The straightforward synthesis of polystyrene-supported Chinchona alkaloids and their application in the asymmetric dimerization of ketenes is reported. Six different immobilized derivatives, consisting of three dimeric and two monomeric 9-O ethers, were prepared by “click” anchoring of soluble alkaloid precursors on to azidomethyl resins. The resulting insoluble polymer-bound (IPB) organocatalysts were employed for promoting the dimerization of in-situ generated ketenes. After opening of the ketene dimer intermediates with N,O-dimethylhydroxylamine, valuable Weinreb amides were eventually obtained in good yield (up to 81 %) and excellent enantiomeric purity (up to 96 % ee). All of the IPB catalysts could be recycled effectively without significant loss of activity and enantioselectivity. The extension to other asymmetric transformations (meso-anhydride desymmetrization and α-amination of 2-oxindoles) is also briefly discussed.
Autori interni: | MANDOLI, ALESSANDRO (Corresponding) |
Autori: | Jumde, R. P.; Di pietro, A.; Manariti, Antonella; Mandoli, Alessandro |
Titolo: | New Polymer-Supported Mono- and Bis-Cinchona Alkaloid Derivatives: Synthesis and Use in Asymmetric Organocatalyzed Reactions |
Anno del prodotto: | 2015 |
Digital Object Identifier (DOI): | 10.1002/asia.201402924 |
Appare nelle tipologie: | 1.1 Articolo in rivista |
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New Polymer.pdf | Documento in Post-print | Tutti i diritti riservati (All rights reserved) | Open AccessVisualizza/Apri |