Hydrochloric Acid → 4-[3-[4-[2-(1,3-Dioxolan-2-yl)vinyl]phenyl]-3-oxopropyl]-5-methyl-2-phenyloxazole

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Reaction Steps

To a mixture of [(1,3-dioxolan-2-yl)methyl]triphenylphosphonium bromide (9.61 g) and N,N-dimethylformamide (DMF) (60 ml), sodium hydride (60% in oil, 0.9 g) was added, followed by stirring at room temperature for 20 minutes. To this mixture, 4-[3-(5-methyl-2-phenyl-4-oxazolyl)propionyl]benzaldehyde (6.50 g) was added, followed by stirring at room temperature for 4 hours. The reaction mixture was poured over ice water, neutralized with 2N HCl and then extracted with ethyl acetate. The ethyl acetate layer was washed with water, dried (MgSO4) and then concentrated under reduced pressure; the residue was subjected to silica gel column chromatography. From the fraction eluted with ethyl acetate-chloroform (1:100), 4-[3-[4-[2-(1,3-dioxolan-2-yl)vinyl]phenyl]-3-oxopropyl]-5-methyl-2-phenyloxazole was obtained as an oily substance, which was then dissolved in tetrahydrofuran (THF) (150 ml). After addition of palladium-carbon (5%, 3.0 g), the solution was subjected to catalytic hydrogenation at 1 atm and room temperature. After the catalyst was filtered off, the filtrate was concentrated under reduced pressure; the residue was subjected to silica gel column chromatography. From the fraction eluted with ethyl acetate-hexane (1:3), 4-[3-[4-[2-(1,3-dioxolan-2-yl)ethyl]phenyl]-3-oxopropyl]-5-methyl-2phenyloxazole (2.4 g, 30%) was obtained, which was then recrystallized from ether-isopropyl ether to yield colorless needles having a melting point of 89°-90° C.

Provenance & Evidence