Acetic Anhydride → Methyl indolizine-2-carboxylate

Participants

Reaction Steps

A 250-mL single-neck round-bottomed flask equipped with a magnetic stirrer and a reflux condenser was charged with acetic anhydride (80 mL) and 193a (6.68 g, 34.6 mmol). The reaction mixture was heated at reflux under nitrogen for 4 h. After this time the reaction was cooled to room temperature, poured onto the mixture of ice (100 g) and aqueous saturated sodium bicarbonate (200 mL), and stirred for 1 h. The resulting solution was neutralized with saturated aqueous sodium bicarbonate and extracted with methylene chloride (3×200 mL). The combined organic extract was dried over sodium sulfate and concentrated under reduced pressure. The residue was purified by silica-gel column chromatography eluting with 10:1 petroleum ether/ethyl acetate (10:1) to afford 193b as a white solid (2.1 g, 35%). MS-ESI: (M+H)+ 176.2. 1H NMR (500 MHz, CDCl3) δ 7.86-7.84 (m, 1H), 7.79 (d, J=1.0 Hz, 1H), 7.36-7.34 (m, 1H), 6.82 (s, 1H), 6.70-6.66 (m, 1H), 6.55-6.51 (m, 1H), 3.88 (s, 3H).

Provenance & Evidence