In a 50 mL two-necked round-bottomed flask fitted with a magnetic stirrer, fitted with a reflux condenser and connected to a calcium chloride drying tube, isophthalic acid (1 g, 8.1 mmol) was suspended in boron trifluoride ethyl ether complex (10 mL). The reaction mixture was stirred and heated at 120 °C overnight, during which the milky white mixture gradually changed to a brown solution. The progress of the reaction was monitored by thin-layer chromatography (unfolding agent: hexane/ethyl acetate, 3:1, v/v) to confirm that the reaction was complete. After the reaction mixture was cooled, it was diluted with deionized water (25 mL) and subsequently extracted with ethyl acetate (3 x 10 mL). The organic phases were combined and washed with saturated sodium bicarbonate solution until no bubbles were produced. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to give 1.11 g of crude product in 92% yield.
