Hydrochloric Acid → 1-Benzyl-4-ethynyl-3-(1-hydroxyethyl)-2-azetidinone

Participants

Reaction Steps

To a solution of 2.054 g (5.0 mmol) of 3-benzylamino-2-(1-hydroxyethyl)-5-trimethylsilyl-4-pentinic acid phenylthio ester dissolved in 40 ml of THF was added 3 ml of 4N potassium hydroxide and the mixture was stirred at room temperature for 3 hours. The resultant was neutralised with 2N hydrochloric acid and extracted with ethyl acetate six times while conducting salting out. The extract was dried with anhydrous magnesium sulfate and concentrated. To the concentrate were added 250 ml of acetonitrile and then 1.57 g (6.0 mmol) of triphenylphosphine and the mixture was vigorously stirred under reflux condition, to which a solution of 1.32 g (6.0 mmol) of 2,2'-dipyridyldisulfide in 50 ml of acetonitrile was added dropwise for 40 minutes. After reflux for 1 hour, the reaction solution was concentrated and purified twice with 50 g of silica-gel chromatography (developer methylene chloride→diethyl ether) and then with 50 g of silica-gel chromatography (developer hexane:diethyl ether 1:4) to give 801 mg of trans-form and 62 mg of cis-form of 1-benzyl-4-ethynyl-3-(1-hydroxyethyl)-2-azetidinone.

Provenance & Evidence