Pechmann Condensation
Coumarin Synthesis

The Pechmann Condensation Allows The Synthesis Of Coumarins By Reaction Of Phenols With β-keto Esters.

Mechanism Of The Pechmann Condensation

The Reaction Is Conducted With A Strong Brønstedt Acid Such As Methanesulfonic Acid Or A Lewis Acid Such As AlCl₃. The Acid Catalyses Transesterification As Well As Keto-enol Tautomerisation:

A Michael Addition Leads To The Formation Of The Coumarin Skeleton. This Addition Is Followed By Rearomatisation:

Subsequent Acid-induced Elimination Of Water Gives The Product:

Recent Literature

Solvent-Free Coumarin Synthesis
T. Sugino, K. Tanaka, Chem. Lett., 2001, 110-111.

An Efficient And Practical Procedure For The Synthesis Of 4-Substituted Coumarins
S. K. De, R. A. Gibbs, Synthesis, 2005, 1231-1233.

Coumarin Syntheses Via Pechmann Condensation In Lewis Acidic Chloroaluminate Ionic Liquid
M. K. Potdar, S. S. Mohile, M. M. Salunkhe, Tetrahedron Lett., 2001, 42, 9285-9287.