Einhorn acylation

What is Einhorn acylation?

Einhorn and Hollandt first reported the acylation of alcohols using anhydride or acyl halide in a tertiary amine such as pyridine, now known as the Einhorn acylation, Einhorn reaction, and Deninger-Einhorn method, where tertiary amines function as both nucleophilic acylation catalysts and acid scavengers.

Einhorn acylation - general reaction scheme - Einhorn reaction - Deninger-Einhorn method
Einhorn acylation
  • R1 = H, alkyl, aryl
  • R2 = alkyl, aryl
  • R = alkyl, aryl
  • X = halogen, OC(O)R

The use of highly nucleophilic tertiary amines, including triethylamine, DMAP, DABCO, and PMP, have been employed for this reaction, and chiral tertiary amines as catalysts can selectively acylate secondary alcohols to yield chiral esters.

The preparation of esters from alcohols and acylation reagents such as acyl halides and anhydrides finds extensive application in this reaction.

References

Einhorn, A., Hollandt, F. and Von Alfred Einhorn, M. (1898), Ueber die Acylirung der Alkohole und Phenole in Pyridinlösung. [On the Acylation of Alcohols and Phenols in Pyridine Solution.] Justus Liebigs Ann. Chem., 301: 95-115. https://doi.org/10.1002/jlac.18983010111

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