Silica-Supported Antimony(III) Chloride as Highly Effective and Reusable Heterogeneous Catalyst for the Synthesis of Quinoxalines

Abstract

Lewis acid site on silica-supported antimony(III) chloride (SbCl 3 /SiO 2 ) acts as a highly efficient catalyst, even for low activity substrates, in the preparation of quinoxaline derivatives. The results of TG-DTA and BET indicated that dispersed SbCl 3 coordinates with surface hydroxyl groups leading to formation-O-Sb-Cl as stable Lewis acid sites under the reaction condition. This user-friendly catalyst was found to be reusable without any loss of activity. The fact that SbCl 3 did not leach makes SbCl 3 /SiO 2 as alternative heterogeneous acid catalyst to the conventional homogeneous acids at room temperature. The wide range of turnover frequency values (11-800 h -1 ) shows that reaction rate is highly dependent on the nature of the functional groups on the aromatic ring of substrates.

Heterogeneous SnCl2/SiO2versus Homogeneous SnCl2Acid Catalysis in the Benzo[N,N]-heterocyclic Condensation

“…Initially, we examined the condensation of benzil with the less-reactive 4-nitrobenzene-1,2-diamine 37 to evaluate the efficiency of various metal salts as catalyst ( Table 2). The reaction was screened in MeOH 42 within 1 h using a catalytic amount of common Lewis acids (5 mol %) at room temperature (Scheme 1).…”

“…[36][37][38][39][43][44] The regioselectivity for 4-substituted 1,2-diaminobenzenes on treatment with phenylglyoxal in the presence of SnCl 2 /SiO 2 was also investigated (Table 5, entries [17][18][19][20]. With the exception of 2,3-diaminopyridine, which showed very high selectivity to cis-regioisomer 1t, [45][46] the condensation of other 4-substituted 1,2-diaminobenzenes with phenylglyoxal resulted in a mixture of regioisomers 1q-1s, in favor of trans-regioisomers [47][48][49] ( Fig.…”

“…Therefore, development of an efficient and environmentally benign method is still required. As part of our continuous efforts to develop eco-friendly catalytic processes, [36][37][38][39][40][41] herein, we introduce SnCl 2 /SiO 2 as a novel heterogeneous catalyst for the acid-catalyzed reactions, e.g. benzo[N,N]-heterocyclic condensation.…”

Indion 190 resin: Reusable catalyst for the synthesis of quinoxalines and pyrido-pyrazines at ambient temperature

“…Commonly employed method involves condensation of an aryl-1,2-diamine with a 1,2-dicarbonyl in refluxing ethanol or acetic acid for 2-12 h yielding 34-85% of product [10]. Several improved methods reported in the literature for the synthesis of quinoxalines include microwave synthesis [11], the use of PEG-400 [12], RuCl-(PPh3)3-TEMPO [13], CAN [14], CuSO4.5H2O [15], SA/MeOH [16], montmorillonite K-10 [17], InCl3 [18], Zn/proline [19], Ga(OTf)3 [20], HClO4-SiO2 [21], -cyclodextrins in water [22], FeMAP [23], TiO2-P25 [24], ZnO-beta zeolite [25], silica-supported antimony(III) chloride [26] as catalysts.…”

Silica-supported antimony(III) chloride as a mild and reusable catalyst for the Paal–Knorr pyrrole synthesis

“…Among the large number of Lewis acids used in organic synthesis, antimony trichloride has not been explored much for its catalytic activity (Maiti and Kundu 2006;Wu et al 2006;Singh and Peddinti 2007;Cepanec et al 2007;Zhang and Liu 2008;Liu et al 2008;Zhang and Yang 2009;Darabi et al 2009), while this compound is not only commercially available and inexpensive, but is also easier to handle than other metal halides such as InCl 3 , GdCl 3 , and TiCl 4 (Maiti and Kundu 2006). In contrast, reports on the safety of antimony trichloride show that its toxicity is high (LD 50 = 2.5 mg/100 g) (Stellman 1998).…”