(R)-4-Phenyl-3-(1,2-propadienyl)-2-oxazolidinone (CAS NO.: ) could be produced through the following synthetic routes.

A. (R)-4-Phenyl-3-(2-propynyl)oxazolidin-2-one (CAS NO.: )(2). A flame-dried, 500-mL, round-bottomed flask equipped with a magnetic stirbar and a rubber septum fitted with a nitrogen inlet is charged with 9.90 g (61 mmol) of (R)-4-phenyl-2-oxazolidinone and 200 mL of anhydrous tetrahydrofuran (THF) under a nitrogen atmosphere. hydride (NaH) (2.90 g, 60% w/w in mineral oil, 1.20 equiv, 73 mmol) is added in small portions, and the resulting white slush is stirred for 1 hr at room temperature before carefully adding 8.00 mL of a solution of propargyl bromide in toluene (80% w/w in toluene, 72 mmol, 1.18 equiv) dropwise over ca. 10 min via syringe. Precipitation of sodium bromide is observed and does not affect the progress of the reaction. The reaction mixture is stirred at room temperature for 24 hr and then concentrated by rotary evaporation under reduced pressure. The residue is dissolved in 100 mL of anhydrous ether and filtered through a small bed of Celite washing with 1:1 ethyl acetate-hexane. The filtrate is concentrated by rotary evaporation, and the resulting residue is purified using silica gel column chromatography (gradient eluent with 0-33% ethyl acetate-hexane) to give 5.71-6.09 g (47-50%) of the desired propargyl amide 2 as a lightly yellow-colored oil.

B. (R)-4-Phenyl-3-(1,2-propadienyl)-2-oxazolidinone (CAS NO.: )(3). A flame-dried, 500-mL, round-bottomed flask equipped with a magnetic stirbar and a rubber septum fitted with a nitrogen inlet is charged with a solution of 6.67 g (33 mmol) of propargyl amide 2 in 300 mL of anhydrous THF. tert-butoxide (1.26 g, 11 mmol, 0.33 equiv) is added in portions to the reaction mixture over ca. 10 min. The reaction mixture is stirred at room temperature for 24 hr and the progress of the reaction is monitored by TLC (elution with 50% ethyl acetate-hexane) and 1H NMR analysis. Upon completion of the reaction, the solvent is removed by rotary evaporation under reduced pressure. The resulting crude residue is dissolved in 50 mL of ethyl acetate and vacuum filtered through a small bed of silica gel. The solids are washed with two 40-mL portions of 25-50% ethyl acetate-hexane, and the filtrate is then concentrated by rotary evaporation. The residue is purified using silica gel column chromatography (gradient elution with 0% to 25% ethyl acetate-hexanes) to give 1.41-1.59 g (38-41%) of the desired allenamide 3 as a yellow brownish-red oil.