Abstract

This paper details the enantioselective performance of styrene/divinylbenzene-supported Mn- and Cr-based salen complexes for the epoxidation of olefins and the ring-opening of epoxides to azido-silyl ethers. The Mn catalyst produced the epoxides of 1,2-dihydronaphthalene, styrene, and cis-β-methylstyrene with enantiomeric excesses (ee's) of 46, 9, and 79%, respectively. For the Cr catalyst, the enantioselective ring-opening of epoxyhexane, propylene oxide, and cyclohexene oxide with trimethylsilyl azide proceeded with ee's of 34, 36, and 6%, respectively. Upon recycle of these heterogeneous catalysts, a degradation process was noted for the Mn-catalyst under the conditions for epoxidation that resulted in oxidation and decomposition of the ligand. This process also affects the homogeneous catalyst, thereby limiting the recyclability of both the homogeneous Mn catalyst and its heterogenized version for this reaction. The Cr-catalyzed reaction to ring-open epoxides employs milder conditions and allowed reuse of the heterogeneous catalyst without loss of activity or enantioselectivity through three runs with epoxyhexane. During reaction, the leaching of Cr from the heterogeneous catalyst is less than 0.1%, suggesting possible reuse of the catalyst over hundreds of cycles before reloading the polymer-supported salen ligand with metal would be necessary. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3888–3898, 1999

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.