Stereo‐ and Chemodivergent NHC‐Promoted Functionalisation of Arylalkylketenes with Chloral. Issue 46 (25th September 2015)

• Record Type: Journal Article
• Authors: Douglas, James J.; Churchill, Gwydion; Slawin, Alexandra M. Z.; Fox, David J.; Smith, Andrew D.
• Is Part Of: Chemistry. Volume 21:Issue 46(2015)
• Page Start: 16354
• Page End: 16358
• Publication Date: 2015-09-25
• Subjects: asymmetric catalysis -- chlorination reactions -- ketenes -- lactones -- stereodivergent reactions; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201503308
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Stereo‐ and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N‐heterocyclic carbenes, giving selectively either β‐lactones (up to 88:12 dr, up to 94 % ee ) or α‐chloroesters (up to 94 % ee ). Either 2‐arylsubstitution or an α‐branched i Pr alkyl substituent within the ketene favours the chlorination pathway, allowing chloral to be used as an electrophilic chlorinating reagent in asymmetric catalysis. Abstract : Taming chloral two ways : Stereo‐ and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N‐heterocyclic carbenes (NHCs), giving selectively either β‐lactones (up to 88:12 dr, up to 94 % ee ) or α‐chloroesters (up to 94 % ee ). Either 2‐arylsubstitution or an α‐branched i Pr alkyl substituent within the ketene favours the chlorination pathway (see scheme).