Fe₃O₄@SiO₂@D‐NHCS‐Tr as an efficient and reusable catalyst for the synthesis of indol‐3‐yl‐4H‐chromene via a multi‐component reaction under solvent‐free conditions

Abstract

Fe 3 O 4 @SiO 2 @D-NHCS-Tr was used as an efficient catalyst in the threecomponent reaction between indole derivatives, salicylaldehyde, and active methylene compounds under solvent-free conditions to the synthesis of indol-3-yl-4H-chromene derivatives. The features of this method include the green conditions of the reaction, easy separation, eco-friendly and cost-effectiveness of the catalyst, and high yield in short reaction times.

Recent Advances of Three‐component Reactions of Simple Indoles

“…On the other hand, isocyanate 17.3 [24] and carbonyl 17.4 [25a–f] could also act as acceptors. The use of novel catalysts, such as Fe 3 O 4 @SiO 2 @D‐NHCS‐Tr, [25b] heterogeneous amberlite IRA‐400 Cl, [25d] TH catalyst (an acid hydrolysate of tendons), [25e] have been reported recently.…”

“…On the other hand, isocyanate 17.3 [24] and carbonyl 17.4 [25a–f] could also act as acceptors. The use of novel catalysts, such as Fe 3 O 4 @SiO 2 @D‐NHCS‐Tr, [25b] heterogeneous amberlite IRA‐400 Cl, [25d] TH catalyst (an acid hydrolysate of tendons), [25e] have been reported recently. Bhusare [25f] utilized L ‐proline as an organic catalyst (10 mol%) in metal‐free reactions of indoles, salicylaldehydes and 4‐hydroxy coumarins (Scheme 17).…”