... One-Pot Synthesis of Coumarins 5; General Procedure. ... The residue was dissolved in 10% K 2 CO 3 in MeOH-acetone (∼1:1, 10 mL) at 0 °C, and stirred for another 2 h. The solvent was evaporated to dryness, the residue was dissolved in H 2 O (15 mL) and ... Bauerle P. Angew. ...