Phosphoric Acid → 1-Benzyl-5-oxo-pyrrolidine-3-carboxylic acid

Participants

Reaction Steps

A mixture of isopropyl N-benzylpyrrolidin-2-one4-carboxylate (Example 33, 3.93 g) in dioxane (80 mL), aqueous KOH (2 N, 40 mL) and MeOH (60 mL) was stirred at room temperature for 1 hour. The mixture was then cooled with ice, acidified to pH=4 with H3PO4 and left in a refrigerator overnight. The precipitate was filtered and the filtrate was concentrated to give a yellow oil. The oil was contaminated with dioxane, and therefore was dissolved in aqueous KOH. The solution was extracted with CHCl3 (2×20 mL), and the aqueous layer was acidified with HCl (3 N). It was extracted with CHCl3 (4×30 mL). The combined extracts were dried (Na2SO4) and concentrated in vacuo to give N-benzylpyrrolidin-2-one-4carboxylic acid as a pale yellow oil (2.89 g): 1H NMR (300 MHz) δ 10.77 (br s, CO2H), 7.34 (m, 5 H), 5.17 (d, J=14.9 Hz, 1 H), 4.02 (dd, J=9.4, 3.2Hz, 1 H), 3.98 (d, J=14.1 Hz, 1 H), 2.12-2.71 (m, 4 H); 13C NMR (75 MHz) δ 176.47, 174.32, 135.25, 128.78, 128.46, 127.90, 58.63, 45.69, 29.57, 22.83; MS (FAB), m/e 220 (100, M+H), 174 (40); HRMS (FAB) m/e calcd for (C12H13NO3+H) 220.0974, found 220.0984.

Provenance & Evidence