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  • Title: New polymer-supported mono- and bis-Cinchona alkaloid derivatives: synthesis and use in asymmetric organocatalyzed reactions.
    Author: Jumde RP, Di Pietro A, Manariti A, Mandoli A.
    Journal: Chem Asian J; 2015 Feb; 10(2):397-404. PubMed ID: 25470334.
    Abstract:
    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.
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