Access to a Key Intermediate for the Synthesis of 1-thia-analogue of Quercetin

We described here the access to 2-mercapto-4,6-dimethoxy-benzoic acid a key intermediate in the synthesis of the thia-analogue of quercetin. Two syntheses were attempted. The first one using a previously described strategy afforded only very modest yields of the requested compound. The second one which is original is based on the transposition by thermolysis of the appropriately functionalized phenol O-thiocarbamate precursor into the corresponding thiophenol S-thiocarbamate gave fair results which are currently under optimisation.