 23° C. After 1 hour trifluoromethanesulfonic acid (251 mg, 148 μl, 1.67 mmol, Eq: 2.0) was added and the dark red solution was stirred for 2 hours. Poured into 1 M Na2CO3-sol. and extracted twice with ethyl acetate. The combined organic layers were dried over Na2SO4, filtered and evaporated. The residue was chromatographed on 10 g silica gel with heptane/ethyl acetate 1:1 to give (R)-8-(5-bromo-2-fluoro-phenyl)-8-methyl-6,6-dioxo-6λ6-thia-9-aza-spiro[4.5]dec-2-en-10-one (340 mg, 788 μmol, 94.3% yield) as a white solid. MS (ISP): m/z=388.1 [M+H]+ and 390.2 [M+2+H]+.

Provenance & Evidence