2-Substituted 1,3-Benzoxathiolium Tetrafluoroborates as Useful Acylating Agents of Electron-Rich and Heteroaromatic Compounds

2-Substituted 1,3-benzoxathiolium tetrafluoroborates were used for the two-step acylation of electron-rich aromatic and heteroaromatic compounds: 1,3-dimethoxybenzene, 1,3,5-trimethoxybenzene, pyrrole and indoles. In most of the cases intermediate 2,2-disubstituted 1,3-benzoxathioles were obtained in good to high yields (55-100%) and subsequent hydrolysis of these with mercury(II) oxide and aqueous tetrafluoroboric acid (35%) in tetrahydrofuran afforded the corresponding ketones in almost quantitative yields.