Acylation of Cellulose with N,N 0 -Carbonyldiimidazole- Activated Acids in the Novel Solvent Dimethyl Sulfoxide/Tetrabutylammonium Fluoride Muhammad Ajaz Hussain, Tim Liebert, Thomas Heinze* Kompetenzzentrum Polysaccharidforschung an der Friedrich-Schiller-Universita ¨t Jena, Lessingstrasse 8, D-07743 Jena, Germany Fax: 0049 3641/644020; E-mail: thomas.heinze@uni-jena.de Received: December 18, 2003; Revised: January 29, 2004; Accepted: January 30, 2004; DOI: 10.1002/marc.200300308 Keywords: biopolymers; carboxylic acids; cellulose functionalization; esterification; homogeneous reaction; NMR Introduction The preparation of cellulose derivatives with tailored pro- perties, e.g., for application in biotechnology or sensor tech- niques, is a major stimulation for the search of new solvents and reagents in polysaccharide chemistry. These new tools may lead to unconventional synthesis pathways and deriva- tives not yet accessible. [1–3] The most versatile and interesting types of cellulose solvents for the modification are binary mixtures of polar organic liquids and inorganic salts. Typical examples are N,N-dimethylacetamide (DMAc) or its cyclic analogue 1-methyl-2-pyrrolidinone in combination with LiCl. [4] Recently, the mixture dimethyl sulfoxide (DMSO)/tetra- butylammonium fluoride trihydrate (TBAF) was found to be a very efficient solvent for cellulose, which is increas- ingly studied as a reaction medium. [5–8] DMSO/TBAF dissolves cellulose without any pre-treatment within minu- tes. It has been exploited for acylation reactions using acid anhydrides and vinyl esters. A promising new synthesis path is the homogeneous, one-pot esterification of cellulose with carboxylic acids after in-situ activation. Reagents exploited for this functio- nalization strategy are p-toluenesulfonyl chloride [9–12] and 1,3-dicyclohexylcarbodiimide (DCC) in combination with 4-pyrollidinopyridine (PP). [13] It was found that during tosyl chloride activation, the carboxylic acid chloride and the symmetric anhydride are formed which results in a high reactivity but remarkable side reactions, e.g., degradation of the polymer occurs. [2] The drawback in the case of DCC is its high toxicity. For the first time we applied N,N 0 -carbonyldiimidazole (CDI) as an activating agent for the homogeneous cellulose acylation. The advantages are mild reaction conditions, limited amounts of by-products (which are non-toxic and reusable [14] ), and commercial availability of the reagents. Here we report on the simple, efficient, and mild homo- geneous synthesis of pure aliphatic, alicyclic, bulky, and unsaturated cellulose esters using CDI as activating agent and DMSO/TBAF as solvent. Experimental Part Materials The cellulose Avicel 1 PH-101 (degree of polymerization, DP, 260) was dried under vacuum at 110 8C for 8 h before use. The Summary: Carboxylic acids were efficiently activated with N,N 0 -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 ali- phatic, 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 N,N-dimethylformamide (DMF). The cellulose esters were characterized by elemental analysis, FT-IR, 1 H and 13 C NMR spectroscopy and show no impurities or substructures resulting from side reactions. The esterification of cellulose using carboxylic acids activa- ted in situ with N,N 0 -carbonyldiimidazole. Macromol. Rapid Commun. 2004, 25, 916–920 DOI: 10.1002/marc.200300308 ß 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 916 Communication