Oxidative Coupling of Aldehydes with Alcohol for the Synthesis of Esters Promoted by Polystyrene-Supported N-Heterocyclic Carbene: Unraveling the Solvent Effect on the Catalyst Behavior Using NMR Relaxation

[Image: see text] Heterogeneous organocatalysts hold great potential as they offer practical advantages in terms of purification and reusability compared with the homogeneous counterpart. A puzzling aspect is the solvent effect on their catalytic performance. Here we propose a new approach whereby T(1)/T(2) NMR relaxation measurements are used to evaluate the strength of solvent–surface interactions in the polystyrene-supported N-heterocyclic carbene-promoted oxidation of aldehydes. The results reveal that solvents with high surface affinity lead to a decrease in catalyst activity.