Montmorillonite Clay Catalysis. Part 7.1 An Environmentally Friendly Procedure for the Synthesis of Coumarins via Pechmann Condensation of Phenols with Ethyl Acetoacetate†

Abstract

Coumarins are synthesised via Pechmann condensation of phenols with ethyl acetoacetate catalysed by montmorillonite clay in satisfactory yields; the scope and limitation of the method have been investigated.

Integrated Catalytic Process to Directly Convert Furfural to Levulinate Ester with High Selectivity

“…Reaction conditions: to a 100 mL autoclave with Teflon liner were added furfural (1.5 mL), Pt supported on ZrNb binary phosphate (Zr/Nb, 1:1; treated at 673 K in air; Pt loading: 2.0 wt %; 0.2 g), and absolute ethanol (8.5 mL). Solid acid catalysts have been extensively explored based on various solid materials such as zeolites, [16] nafion-H, [17] amberlyst, [18] montmorillonite K 10, [19] poly(anilinesulfate) salt, [20] heteropoly acids, [21] functionalized mesoporous silica, [22] and metal oxides or modified metal oxides. Results of screening experiments over various alcohol solvents.…”

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

“…Ionic liquids [17] and microwave irradiation [18] have been applied to the Pechmann reaction, but these methods also generated strongly acidic wastes and they utilize highly expensive and non-recyclable reagents. To improve the above mentioned problems, a number of heterogeneous alternatives such as Amberlyst ion-exchange resins [19], zeolites [20,21], montmorillonite K-10 [22], polyaniline sulfate salt [23,24], heteropoly acids [25], nafion resin/silica nanocomposites [26], nano-crystalline sulfated-zirconia [27] and sulfonic acid functionalized SBA-15 silica [28] have been employed for this purpose in Pentafluorophenylammonium triflate Coumarins Pechmann reaction Phenols…”

A Solvent-Free Synthesis of Coumarins Using Phosphotungstic Acid as Catalyst

“…Among these, the Pechmann reaction is the most widely used method, as the reaction involves the use of simple starting materials, that is, phenols and b-ketoesters, in the presence of acidic condensing agents. The use of various reagents such as H 2 SO 4 , P 2 O 5 , FeCl 3 , ZnCl 2 , POCl 3 , AlCl 3 , PPA, HCl, phosphoric acid, trifluoroacetic acid, montmorillonite and other clays are all well documented in the literature [26]. Most of these methods suffer from severe drawbacks including the use of a large amount of catalysts, sometimes long reaction times and very often temperatures to the extent of 150°C.…”