Tosylat

Tosylat, or tosylate, is a chemical term used to describe either the p-toluenesulfonate anion or esters derived from p-toluenesulfonic acid. The tosylate group is commonly represented as -OTs. In salts, the anion is p-toluenesulfonate, for example sodium tosylate (NaOTs). In esters, alkyl or aryl tosylates have the form R–OTs or Ar–OTs. The p-toluenesulfonic acid itself is a strong organic acid with a pKa around −2.8 in water.

Tosylates are notable as leaving groups in organic synthesis. The tosylate anion is stabilized by resonance with the sulfonyl group, making alkyl tosylates excellent substrates for nucleophilic substitution and elimination reactions. They are typically prepared by converting alcohols to tosylates using p-toluenesulfonyl chloride (TsCl) in the presence of a base such as pyridine or triethylamine, yielding alkyl tosylates that can then undergo SN2 or SN1 processes with various nucleophiles.

Beyond leaving-group chemistry, the p-toluenesulfonyl (tosyl) moiety is widely used as a protecting group for amines. N-tosyl derivatives are common in organic synthesis because they are relatively stable under many conditions but can be removed when desired with appropriate reagents, enabling controlled sequences of reactions.

Applications of tosylates span traditional organic synthesis, medicinal chemistry, and materials science, where they serve as convenient intermediates, leaving groups, or protecting groups. Safety considerations include the moisture sensitivity and corrosiveness of reagents like TsCl and the irritant nature of tosylate compounds.