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Item Aqueous solution of biogenic carboxylic acids as sustainable catalysts and green reaction media for the high-yielding synthesis of Biginelli adducts, Hantzsch esters, and substituted pyridines(Royal Society of Chemistry, 2024) Prabhakar, P.S.; Sahoo, J.; Alnaser, I.A.; Seikh, A.H.; Karim, M.R.; Dutta, S.3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) and 1,4-dihydropyridines (DHPs), prepared by applying the Biginelli and Hantzsch reaction protocols, respectively, are well-documented nitrogen-containing heterocycles with intriguing pharmacological properties. The aqueous solution of biogenic carboxylic acids renewably produced from biomass via catalytic or enzymatic processes can be used as a sustainable catalyst and green reaction media for synthesizing DHPs and DHPMs. This work evaluates the efficacy of various biogenic acids in their aqueous solutions as catalysts for synthesizing DHPs and DHPMs from substituted benzaldehydes. Among the studied biogenic acids, gluconic acid aqueous solution (GAAS) proved to be the most efficient, safe, non-volatile, and recyclable catalyst. The reaction afforded excellent isolated yields (≥85%) of spectroscopically pure DHPs and DHPMs under optimized conditions and employed a straightforward work-up procedure. Aqueous ammonia was successfully employed instead of ammonium salt to improve the atom economy of DHPs. Moreover, substituted pyridines were synthesized from DHPs in a one-pot, two-step process using NaNO2 as an oxidant in the GAAS medium. This journal is © The Royal Society of Chemistry, 2024Item Extending the Carbon Chain Length of Carbohydrate-Derived 5-Substituted-2-furaldehydes by Condensing with Active Methylene Compounds under Organocatalytic Conditions(American Chemical Society, 2024) Prabhakar, P.S.; Seikh, A.H.; Karim, M.R.; Dutta, S.This work reports a high-yielding, organic solvent-free, gram-scale synthesis of novel Knoevenagel condensation products by reacting carbohydrate-derived 5-substituted-2-furaldehydes (SFLs) with active methylene compounds (AMCs) using various organic amines and inorganic bases as catalysts. Among the base catalysts examined, piperidine performed best, affording satisfactory selectivity and yield of the targeted Knoevenagel condensation products owing to the subtle balance between its nucleophilicity and basicity. The reaction was optimized on various reaction parameters, such as temperature, duration, solvent, catalyst loading, and molar ratio of the reactants. Even though the SFLs exhibited significantly different reactivity, a general synthetic protocol was developed successfully, affording good to excellent isolated yields (70-96%) of the novel Knoevenagel condensation products at ambient temperature. Moreover, the Knoevenagel products were purified by triturating with eco-friendly solvents (e.g., ethyl acetate and n-heptane) without chromatographic purification. © 2024 The Authors. Published by American Chemical Society.