Carbon Dioxide → HCID 68919869, compound

Participants

Reaction Steps

A mixture of indoline 2-carboxylic acid (10.60 g, 65 mmol) and dimethyl acetylenedicarboxylate (9.24 g, 80 mmol) in acetic anhydride (110 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. where carbon dioxide evolution was most intense. The temperature was maintained until gas evolution had ceased (ca. 10 h). The dark solution was concentrated in vacuo and the solid residue was crystallized from methanol to yield 3-methyl-8H-3a-aza-cyclopenta[a]indene-1,2-dicarboxylic acid dimethyl ester, 14.40 g (78%): mp 162-164° C.; 1H NMR (DMSO-d6) δ 2.74 (3H, s, Me), 3.85 and 3.89 (each 3H, s, 2×OMe), 4.01 (2H, s, CH2) 7.20-7.27 (1H, m, ArH), 7.33-7.37 (1H, m, ArH), 7.46-7.53 (2H, m, 2×ArH). Anal. Calcd. for C16H15NO4: C, 67.36; H, 5.30; N, 4.91. Found: C, 67.30; H, 5.31; N, 4.85.

Provenance & Evidence