One-pot synthesis of coumarins

The synthesis of coumarins (2H-benzopyran-2-ones) via Knoevenagel condensation over a recoverable, inexpensive solid base catalyst, calcined Mg–Al hydrotalcite, is reported for the first time. This method produces substituted coumarins in very high yields (>85%) and selectivities (ca. 100%) when aromatic hydroxy aldehydes are reacted with 2-substituted ethyl acetate.