Introduction of Agar-Entrapping as a Novel Strategy to Improve the Catalytic Activity of Moisture-Absorbing Acidic Ionic Liquids: A Case Study in the Synthesis of 5-Arylidene Barbituric Acids and Pyrano[2,3-d]Pyrimidinones

Importance of Hybrid Catalysts toward the Synthesis of 5H-Pyrano[2,3-d]pyrimidine-2-ones/2,4-diones (Thiones)

“…Table 8 shows diverse reaction conditions by utilizing ILs to synthesize pyrano [2,3-d] 207 did a case study of the synthesis of pyrano [2,3-d]pyrimidine derivatives. From the table, entries 11 and 12 showed that by using these reaction conditions, higher isolated yield of the product were obtained in shorter reaction time.…”

“…Here various ionic liquids such as [SuSA-H]­HSO 4 , [H-Suc]­HSO 4 , [H 2 -DABCO] 9 [H 2 PO 4 ] 2 , [H 2 -Bisim]­[HSO 4 ] 2 or [H 2 -Bisim]­[ClO 4 ] 2 , [C 4 (Mim) 2 ]·2Cl or [C 4 (Mim) 2 ]·2HSO 4 , [(DABCO) 2 C 3 H 5 OH]·2Cl, [C 4 (DABCO) 2 ]·2­(OH), agar-entrapped [DABCO]­(SO 3 H) 2 (Cl) 2 , [H 2 -BiPy]­[ClO 4 ] 2 , [TPPHSP]­Br, [ l -proline]­NO 3 , bead-PIL, and IL-MIL-101­(Fe) were reported for the synthesis of 162 . Shirini et al did a case study of the synthesis of pyrano­[2,3- d ]­pyrimidine derivatives. From the table, entries 11 and 12 showed that by using these reaction conditions, higher isolated yield of the product were obtained in shorter reaction time.…”

Recent advancements in the multicomponent synthesis of heterocycles integrated with a pyrano[2,3-d]pyrimidine core

“…This method involves the tolerable facile synthesis of the catalyst and is suitable for enhanced yields. 64 …”

“…Yelwande et al 63 have reported the synthesis of bicyclic pyranopyrimidines with enaminonitrile moieties (8 examples, 90-95% yields) under catalytic conditions of SnO 2 /SiO 2 (15 wt%) nanocomposite, succeeding in a green protocol in ethanol at room temperature. Furthermore, Moghaddampour et al 64 have reported the preparation and utility of agar-trapped acidic ionic liquid (0.05 g) as a recyclable catalyst for the synthesis of bicyclic pyranopyrimidines 12a-h with improved yields compared to the previous methods for the preparation of this series of compounds. 65,66 Consequently, aryl aldehydes reacted with (thio)barbituric acids and malononitrile in water at reux temperature provided the bicyclic pyranopyrimidines 12a-h in a green technique, and remarkable yields (Scheme 7).…”

“…This method involves the tolerable facile synthesis of the catalyst and is suitable for enhanced yields. 64 In another route, a choline chloride-based DES "ChCl/urea/ thiourea" supported the multicomponent synthesis of 1,3,4,5tetrahydro-2H-pyranopyrimidines 13 that were previously prepared using other catalytic conditions e.g. Fe 3 O 4 @MCM-41@Zr-piperazine, Fe 3 O 4 @Ph-PMO-NaHSO 4 nanocatalysts, and DABCO-based ionic liquid {[H 2 -DABCO] [H 2 PO 4 ] 2 }.…”