Thioacetal and thioketal formation:

Thioacetals and thioketals are the sulfur equivalents of acetals and ketals and are as well prepared within acid conditions. These can as well be employed to protectaldehydes and ketones, although the hydrolysis of these groups is much more difficult. More significantly, the thioacetals and thioketals can be removed through reduction and this gives a method of reducing aldehydes and ketones.

Figure: Formation of (a) cyclic thioacetals and (b) cyclic thioketals.