Recyclable polymer-supported carboxyl functionalized Zn–porphyrin photocatalyst for transfer hydrogenation of levulinic acid to γ-valerolactone

The protocol presents conversion of levulinic acid (LA) to γ-valerolactone (GVL), using polymer-supported carboxyl functionalized Zn–porphyrin (PSCFZnPP) as a photocatalyst under visible light at ambient conditions. The formation of GVL was achieved using 2-propanol as a hydrogen source over PSCFZnPP photocatalyst in a homemade photoreactor under 12-W LED light. The formation of GVL was achieved with 72% yield by transfer hydrogenation in 16 h at room temperature and confirmed by 1 H-NMR and 13 C-NMR at various intervals. The transformation of LA was confirmed by the presence of CH multiplet in 1 H-NMR and deshielding of CH 3 protons in GVL around 1 ppm, after 16 h with disappearance of OH of the substrate. It was further evidenced by the disappearance of ketonic carbonyl C peak height and reduction of LA in 13 C-NMR. Finally, PSCFZnPP exhibited reusability for five times using optimized conditions without significant changes in the yield and structure. Graphical abstract