Eschenmoser coupling

What is Eschenmoser coupling?

Fischli and Eschenmoser first reported this chemical reaction in 1967 during the synthesis of vitamin B12, which involves the alkylation of secondary or tertiary thioamides with an electrophilic reagent followed by the extrusion of sulfur, resulting in the formation of vinylogous amides and urethanes.

Eschenmoser coupling - general reaction scheme - Eschenmoser coupling reaction - Eschenmoser's method - Eschenmoser sulfide contraction - Eschenmoser sulfide contraction methodology - Eschenmoser sulfide reaction
Eschenmoser coupling

X = halogen

It is commonly known as the Eschenmoser coupling, Eschenmoser coupling reaction, Eschenmoser’s method, Eschenmoser sulfide contraction, Eschenmoser sulfide contraction methodology, or Eschenmoser sulfide reaction. Although this reaction is similar to the aza Claisen-Schmidt condensation, it is not ideal for introducing meso substituents.


Fischli, A. and Eschenmoser, A. (1967), A Synthetic Route to Metal-free Corrins. Angew. Chem. Int. Ed. Engl., 6: 866-868.