Sulphated tin oxide (STO)-catalyzed synthesis of arylated vinyl ethers

The C3 or O-alkylation of 4-hydroxycoumarin (formation of new C-C and C-O bond) is undoubtedly one of the most important and challenging reactions in synthetic chemistry due to its pharmaceutical utility. In this communication, we report sulfated tin oxide (STO)-catalyzed synthesis of arylated vinyl ethers in moderate to good isolated yields (68-93%) from the reaction of substituted phenyl acetylenes (terminal alkynes) with 4-hydroxy coumarin in polyethylene glycol (PEG 400) as solvent at 110 oC. The catalyst can be recycled up to 5 times without losing the significant yield.