Triethylamine → Ethyl 3-methyl-2,4,5,6-tetrahydrocyclopenta[c]pyrrole-1-carboxylate

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A procedure for the synthesis of pyrroles via N-(3-oxo-1-alkenyl)glycine ester was adapted from Hombrecher and Horter, Synthesis 389, 1990. Ethyl aminoacetate hydrochloride (28 g, 0.20 mol) and triethylamine (20.1 g, 0.20 mol) were added to a solution of 2-acetylcyclopentanone (25.0 g, 0.20mol) in ethanol (400 ml). The solution was stirred at room temperature for 15 hours and concentrated. The residue was combined with water (250 ml), and extracted with methylene chloride (4×100 ml). The combined extract was washed with water (100 ml), dried (sodium sulfate), and concentrated to leave a light brown oil. The oil was added with stirring at 50° C. to a solution of sodium ethoxide (14 g, 0.20 mol) in absolute ethanol (400 ml). The mixture was heated at 80° C. for 3 hours and poured into water (500 ml) to precipitate a light yellow solid. Recrystallization from ethanol gave ethyl 3-methyl-2,4,5,6-tetrahydrocyclopenta[c]pyrrolecarboxylate 4j, 9.1 g (24%)as a pale yellow solid, mp 166°-167° C.; 1H NMR (CDCl3): δ 8.38 (s, 1H), 4.24 (q, 2H), 2.78 (t, 2H), 2.52 (t, 2H), 2.30 (m, 2H), 2.18 (s, 3H), 1.30 (t, 3H). Anal. calcd for C11H15NO2 : C, 68.39; H, 7.77; N, 7.25. Found, C, 68.40; H, 7.85; N, 7.15.

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