Heterocyclic Compounds. Part XXXVII. Synthesis of Scopoletin

Scopoletin or 7-hydroxy-6-methoxycoumarin has been synthesised by three different routes : (a) By oxidising 7-mesyloxy- or 7-tosyloxy-coumarin with alkaline potassium persulphate to 7 -mesyloxy- or 7-tosyloxy-6-hydroxycouniarin, which on methylation and subsequent removal of the mesyl or tosyl group provides scopoletin. (b) Preferential tosylation of 6,7-dihydroxycoumarin to 7-tosyloxy-6-hydroxycoumarin, methylation of the latter, and subsequent removal of the tosyl group also provide scopoletin. (c) Oxidation of the 6,7-dimethoxycoumarin by alkaline potassium persulphate takes an abnormal course, resulting in the formation of scopoletin