Yield:5336-48-1 64%

Reaction Conditions:

with sodium ethanolate in diethyl ether; for 0.5 h;Reflux;Inert atmosphere;

Steps:

Ethyl 1-(tert-Butyl)-4,5-dioxopyrrolidine-3-carboxylate (17).

To a solution of freshly prepared solid NaOEt (19.6 g, 288 mmol) in anhydrous ether (125 mL) under N2 was added diethyl oxalate (42.2 g, 288 mmol) followed by dropwise addition of amino ester 16 (45.8 g, 288 mmol) in dry ether (125 mL) over a period of 5 min. The resulting solution was heated at reflux for 30 min and then let stand overnight. The solvent was removed and the resulting pale yellow solid was dissolved in H2O (1500 mL) and then acidified slightly with 20% aqueous HCl. The mixture was placed in a separatory funnel and the organic layer separated. The aqueous layer was allowed to stand for 24 h, which yielded 31.9 g of 17 as white crystals. The organic layer was evaporated under reduced pressure to yield an additional 7.3 g of 17, for a combined 39.2 g (64%) of 17. Recrystallization from petroleum ether (60-120 °C) gave mp 120-122 °C (lit.9 mp 126.5-127.5 °C). (Enolic form) 1H NMR 4.33 (q, 2H, J 7.0 Hz), 4.04 (s, 2H), 3.85 (s, 1H), 1.49 (s, 9H), 1.34 (t, 3H, J 7.0 Hz).

References:

Saulnier, Mark G.;Schreiber, Steven M.;Cavanaugh, Kerri L.;Perni, Robert B.;Joyner, H. Howard;Gribble, Gordon W. [Arkivoc,2020,vol. 2021,# 5,p. 15 - 23]