Thioacetal

    Thioacetals are the sulfur analogue of acetals. They are prepared in a similar way to acetals: by reacting a thiol with an aldehyde:

RSH + R'CHO → R'CH(OH)SR

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Dithioacetals are prepared similarly to thioacetals, which are intermediates:

RSH + R'CH(OH)SR → R'CH(SR)₂ + H₂O

Such reactions typically employ either a Lewis or Brønsted acid catalyst.

Dithioacetals generated from aldehydes and 1,2-ethanedithiol are useful in organic synthesis:

C₂H₄(SH)₂ + R'CHO → R'CHS₂C₂H₄ + H₂O

Whereas the carbonyl carbon of an aldehyde is electrophilic, the deprotonated derivatives of dithioacetals feature nucleophilic carbon centers:

R'CHS₂C₂H₄ + R₂NLi → R'CLiS₂C₂H₄ + R₂NH

Again, this reactivity is most commonly exploited in the 1,3-dithiolanes. The inversion of polarity between R'(H)C^δ+O^δ- and R'CLi(SR)₂ is referred to as umpolung.

See also

• Thioketal