Pechmann condensation

Pechmann condensation
Named after Hans von Pechmann
Reaction type Ring forming reaction
Reaction
Phenol
+
β-keto carboxylic acid or β-keto ester
Coumarin(s)
Conditions
Temperature
Variable
Catalyst
Strong acids:
AlCl3, CH4SO3, H2SO4
Identifiers
Organic Chemistry Portal pechmann-condensation

The Pechmann condensation is a synthesis of coumarins, starting from a phenol and a carboxylic acid or ester containing a β-carbonyl group. The condensation is performed under acidic conditions. The mechanism involves an esterification/transesterification followed by attack of the activated carbonyl ortho to the oxygen to generate the new ring. The final step is a dehydration, as seen following an aldol condensation. It was discovered by the German chemist Hans von Pechmann .