Scope of the reaction^a,b.

^aThe reactions were carried out as follows: 3-arylcoumarins (2, 1.0 mmol), Cu(OAc)₂ (20 mol%) and 1,10-phen (20 mol%) in DMSO/H₂O (v/v = 3 : 1) at 135 °C for 18 h under air atmosphere.

^bIsolated yields.