Flavonoids, 39. The reaction of 3-mesyloxyflavanones with O- and S-nucleophiles,synthesis of 3-thiocyanato- and 3-acetylthio-flavanones

The action of either cyanate or acetate ions on $\text{trans}$-3-mesyloxyflavanones $\text{1}$ led to the formation of flavones $\text{2}$ and aurones while the reaction with the respective S-nucleophiles (thiocyanate and thioacetate ions) resulted in $\text{cis}$-and $\text{trans}$-3-thiocyanato- and 3-acetylthioflavanones ($\text{6}$ and $\text{11}$). The participation of the concurrent nucleophilic substitution, β-elimination and elimination with ring-contraction is dependent on the “hard-soft” character of the nucleophile and the increase of the “soft” character favours the displacement.