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Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments
Published on: May 11, 2017
Mixed alkylamido aluminate as a kinetically controlled base.
Hiroshi Naka1, James V Morey, Joanna Haywood
1Graduate School of Pharmaceutical Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai 980-8578, Japan. naka@mail.pharm.tohoku.ac.jp
Journal of the American Chemical Society
|November 8, 2008
Summary
Directed ortho metalation (DoM) using TMP-aluminate was investigated. Computational and X-ray studies revealed kinetic barriers, showing ortho-aluminated aromatics resist further deprotonation, unlike ortho-zincated compounds.
Area of Science:
- Organometallic Chemistry
- Organic Synthesis
- Computational Chemistry
Background:
- Directed ortho metalation (DoM) is a key strategy for functionalizing aromatic compounds.
- Mixed alkylamido aluminates, such as TMP-aluminate, are increasingly used in DoM reactions.
- Understanding the mechanisms of metalation and postmetalation is crucial for synthetic applications.
Purpose of the Study:
- To investigate the mechanisms of directed ortho metalation (DoM) and postmetalation processes using TMP-aluminate.
- To elucidate the structural and reactivity characteristics of ortho-aluminated aromatic intermediates.
- To compare the reactivity of ortho-aluminated aromatics with related ortho-zincated systems.
Main Methods:
- X-ray diffraction to determine the structure of key intermediates.
- Density functional theory (DFT) calculations to explore reaction pathways and kinetic barriers.
- Sequential reactions involving aromatic compounds, t-BuLi, and i-Bu3Al.
Main Results:
- Structural evidence for ortho-aluminated functionalized aromatics was obtained, serving as model intermediates.
- Ortho-aluminated aromatics were found to resist reaction with HTMP, indicating an inability for stepwise deprotonative reactivity.
- DFT calculations revealed significant kinetic barriers to alkyl exchange and amido-alkyl exchange.
- The Lewis acidity of aluminum centers was rationalized as the cause for this reactivity difference compared to zinc.
Conclusions:
- TMP-aluminate exhibits unique reactivity in DoM, distinct from ortho-zincation chemistry.
- Kinetic barriers prevent further deprotonation of ortho-aluminated intermediates.
- The study provides a mechanistic understanding of DoM with TMP-aluminate and its synthetic utility.
- This research enables highly regioselective deprotonative functionalization of unsymmetrical ketones.
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