Isobutylene oxide → Benzyl 1-(2-hydroxy-2-methylpropyl)-5-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carboxylate

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Reaction Conditions

Reaction Steps

To a stirring suspension of benzyl 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carboxylate (3380 mg, 11 mmol) in chlorobenzene (30 mL) at 10° C. under nitrogen was added trimethylaluminum (16 mL, 33 mmol, 2M in toluene). Internal temperature reached 27° C. At 25° C., 1,2-epoxy-2-methylpropane (1000 mg, 16 mmol) was added. The reaction mixture was stirred for 3 h at 25° C., and then diluted with THF (500 mL). The resultant was chilled to 10° C., and sodium sulfate decahydrate (2 g) was added. After 1 hr, another 2 g of sodium sulfate decahydrate added. After 2 h, the gel was filtered through a bed of celite and washed with EtOAc (3×100 mL). The filtrate was then washed with aq. 1 M HCl (50 mL) and brine. The organic layer was dried over MgSO4. and concentrated. The residue was purified on 120 g silica chromatography (30>90% EtOAc/hex). To give the title compound (1.11 g, 27% yield) as an amorphous solid. MS (ESI pos. ion) m/z: 381 (MH+). Calc'd exact mass for C22H24N2O4 380.

Provenance & Evidence