1-Chloroethyl chloroformate → 1,1-Diphenyltetrahydro-1H-oxazolo[3,4-a]pyrazin-3(5H)-one

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Reaction Steps

Hexahydro-7-[(4-methylphenyl)methyl]-1,1-diphenyl-3H-oxazolo[3,4-a]pyrazin-3-one (65 g, 0.16 mol) was dissolved in 1,2-dichloroethane (300 mL). 1-Chloroethyl chloroformate (22 mL, 0.2 mol) was added thereto, and the mixture was warmed and refluxed for 3 hours. The solvent was distilled off under reduced pressure, and then methanol (300 mL) was added thereto. The mixture was warmed and refluxed for 3 hours. The solvent was distilled off under reduced pressure, and to the residue was added ethyl acetate (500 mL) to obtain powder. The obtained powder was collected by filtration, washed with ethyl acetate, and dried under reduced pressure. To the obtained powder (54 g) were added an aqueous saturated sodium hydrogen carbonate solution (500 mL) and ethyl acetate (500 mL), and the process of phase separation was performed. The resulting organic layer was washed with an aqueous saturated sodium hydrogen carbonate solution (400 mL) and dried over magnesium sulfate. The solvent was distilled off under reduced pressure. The residue was recrystallized from diethyl ether and the resulting crystals (42 g) were recrystallized from ethyl acetate again to obtain the title compound (38 g, yield 78%). 1H NMR of the above obtained compound corresponded with the compound obtained in Reference Example 2.

Provenance & Evidence