Hydroboration-oxidation: A chemoselective route to cellulose ω-hydroxyalkanoate esters.
We describe the first synthesis of hydroxy-functionalized polysaccharide esters via chemoselective olefin hydroboration-oxidation in the presence of ester groups. Cellulose esters with terminally olefinic side chains were first synthesized by esterification of commercially available cellulose esters (e.g., cellulose acetate) with undec-10-enoyl chloride or pent-4-enoyl chloride. Subsequent two-step, one-pot hydroboration-oxidation reactions of the cellulose esters were performed, using 9-borabicyclo[3.3.1]nonane as hydroboration agent, followed by oxidizing the intermediate borane to a hydroxyl group using mildly alkaline H2O2. Sodium acetate was used as a weak base to catalyze the oxidation, thereby minimizing undesired ester hydrolysis. Characterization methods including FTIR, (1)H, and (13)C NMR proved the selectivity of the hydroboration-oxidation pathway, providing a family of novel cellulose ω-hydroxyalkanoyl esters that were previously difficult to access.
Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, USA; Department of Sustainable Biomaterials, Virginia Tech, Blacksburg, VA 24061, USA.
Xiangtao
X
Meng
Department of Chemistry, Biochemistry and Physics, Niagara University, Lewiston, NY 14109, USA.
Emily A
EA
York
Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, USA; Department of Chemistry, Virginia Tech, Blacksburg, VA 24061, USA.
Shu
S
Liu
Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, VA 24061, USA; Department of Sustainable Biomaterials, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address: kjedgar@vt.edu.
Kevin J
KJ
Edgar
D000475:Alkenes / Q000737:chemistry; D002482:Cellulose / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D006860:Hydrogen Bonding; D006868:Hydrolysis; D010084:Oxidation-Reduction
D000475:Alkenes; D004952:Esters; D002482:Cellulose
9-BBN; Alcohol; Cellulose ester; Hydroboration; Olefin; Sodium acetate