Pechmann coumarin synthesis

Lewis and Brnnsted acid-mediated condensation of phenol with p-ketoester to produce coumarin. Some call it the von Pechmann cyclization. 

Name Reactions A Collection of Detailed Mechanisms and Synthetic Applications, DOI 10.1007/978-3-319-03979-4 208, Springer International Publishing Switzerland 2014 

von Pechmann, H. Duisberg, C. Ber. 1883, 16, 2119. Hans von Pechmann (1850-1902) was bom in NOmberg, Germany. After his doctorate, he worked with Frankland and von Baeyer. Pechmarm taught at Munich and Tubingen. He committed suicide at 52 by taking cyanide. 

Shockravi, A. Heravi, M. M. Valizadeh, H. Phosphorus, Sulfur Silicon Relat. Elem. 2003,178,143. 

Lewis acid-mediated condensation of phenol with P-ketoester to produce cou- 

Name Reactions 4th ed., DOI 10.1007/97S-3-642-01053-8 195, Springer-Verlag Berlin Heidelberg 2009 

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The most important FBAs in the coumarin series are the 7-amino-3-phenylcoumarins which are prepared via the Pechmann coumarin synthesis. For example, m-aminophenol may be condensed with ethyl 3-hydroxy-2-phenylacrylate in the presence of a Lewis acid in nitrobenzene (Scheme 13). 

An acidic resin can be used in place of sulfuric acid for the von Pechmann" " coumarin synthesis. For condensalions such as Ihal of resorcinol with ethyl ticeto-acetate, the two resins indicated appear to he equally salisl actory (/eu-Karb is a British polystyrenesulfonic acid). Use of a resin slmplllled puriflcalion of the eroduot. 

Pechmann Coumarin Synthesis Brian A. Lanman 8.5.1 Description... 

The Pechmann coumarin synthesis, also known as the Pechmann condensation or Pechmann reaction, is the Lewis or Bronsted acid-promoted condensation of phenols (1) and P-keto (or other 3-oxo aliphatic) esters (2) to produce coiunarins (2//-chromen-2-ones, 3). ... 

Owing to exceptional sensitivity of the tricyclic phenol (A) to acidic reagents, direct condensation with 2-carbethoxycyclopentane-l,3-dione (i) under von Pechmann coumarin synthesis conditions proved impossible. However, the bromide (ii) readily underwent condensation to give the desired coumarin ring D when zinc carbonate was used both as catalyst and acid scavenger. 

A remarkable ring closure of polyenic acetals can be performed in a highly stereospecific manner with SnCl4 to form polycyclic products with a multiplicity of asym. centers. 3-Alkyl-4-halogeno-tetrahydropyrans can be obtained by a novel reaction of olefins with paraformaldehyde and hydrogen halides . 1,3-Diphenyl-naphtho[2,3-c]furan, the first known stable 2,3-naphthoquinonoid, is an extremely reactive diene component in Diels-Alder syntheses . A modified Pechmann coumarin synthesis uses enamine derivatives of yS-ketoacids without catalyst. ... 

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