Allyl bromide → Methyl 2-(4-cyano-2-cyclopropyl-5-methyl-6-phenyl-1,3-benzoxazol-7-yl)pent-4-enate

Participants

Reaction Conditions

Reaction Steps

Methyl (4-cyano-2-cyclopropyl-5-methyl-6-phenyl-1,3-benzoxazol-7-yl)acetate (I-295) (2.215 g, 6.40 mmol) was dissolved in tetrahydrofuran (45 ml), and under nitrogen atmosphere at −78° C., potassium hexamethyldisilazide (0.5 M toluene solution) (19.2 ml, 9.59 mmol) was dropwise added, taking 10 minutes. After stirring at the same temperature for 1 hour, allyl bromide (847 μl, 9.59 mmol) was gradually added. The solution was gradually warmed up to 0° C., taking 1.5 hours, followed by stirring at the same temperature for 2 hours. At 0° C., aqueous saturated ammonium chloride solution was added to the solution, followed by stirring for 15 minutes. Under reduced pressure, THF was evaporated away, and the residue was extracted three times with ethyl acetate. The organic layers were combined, washed with saturated brine, and dried over anhydrous sodium sulfate. The insoluble matter was separated by filtration, the solvent was evaporated away, and the resulting residue was purified by middle-pressure liquid chromatography (eluent, n-hexane:ethyl acetate=4:1, v/v) to obtain the entitled compound (1.709 g, 69%) as a colorless gel. 410 mg (18.5%) of unreacted methyl (4-cyano-2-cyclopropyl-5-methyl-6-phenyl-1,3-benzoxazol-7-yl)acetate was recovered.

Provenance & Evidence