Biomass‐derived Sugar Ionic Liquid as a Sustainable Organocatalyst: An Efficient Synthesis of Functionalized Dihydropyrano Coumarins

Abstract

Multi-component reaction approach was utilized in the synthesis of dihydropyrano coumarins under mild reaction conditions. Biomass derived carbohydrate was used as sugar source for the formation of D-ribose based sugar ionic liquid. The developed catalyst catalyzed efficient synthesis of these hetero atom functionalized compounds. A wide range of substrates were prepared with substituted aliphatic or aromatic aldehydes. Substitution in phenyl ring did not affect the rate of reaction much. All compounds were obtained in good to excellent yield up to 76-92%. The recyclablity of the catalyst was also examined.

Organo‐Catalytic Approach for Biscoumarin Synthesis via a Biomass‐Derived Sustainable Strategy

“…Various reports are there on base catalyzed reactions such as Knoevenagel condensation, Michael addition reaction of C−H active compounds. As mentioned earlier our group has prepared carbohydrate based ionic liquids and examined their catalytic property in various reactions of active methylene compounds and chalcones [47,48] . The mechanism for the synthesis of biscouamrins via one‐pot pseudo three component reaction of 4‐hydroxycoumarin and aldehyde in the presence of catalyst RSIL‐l is outlined in Figure 3.…”

“…As mentioned earlier our group has prepared carbohydrate based ionic liquids and examined their catalytic property in various reactions of active methylene compounds and chalcones. [47,48] The mechanism for the synthesis of biscouamrins via one-pot pseudo three component reaction of 4-hydroxycoumarin and aldehyde in the presence of catalyst RSIL-l is outlined in Thereafter the recyclability of catalyst was also examined through the model reaction. After the reaction was finished, the solid product was filtered, and the filtrate was used in the next reaction.…”

The Synthesis of Nitrogen- and Oxygen-Containing Heterocyclic Scaffolds Assisted by Ionic Liquids: A 2022 Literature Survey

“…Scheme 27 Strecker synthesis of aminonitriles 89 using dicationic imidazolium ILs Garg and Reddy have described the catalytic properties of a biodegradable D-ribose-sugar-based IL (ribose-1-methylimidazolium tosylate) in the synthesis of numerous dihydropyrano coumarin derivatives 90 from coumarin 53, malononitrile (18) and substituted carbaldehydes 87 via Knoevenagel-Michael cyclization (Scheme 28). 85 The maximum yields of 90 were attained at 80 °C after 4 hours. The IL catalyzed the reaction by activating the carbonyl group of 87 to promote its attack on the active methylene 18.…”

“…carbaldehydes (87) via Knoevenagel-Michael-cyclization (Scheme 28). 84 The maximum yields of 90 were attained at 80 o C for 4 h. These ILs catalyzed the reaction by activating carbonyl group of 87 to promote its attack on active methylene of 18. Further, they were reused without major loss of performance up to five cycles.…”

“…The IL formed hydrogen bonds (HBs) bringing 82 and 83 closer to each other for the formation of 84; the reaction mechanism was studied in depth using quantum chemical calculations and density functional theory. Chang and colleagues applied the catalytic properties of the chloroaluminate ILs [bmim][Cl]•xAlCl 3 to prepare 5methyl-3,5-dipropyl-2-pyrazoline (86) from 2-pentyl ketazine (85), wherein the ILs increased the nucleophilicity of the nitrogen atoms through the interaction between the nitrogen of 85 and aluminum to facilitate the intramolecular cyclization of 85 (Scheme 26). 83 Several trials revealed that a temperature of 110 °C and 10 mol% of the ILs were optimum for the synthesis of 86.…”