benzyl pyrazolidine-1-carboxylate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of sodium hydroxide (93.0 mL of 1N solution, 93.0 mmol) is added CH2Cl2 (280 mL) followed by pyrazolidine-1-carboxylic acid benzyl ester (15.0 g, 61.8 mmol) and then ethyl-3-chloro-3-oxopropionate (11.1 mL, 86.5 mmol). After stirring the biphasic mixture vigorously for 3 hours at room temperature, the mixture is quenched by pouring into aqueous saturated NH4Cl. The organic phase is dried (MgSO4), filtered and concentrated in vacuo. The crude residue is purified over silica (10% EtOAc/hexanes) to afford 15.5 g (78% yield) of the desired product. 1H NMR (300 MHz, CDCl3) δ 7.38 (s, 5H), 5.23 (dd, J=11.8, 8.4 Hz, 2H), 4.19-4.07 (m, 4H), 3.65 (d, J=15.9 Hz, 1H), 3.31 (d, J=15.9 Hz, 1H), 3.20-3.15 (m, 2H), 2.20-2.04 (m, 2H), 1.26 (t, J=7.2 Hz, 3H); ESI+ MS: m/z (rel intensity) 321.0 (100, M++H). the mixture is quenched by pouring into aqueous saturated NH4Cl The organic phase is dried (MgSO4) filtered concentrated in vacuo The crude residue is purified over silica (10% EtOAc/hexanes)