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New Polymer‐Supported Mono‐ and Bis‐ Cinchona Alkaloid Derivatives: Synthesis and Use in Asymmetric Organocatalyzed Reactions
Author(s) -
Jumde Ravindra P.,
Di Pietro Anila,
Manariti Antonella,
Mandoli Alessandro
Publication year - 2015
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201402924
Subject(s) - desymmetrization , cinchona , chemistry , ketene , monomer , enantioselective synthesis , organic chemistry , amination , organocatalysis , enantiomer , polystyrene , yield (engineering) , diethylamine , combinatorial chemistry , catalysis , polymer , materials science , metallurgy
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.