Glycerin and CeCl3·7H2O: a new and efficient recyclable medium for the synthesis of bis(indolyl)methanes

Glycerol as Suitable Solvent for the Synthesis of Metallic Species and Catalysis

“…Lanthanide metals, in particular Ce III salts, have proven their ability as Lewis acid catalysts in glycerol for the synthesis of N‐containing heterocycles, such as bis(indoles),40 dihydropyridines,41 and quinoxalines,42 which exhibit a large range of biological activities.…”

A new approach for the synthesis of bisindoles through AgOTf as catalyst

“…Among the variety of Lewis acids employed in this reaction such as In(OTf) 3 (5 mol %)/[omim][PF 6 − ] [27], LiClO 4 (10 equiv) [28], Cp 2 ZrCl 2 (5 mol %) [29], Yb-amberlyst (16 mol %) [30], SmI 2 (THF) 2 (10 mol %) [31], Sb 2 (SO 4 ) 3 (5 mol %) [32], Dy(OTf) 3 (5–10 mol %) [33], Ln(OTf) 3 (0.10 M) [34], FeCl 3 ·6H 2 O (5 mol %)/[omim][PF 6 − ] [35], V(HSO 4 ) 3 (10 mol %) [36], Bi(NO 3 ) 3 (2–5 mol %) [37], or CeCl 3 ·7H 2 O (10 M) [38], Ag is a good alternative since it is one of the most abundant, cheaper, readily available metals and also displays low toxicity. We disclose here a pioneering strategy for the synthesis of bisindolylmethane derivatives via Ag activation of aldehydes.…”

Mn/Al2O3 and Mn/ZrO2 as selective catalysts for the synthesis of bis(indolyl)methanes: The role of surface acidity and particle morphology

“…These compounds have been synthesized via an electrophillic substitution reaction between an indole and an aldehyde or a ketone in the presence of an acid catalyst. A diverse class of Lewis acid catalysts such as RuCl 3 [20], Al 2 O 3 (acidic) in dry media [21], Heteropoly acids [22], AgBF 4 [23], Gold(I) [24], CeCl 3 Á7H 2 O [25], KHSO 4 [26], phosphated zirconia [27], iodine [28] have been investigated for their catalytic activity. The reported protocols indicate that these catalysts are associated with one or more disadvantages such as high cost, low thermal stability, high toxicity, tedious method of separation of products and the use of environmentally harmful organic solvents.…”