C₆-Aldehyde Functionalized Cellulose Preparation by 2-Iodoxybenzoic Acid Oxidation

Selective oxidation of polyol-containing cellulose is significant for the development of cellulose-derived functional materials. While conventional oxidation methods readily introduce aldehyde groups at the C₂/C₃ positions (accompanied by ring-opening of anhydroglucose units) or carboxyl groups at the C₆ positions in cellulose, selective oxidation to generate aldehyde functionalities specifically at the C₆ position remains challenging. Herein, we demonstrate that 2-Iodoxybenzoic acid (IBX) acts as an efficient and selective oxidant for converting the primary alcohol at the C₆ position of anhydroglucose units to aldehyde groups under mild conditions. Monosaccharide model studies confirmed C₆-specific oxidation. This method was successfully applied for the surface modification of microcrystalline cellulose (MCC, predominantly Iβ allomorph) and bacterial cellulose (BC, mainly Iα allomorph), achieving aldehyde contents of 0.96 and 0.93 mmol g-1, respectively, with 0.6 and 0.5 equiv of IBX per anhydroglucose unit. Crystallinity analysis showed that oxidation with IBX leads to a significant decrease of crystallinity but has a negligible effect on the cellulose allomorph. This study presents a novel approach for the preparation of C₆-aldehyde cellulose, enabling precise, selective modification and advancing functional material development.