Eine neue Flavon‐Synthese

The Chemistry of Coumarins.

“…In view of the unexpected behavior of phloroglucinol, they extended the reaction to resorcinol. Simonis and Remmert (214) had studied this condensation and assigned to the condensation product obtained the constitution 7-hydroxy-2,3-dimethyl-l, 4benzopyrone (I). Robertson and coworkers found that Simonis' so-called chromone was identical with 7-hydroxy-3,4-dimethylcoumarin (II).…”

Facile iron(III) chloride hexahydrate catalyzed synthesis of coumarins

“…[15][16][17][18][19] The Pechmann reaction 20 is known as one of the most valuable methods for the synthesis of coumarins since it proceeds from simple starting materials, a phenol and a -keto ester, together with an acid catalyst. Various protocols have been developed by using different catalysts including sulfuric acid, 20 trifluoroacetic acid, 21 phosphorus pentaoxide, 22 aluminium chloride, [23][24] indium(III) chloride, 25 titanium(IV) chloride, 26 silica gel supported zirconyl chloride octahydrate, 27 samarium(III) nitrate hexahydrate, 28 bismuth(III) nitrate pentahydrate, 29 ionic liquids 30 and many more. [31][32][33] However, the development of practical, efficient and environmentally benign synthetic protocols for the synthesis of coumarins is greatly desirable.…”

Pentafluorophenylammonium triflate (PFPAT): An efficient, metal-free and reusable catalyst for the von Pechmann reaction

“…Classically, the process consists of the condensation of phenols with b-ketoesters in the presence of a variety of reagents to give good yields of 4-substituted coumarins [10]. Several acid catalysts have been used in the von Pechmann reaction including sulfuric acid [11], aluminium chloride [12], phosphorus pentoxide [13], trifluoroacetic acid [14] and other acids [15]. However, in many of these methods an excess amount of acid is needed to complete the reaction; for instance, reactions conducted in sulfuric acid [11] and trifluoroacetic acid [14] required 10-12 and 3-4 equivalent amount of acid respectively.…”