Thioacetals are the sulfur analogue of acetals. They are prepared in a similar way to acetals: by reacting a thiol with an aldehyde:
Dithioacetals are prepared similarly to thioacetals, which are intermediates:
Such reactions typically employ either a Lewis or Brønsted acid catalyst.
Dithioacetals generated from aldehydes and 1,2-ethanedithiol are useful in organic synthesis:
Whereas the carbonyl carbon of an aldehyde is electrophilic, the deprotonated derivatives of dithioacetals feature nucleophilic carbon centers:
Again, this reactivity is most commonly exploited in the 1,3-dithiolanes. The inversion of polarity between R'(H)Cδ+Oδ- and R'CLi(SR)2 is referred to as umpolung.