Abstract
Air-stable dimethylaluminum complexes LRAlMe2 that contain (aminomethyl)phenolate (LR) ligands were prepared in high yield. NMR data and X-ray crystallographic characterization of the molecular structures of several of the complexes confirmed bidentate coordination of the (aminomethyl)phenolate ligand to aluminum. Efficient aluminum catalysts for glucose dehydration to HMF were generated via modification of the (aminomethyl)phenolate ligand. LRAlMe2 complexes containing bidentate (aminomethyl)phenolate ligands with an aryl substituent on the amino moiety are efficient catalysts for glucose dehydration to HMF in ionic liquid solvents. In [EMIM]Br and [BMIM]Br, the reaction proceeds at 120 °C to very high conversion in 2 h to produce HMF with 60–63% selectivity and in 58–60% yield. Evidently, LRAlMe2 complexes catalyze glucose isomerization to fructose at ≥120 °C while the HMF yield depends on the degree of competing HMF loss to humins formation. These results indicate that additional studies of ancillary ligand effects on aluminum-catalyzed glucose dehydration are needed to improve knowledge of structure–function relationships that are key to increasing the efficiency of aluminum catalysts for dehydration of glucose (and ultimately cellulose) to HMF.
Original language | English |
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Pages (from-to) | 153-162 |
Number of pages | 10 |
Journal | Polyhedron |
Volume | 149 |
DOIs | |
State | Published - Jul 15 2018 |
Bibliographical note
Funding Information:We are grateful to the Kentucky Science Foundation (grant number KSEF-2428-RDE-014 ) for partial financial support of this work. We are also grateful to US National Science Foundation (grant number CBET 1604491 ) for partial financial support of this research. NMR instruments utilized in this research were funded in part by the CRIF program of the US National Science Foundation (grant number CHE-9974810 ). The X8 Proteum and D8 Venture diffractometers were funded by the NSF (MRI CHE0319176 and CHE1625732 respectively). The authors are also grateful to Professor Darrin L. Smith (Chemistry Department, Eastern Kentucky University) for generously providing access and helping with HPLC analysis. DS is grateful to Professor Anne-Frances Miller and Mr. John Layton for helpful advice with regard to NMR.
Funding Information:
We are grateful to the Kentucky Science Foundation (grant number KSEF-2428-RDE-014) for partial financial support of this work. We are also grateful to US National Science Foundation (grant number CBET 1604491) for partial financial support of this research. NMR instruments utilized in this research were funded in part by the CRIF program of the US National Science Foundation (grant number CHE-9974810). The X8 Proteum and D8 Venture diffractometers were funded by the NSF (MRI CHE0319176 and CHE1625732 respectively). The authors are also grateful to Professor Darrin L. Smith (Chemistry Department, Eastern Kentucky University) for generously providing access and helping with HPLC analysis. DS is grateful to Professor Anne-Frances Miller and Mr. John Layton for helpful advice with regard to NMR.
Publisher Copyright:
© 2018
Keywords
- 5-Hydroxymethylfurfural
- Aluminum catalysts
- Dehydration
- Glucose
- Ionic liquids
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry