Carboxylic acids were efficiently activated with N,N'-carbonyldiimidazole (CDI) and applied for the acylation of cellulose under homogeneous conditions using dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF) as solvent. The simple and elegant method is a very mild and easily applicable tool for the synthesis of pure aliphatic, alicyclic, bulky, and unsaturated cellulose esters with degrees of substitution of up to 1.9. Products are soluble in organic solvents, e.g., DMSO or NN-dimethylformamide (DMF). The cellulose esters were characterized by elemental analysis, FT-IR, H-1 and C-13 NMR spectroscopy and show no impurities or substructures resulting from side reactions.