Ethyl isocyanate → (+/-)-1-Ethyl-3-[6-fluoro-2,3-dihydro-2',4'-dioxospiro[4H-1-benzopyran-4,5'-thiazolidin]-8-yl]-urea

Participants

Reaction Conditions

Reaction Steps

268 mg of (±)-8-amino-6-fluoro-2,3-dihydrospiro[4H-1-benzopyran-4,5'-thiazolidine]-2',4'-dione were stirred in 2 ml of tetrahydrofuran with 100 μl of ethyl isocyanate at room temperature for 2.5 hours and the mixture was subsequently heated to 50° C. for an additional 2 hours. The liquid constituents were removed under reduced pressure, he residue was purified by chromatography on a silica gel column using hexane/ethyl acetate (1:2) for the elution, decolorized with active carbon and recrystallized from ethyl acetate/hexane. (±)-1-Ethyl-3-[6-fluoro-2,3-dihydro-2',4'-dioxospiro[4H-1-benzopyran-4,5'-thiazolidin]-8-yl]-urea was obtained in the form of colorless crystals of melting point 197°-199° C.

Provenance & Evidence