Carbon Dioxide → HCID 68914665, compound

Participants

Reaction Conditions

Reaction Steps

A mixture of 1-propionyl-2,3-dihydro-1H-indole-2-carboxylic acid (4.49 g, 20.5 mmol) and dimethyl acetylenedicarboxylate (5.68 g, 40 mmol) in acetic anhydride (40 mL) was stirred in a flask equipped with a reflux condenser and a gas bubbler to monitor carbon dioxide evolution during the reaction. The mixture was heated to 120° C. for 4 hours until no gas was eliminated. The dark solution was concentrated in vacuo to dryness and the solid residue was recrystallized from methanol to yield 3-ethyl-8H-3a-aza-cyclopenta[a]indene-1,2-dicarboxylic acid dimethyl ester, 4.61 g (75%): mp 86-88° C.; 1H NMR (DMSO-d6) δ 1.22 (3H, t, J=7.4 Hz, Me), 3.08 (2H, q, J=7.4 Hz, CH2), 3.75 and 3.76 (each 3H, s, 2×OMe), 4.07 (2H, s, CH2), 7.27-7.31 (1H, m, ArH), 7.43-7.47 (1H, m, ArH), 7.59-7.64 (2H, m, ArH). Anal. Calcd. for C17H17NO4: C, 68.21; H, 5.72; N, 4.68. Found: C, 68.22; H, 5.74; N, 4.65.

Provenance & Evidence