Diisopropylamine → N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-hydroxypropyl)-azetidin-2-one

Participants

Reaction Steps

To a flame dried, 50 ml, 3-neck flask fitted with a N2 inlet, magnetic stirrer, addition funnel, and serum cap are added anhydrous tetrahydrofuran (THF) (10.5 ml) and diisopropyl amine (0.579 ml, 4.13 mmol). The solution is cooled in an ice-methanol bath under N2 and treated with 2.4N n-butyl lithium in hexane (1.72 ml). After being stirred at -10° for 15 mins, the solution is cooled to -78° and treated dropwise over 9 mins with a solution of benzyl acetate (0.620 g, 4.13 mmol) in anhydrous THF (3.5 ml). After stirring 15 more mins at -78° C. the reaction mixture is treated dropwise over 13 mins with a solution of N-(t-butyldimethylsilyl)-4-(2-oxoethyl)-azetidin-2-one (0.894 g, 3.93 mmol) in anhydrous THF (6 ml). The reaction mixture is stirred at -78° an additional 15 mins and then quenched with 2.5N HCl (6 ml). EtOAc (100 ml) is added and the oragnic phase is separated, washed with H2O (2×20 ml), 5% NaHCO3 (20 ml) and brine, dried with MgSO4, and filtered. The filtrate is evaporated i.v. and the residue stripped with φH to yield N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-hydroxypropyl)-azetidin-2-one (1.432 g) as an oil: ir (neat) 2.87, 5.73, 5.79, 7.57, 7.96, 8.39, 11.92, and 12.16 cm-1 ; mass spectrum m/e 362, 320, 278, 170 and 128.

Provenance & Evidence