Cellulose@PO3H: As an Efficient and Recyclable Ionic Liquid-Enabled Catalytic Greener Approach to One-Step Synthesis of Flavoring Ketones

Cellulose (CL) is widely available from the renewable biomaterial on the earth with a large number of hydroxyl functionalities on its surface. The appropriate modification of these functionalities results in the acidic and basic nature of the surface. In this work, the phosphoric group-functionalized CL ionic liquid (IL) has been successfully synthesized through phosphorylation of the CL surface. The phosphorus functionalization of CL has been carried out in two steps; first, synthesis of IL (3, 5-lutidinium methyl phosphate [Lut]­[(MeO)­(H)­PO2]), followed by phosphorylation of cellulose (CLP-IL). Subsequently, CLP-IL has been characterized by various physicochemical techniques. Significant changes in the activity were observed, with marginal changes in the structural and morphological properties of the native CL. CLP-IL has been utilized to synthesize industrially important flavoring ketones (FKs) via one-step alkylation–decarboxylation of active methylene compounds with substituted benzyl alcohols and halides. The functionalized CL IL could be quickly recovered in water and recycled at least five times without losing the catalytic activity. The optimized protocol has been successfully employed for the synthesis of FKs with an excellent conversion of substituted benzyl carbons in the range (90–100%) with 70–90% isolated yield of desired market valuable products. Furthermore, the mechanism was established by identifying the intermediates by physicochemical methods.