Geometrical inversion in the acids derived from the coumarins Part II. Cis to trans

A rapid and efficient method has been found for preparing coumaric acid and 4-methylcoumaric acid from coumarin and 7-methylcoumarin respectively by treatment with mercuric oxide in the presence of cold alkali. 5-nitrocoumaric acid is not produced in the cold and is formed only by boiling the mixture of 6 nitrocoumarin, mercuric oxide and alkali. The action of cold alkali and mercuric acetate or of hot alkali and mercuric oxide on coumarin yields mercurated coumaric acids. From these pure coumaric acid can be produced by using ammonia and hydrogen sulphide