Ethyl Acetate → N-[5,6-dibromo-1H-indazol-3-yl]butanamide

Participants

Reaction Steps

12.2 cm3 of tetrabutylammonium fluoride as a 1M solution in tetrahydrofuran are added to 1 g of N-[5,6-dibromo-1-[[2-(trimethylsilyl)ethoxy]methyl]-1H-indazol-3-yl]butanamide, described previously, in 60 cm3 of tetrahydrofuran, and the mixture is refluxed for 18 hours; after cooling, 75 cm3 of ethyl acetate are added and the organic phase is washed successively with 100 cm3 of saturated sodium hydrogen carbonate solution and then with 75 cm3 of saturated sodium chloride solution. The organic phase is separated out after settling of the phases has taken place, dried over magnesium sulphate, filtered and concentrated to dryness under reduced pressure (2 kPa; 50° C.) to give 1.6 g of crude product, which is purified by chromatography under an argon pressure of 50 kPa, on a column of silica gel (particle size 40-60 μm; diameter 3.5 cm), eluting with a cyclohexane/ethyl acetate mixture (50/50 by volume). The fractions containing the expected product are combined and evaporated under reduced pressure (2 kPa; 50° C.) and the residue is taken up in 20 cm3 of diisopropyl ether, filtered off, washed with 2×10 cm3 of diisopropyl ether and dried (90 Pa; 45° C.) to give 460 mg of N-[5,6-dibromo-1H-indazol-3-yl]butanamide in the form of bluish crystals melting at 250° C.

Provenance & Evidence