Silica Sulfuric Acid–Mediated Synthesis ofβ-Enaminones andβ-Enaminoesters Under Microwave Irradiation

Abstract

GRAPHICAL ABSTRACTOAbstract Silica sulfuric acid, a heterogeneous reagent, has been found to be an efficient catalyst for the synthesis of β-enaminones and β-enaminoesters under microwave irradiation in a microwave reactor within 2 min. The experimental procedure is simple and environmentfriendly, and results in excellent yields of the products. Further, the catalyst is recyclable, and the reaction is 60 times faster than the reaction at room temperature.

The One-Step Synthesis of 3,4-Dihydropyrano[F]Chromene Derivatives in Under Grinding as an Environmentally Friendly Alternative

“…IR spectra were obtained on an ABB FT-IR (FTLA 2000) spectrometer. 1 HNMR and 13 C NMR spectra were recorded on a Bruker DRX-300 AVANCE at 300 and 75MHz (respectively) using TMS as internal standard and CDCl 3 as solvent. Mass spectra data were obtained using a GC-MS Hewlett Packard (EI, 20 e V) instrument.…”

“…1 As a result, a large number of methods have appeared describing novel synthesis of these heterocycles. 2-Amino-4H-benzochromenes have been of interest because of their biological activity 3 and a few methods have been reported for their synthesis.…”

Silica supported Fe(HSO4)3 as an efficient, heterogeneous and recyclable catalyst for synthesis of β-enaminones and β-enamino esters

“…Condensation reactions of carbonyl compounds with amines in the presence of various acid catalysts like Yb(OTf) 3 [10], Zn(O 4 Cl) 2 [11,12], InBr 3 [13], CoCl 2 [14], and LiHSO 4 ·SiO 2 [15] are well reported for the synthesis of ␤-enaminones and enamino esters. Additionally, non-conventional techniques such as microwave and ultrasound are also reported [16][17][18]. However, these methods are associated with certain drawbacks like use of moisture sensitive metal triflates and tedious workup [10], requirement of drastic conditions and use of harmful reagents [11], use of homogenous and non recyclable catalyst [12][13][14].…”

Facile, mild and selective silica sulfuric acid catalyzed oxidation of benzylalcohols to benzaldehyde derivatives by potassium peroxodisulfate

“…For this purpose, silica sulfuric acid (SSA), as a mild, inexpensive, efficient, reusable, environmentally safe and solid heterogeneous acid catalyst or promoter, could be used. SSA have frequently been used for many organic transformations because of its low cost, ease of preparation, catalyst recycling, ease of handling and easy separation from reactants and products [19][20][21][22][23][24]. SSA can enhance the reactivity and selectivity of many types of reaction, such as oxidation [25], carboncarbon bond formation for example aldol and Knovenagel condensation [26,27], Friedel-Crafts alkylation [28], Beckmann rearrangement [29], cycloaddition [30], aromatization [31] protection [32] and deprotection [33].…”