Phosphotungstic Acid Catalysed Synthesis of β-Enamino Compounds under Solvent-Free Conditions

Abstract

A convenient eco-friendly procedure has been developed for the synthesis of b-enaminones and b-enamino esters by reacting 1,3-dicarbonyl compounds with amines in the presence of catalytic amounts of phosphotungstic acid (H 3 PW 12 O 40 , 1 mol%). The reaction proceeds smoothly at room temperature under solvent-free conditions and gives the corresponding b-enamino compounds in high to excellent yields.

A novel and reusable magnetic nanocatalyst developed based on graphene oxide incorporated strontium nanoparticles for the facial synthesis of β‐enamino ketones under solvent‐free conditions

“…Therefore, the synthesis of β‐enamino ketones has received a great deal of attention. A variety of synthetic procedures for β‐enamino ketones have been developed using a different range of catalysts …”

Silica-supported LiHSO4 as a highly efficient, heterogeneous and reusable catalytic system for the solvent-free synthesis of β-enaminones and β-enamino esters

“…The direct condensation of amines with ȕ-dicarbonyl compounds has been used as a useful synthetic route toward ȕ-enaminones and ȕ-enamino esters [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Several catalysts have been applied to achieve this transformation, including NaAuClO 4 [8], Bi(TFA) 3 [9], Sc(OTf) 3 [10], Zn(ClO 4 ) 2 .6H 2 O/MgSO 4 [11], Yb(OTf) 3 [16], I 2 [17], silica chloride [18], LaCl 3 .7H 2 O [19], Bi(TFA) 3 /tetrabutylammonium bromide [20], heteropoly acids [21], ceric(IV) ammonium nitrate [22] and phoaphotungstic acid [23]. There are also some synthetic approaches to ȕ-enaminones including condensation of methyl ketones with dimethylformamide dimethylacetal [24], cyclization of amino acids [25], aminolysis of dithioacetals [26], reductive cleavage of isoxazoles [27] and substitution of the imidoylbenzotriazoles with trimethylsilyl (TMS) enol ethers [28].…”

Synthesis of 14-aryl-14H-dibenzo[a,j]xanthene Derivatives Catalysed by Expanded Graphite under Solvent-Free Condition

“…However, benign synthetic method to overcome these limitation is still an important challenge. In continuation of our interest on the application of cheap and eco-friendly materials as catalysts for development of useful synthetic methodology, [31][32] we now report a novel and high yielding method for the preparation of 14-aryl-14H-dibenzo[a,j]xanthene derivatives using expanded graphite as an eco-friendly catalyst under solventfree conditions (Scheme 1).…”