Reimer–Tiemann Reaction of Coumarins

Abstract Improved yields of aldehydes from the Reimer–Tiemann reaction of coumarin and two of its derivatives, namely 7-methylcoumarin and 3,4-benzocoumarin, are obtained by carrying the reaction in a two-step procedure. Using crown ether as phase transfer catalyst, a further improvement in the yield of products is achieved. Additionally, coumarin and 7-methylcoumarin are shown to give dialdehydes under this condition. Dialdehydes are reported for the first time from the Reimer–Tiemann reaction.