Reactions of silica chloride (SiO2Cl)/DMSO, a heterogeneous system for the facile regeneration of carbonyl compounds from thioacetals and ring-expansion annelation of cyclic thioacetals

Silica chloride (SiO2Cl)/DMSO, as a heterogeneous system, has been efficiently used for deprotection of thioacetals into aldehydes in dry CH2Cl2 at room temperature. Thioketals without enolizable hydrogens adjacent to a sulfur atom are converted easily to the corresponding ketones in high yields under similar reaction conditions. However, thioketals with enolizable methyl and methylene groups undergo ring-expansion reactions to afford 1,4-dithiepins and 1,4-dithiins in dry CH2Cl2 at room temperature in good yields.