title: Remarkably regioselective deacylation of cellulose esters using tetraalkylammonium salts of the strongly basic hydroxide ion.
abstract: Tetraalkylammonium hydroxides have been found to mediate regioselective deacylation of cellulose esters. This deacylation surprisingly shows substantial selectivity for the removal of the acyl groups at O-2/3, affording cellulose-6-O-esters by a simple, efficient one-step process. The mechanism for this deacylation was investigated by studying the effect of tetraalkylammonium cation size upon ester deacylation selectivity. We hypothesize that coordination of the tetraalkylammonium cation by the ester oxygen atoms of the vicinal 2,3-acetate groups may drive the unexpected regioselectivity at the secondary alcohol esters. Broad scope with respect to ester type was demonstrated; regioselective O-2,3 deacylation was observed with cellulose acetate, propionate, butyrate, hexanoate and benzoate triesters. The scope of this deacylation of cellulose acetates has been investigated to understand how to carry it out most efficiently. Reaction with TBAOH in pyridine was the most effective process, providing the highest selectivity.
authors.affiliation: Department of Sustainable Biomaterials, Virginia Tech, 230 Cheatham Hall, 310 West Campus Drive, Blacksburg, VA 24061, United States; Department of Chemistry, Virginia Tech, 230 Cheatham Hall, 310 West Campus Drive, Blacksburg, VA 24061, United States.
authors.forename: Xueyan
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, Virginia Tech, 230 Cheatham Hall, 310 West Campus Drive, Blacksburg, VA 24061, United States.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Gandour
authors.affiliation: Department of Sustainable Biomaterials, Virginia Tech, 230 Cheatham Hall, 310 West Campus Drive, Blacksburg, VA 24061, United States; Department of Chemistry, Virginia Tech, 230 Cheatham Hall, 310 West Campus Drive, Blacksburg, VA 24061, United States; Macromolecules and Interfaces Institute, Virginia Tech, 230 Cheatham Hall, 310 West Campus Drive, Blacksburg, VA 24061, United States. Electronic address: kjedgar@vt.edu.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Edgar
mesh_terms: D000215:Acylation; D000478:Alkylation; D064751:Ammonium Compounds / Q000737:chemistry*; D002384:Catalysis; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D006868:Hydrolysis; D006878:Hydroxides / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D064751:Ammonium Compounds; D004952:Esters; D006878:Hydroxides; D012492:Salts; C005062:acetylcellulose; D002482:Cellulose; C031356:hydroxide ion
keywords: Cellulose ester; Deacylation; Hydrolysis; Mechanism; Regioselectivity