Abstract
General routes for the synthesis of silica-immobilized symmetrical and unsymmetrical salophen and salen ligands and metal complexes have been developed starting from the natural product 4-allylanisole (methyl-chavicol and estragole). The key step of the syntheses is a microwave-assisted, platinum oxide catalyzed hydrosilylation of the terminal alkene of 5-allyl-2-hydroxybenzaldehyde to afford a sol-gel precursor which can be immobilized into silica before or after conversion to salen and salophen ligands to afford unsymmetrical and symmetrical silica-supported ligands, respectively. Both the symmetrical and unsymmetrical silica-supported salophens were found to catalyze the formation of cyclic carbonates from epoxides and carbon dioxide with catalytic activities at least comparable to those previously reported for non-immobilized homogeneous salophens. This reaction could also be carried out in a multi-phase flow reactor using ethyl acetate solutions of 3-phenoxypropylene oxide. Metal complexes of the silica-immobilized ligands could be prepared, and the aluminum complexes were also found to catalyze cyclic carbonate formation.
| Original language | English |
|---|---|
| Pages (from-to) | 16410-16423 |
| Journal | Journal of Organic Chemistry |
| Volume | 87 |
| Issue number | 24 |
| Early online date | 1 Dec 2022 |
| DOIs | |
| Publication status | Published - 16 Dec 2022 |
Bibliographical note
© 2022 The Authors. Published by American Chemical Society.Funding Information:
Royal Society International Collaboration Award IC170051 to MN and CJAM. Chinese Scholarship Council Award 201908330607 to LG