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.

New Polymer-Supported Mono- and Bis-Cinchona Alkaloid Derivatives: Synthesis and Use in Asymmetric Organocatalyzed Reactions

MANARITI, ANTONELLA;MANDOLI, ALESSANDRO
2015

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.
Jumde, R. P.; Di pietro, A.; Manariti, Antonella; Mandoli, Alessandro
File in questo prodotto:
File Dimensione Formato  
New Polymer.pdf

accesso aperto

Tipologia: Documento in Post-print
Licenza: Tutti i diritti riservati (All rights reserved)
Dimensione 2.12 MB
Formato Adobe PDF
2.12 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/677664
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 23
  • ???jsp.display-item.citation.isi??? 22
social impact