反应详情

5.8 g of methyl 1-benzyloxycarbonyl-2-(2,3-dibromopropionyl)-hexahydro-3-pyridazinecarboxylate (2 racemates) were stirred for 1 hour at room temperature with 15 ml of 45% hydrogen bromide solution in glacial acetic acid and the mixture was then evaporated. The resulting oily solid was washed with diethyl ether and then partitioned between dichloromethane and saturated aqueous sodium bicarbonate solution. The organic phase was separated, dried over sodium sulphate and evaporated. The residue was chromatographed on silica gel. Elution with tert.butyl methyl ether gave firstly 0.4 g (12%) of methyl 2-bromo-hexahydro-3-oxo-1H-pyrazolo[1,2-a]pyridazine-5-carboxylate (racemate A) in the form of a white solid of melting point 115°-117° C. (from ethyl acetate/hexane) and secondly 2.54 g (78%) of methyl 2-bromo-hexahydro-3-oxo-1H-pyrazolo[1,2-a]pyridazine-5-carboxylate (B) in the form of a white solid of melting point 109°-112° C. (from ethyl acetate/n-hexane).

1. customthe mixture was then evaporated
2. washThe resulting oily solid was washed with diethyl ether
3. custompartitioned between dichloromethane and saturated aqueous sodium bicarbonate solution
4. customThe organic phase was separated
5. dry with materialdried over sodium sulphate
6. customevaporated
7. customThe residue was chromatographed on silica gel
8. washElution with tert.butyl methyl ether