Stable complex formation with boric acid in pyrolysis of levoglucosan in acidic media

✍ Scribed by H. Kawamoto; S. Saito; S. Saka

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 490 KB
• Volume: 82
• Category: Article
• ISSN: 0165-2370
• DOI: 10.1016/j.jaap.2007.12.008

✦ Synopsis

The influence of boric acid or phenylboronic acid on thermal conversion of levoglucosan in acidic sulfolane was studied. Although levoglucosan was converted to levoglucosenone, furfural and 5-hydroxymethyl furfural (total yield: 40 mol%) at 200 8C in sulfolane containing 0.1 wt% H 2 SO 4 , addition of boric acid enormously lowered the yields of these, and instead caused the formation of a stable complex in more than 70 mol% yield. Thus, boric acid substantially suppressed the acid-catalyzed dehydration and formation of furfurals from levoglucosan through complex formation. From the 1 H NMR spectrum, the chemical structure of this complex was confirmed as a-D-glucofuranose cyclic 1,2:3,5bisborate, which was readily hydrolyzed quantitatively to glucose by the addition of water. Phenylboronic acid also exhibited similar influences.