Efficient, Regioselective Design of Mixed Cellulose Esters and Macroinitiators

Mixed cellulose esters and macroinitiators with high C6-OH regioselectivity were synthesized by employing a tritylation protecting strategy, using sequential one-pot protection/acylation and deprotection/reacylation transformations, reducing the number of overall discrete steps and product isolations by half. This method produced organosoluble 2,3-di-<i>O</i>-acyl-6-<i>O</i>-(4-monomethoxytrityl) (2,3A-6MeOTr) cellulose intermediates, simplifying the generation of regioselectively substituted cellulose esters with controllable degree of substitution (DS) and substitution position. Treatment of 2,3A-6MeOTr celluloses with carboxylic acid anhydrides and trifluoroacetic acid (TFA) or acyl halides resulted in one-pot detritylation and reacylation of protected C6-OH groups without acyl migration or significant backbone degradation. Thermal analysis indicated that both DS and C6 compositions affected the glass transition temperature (<i>T</i>_g) of mixed cellulose esters, highlighting the value of this method for structure-property relationship elucidation. Notably, mixed 2,3-di-<i>O</i>-A-6-<i>O</i>-B (2,3A-6B) cellulose esters with DS(A) > 2.69 were semicrystalline. This method permits the facile generation of regioselectively substituted 2,3A-6B cellulose esters, including well-defined macroinitiators for controlled radical polymerization.