Three-Component Synthesis of Substituted Chromenes

Significance

Reported is the synthesis of 2-amino-3-cyano-4-allyl chromenes through the room-temperature three-component reaction of salicyl­aldehydes, malononitrile, and allyl bromides in the presence of sodium iodide and indium metal in water. A multi-stage mechanism is proposed, as shown, in which the malononitrile and aldehyde first undergo a Knoevenagel condensation, with subsequent phenolic OH attack to give the chromene. The resulting species undergoes reaction with an allylindium species to give the product. The reaction does not proceed well in organic solvents, or in the absence of sodium iodide.