Benzamide → Methyl (5-methyl-2-phenyl-1,3-oxazol-4-yl)acetate

Participants

Reaction Conditions

Reaction Steps

A 500-ml 4-necked flask equipped with a mechanical stirrer, a thermometer, a Claisen head with a condenser and a receiver connected to a cold trap and a vacuum controller was charged with 52.26 g of crude methyl 4-bromo-3-oxovalerate (ca. 0.250 mol) and 46.5 g of benzamide. A vacuum of 400 mbar was applied and the suspension was stirred at 90° C. for 18 h. After ca. 3 h the suspension had become a clear orange oil. After cooling to rt 300 ml of methanol and 1.0 g of p-toluenesulfonic acid monohydrate were added and the brown solution was stirred at reflux (ca. 73° C.) for 1 h. After this time 50 ml of methanol were distilled off, 50 ml of methanol were added and the mixture was heated at reflux for additional 30 min. After cooling and rotary evaporation (50° C., 8 mbar, 30 min), the residue was treated under argon with 150 ml of toluene and 125 ml of sat. aqueous sodium bicarbonate solution. The resulting suspension was stirred in an ice bath for 1 h, the precipitated benzamide was filtered off with suction and the filter cake was washed twice with a small amount of ice-cold toluene and water. The combined aqueous phases were extracted in a separatory funnel with 100 ml of toluene. Thereafter the combined organic phases were washed twice with 30 ml, a total of 60 ml of deionized water, dried (Na2SO4) and rotary evaporated (50° C., 8 mbar,1 h) to give 49.22 g of crude Methyl 2-(5-methyl-2-phenyl-4-oxazolyl)acetate (theor. amount 57.81 g) as a yellow oil, which was used without purification in the next step.

Provenance & Evidence