Reactivity of the double bond in coumarins and related α-β unsaturated carbonyl compounds Part II. Reaction of mercury salts on coumarins

Abstract

In methyl alcoholic solution coumarin reacts with mercuric acetate to form 3:6:8-triacetoxymercuri-4-methoxymelilotic anhydride. By the action of sodium hydroxide and hydrogen sulphide β-methoxymelilotic acid is obtained from it and by the action of bromine 3:6:8-tribromocoumarin. 7-methylcoumarin behaves similarly giving a trimercury compound. 6-nitrocoumarin forms 3:8-diacetoxymercuri-6-nitro-4-methoxymelilotic anhydride which, with alkali and hydrogen sulphide, gives 5-nitrocoumaric acid and with bromine 3:8-dibromo-6-nitrocoumarin. It is therefore established that mercuric acetate reacts with the double bond in these coumarins and further mercurates the benzene ring in positions 6 and 8 if they should be free. Mercuric chloride adds on to the double bond in coumarin and 7-methylcoumarin. The reactions of these addition products have been studied. 6-nitrocoumarin does not react with this reagent.