Synlett 2013; 24(10): 1243-1249
DOI: 10.1055/s-0033-1338851
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© Georg Thieme Verlag Stuttgart · New York

Enantioselective NHC-Catalysed Formal [4+2] Cycloaddition of Alkylaryl­ketenes with β,γ-Unsaturated α-Ketophosphonates

Stuart M. Leckiea, Charlene Fallana, James E. Taylora, T. Bruce Brownb, David Prydec, Tomáš Lébla, Alexandra M. Z. Slawina, Andrew D. Smith*a
  • aEaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK   Fax: +44(1334)463808   Email: ads10@st-andrews.ac.uk
  • bPfizer Global Research and Development, 388 Ramsgate Road, Sandwich, Kent, CT13 9NJ, UK
  • cPfizer Neusentis, The Portway Building, Granta Park, Great Abington, Cambridge, CB21 6GS, UK
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Publication History

Received: 01 April 2013

Accepted after revision: 03 May 2013

Publication Date:
28 May 2013 (eFirst)

Abstract

NHC-mediated enantioselective formal [4+2] cycloadditions of alkylarylketenes with γ-substituted-β,γ-unsaturated α-ketophosphonates is described. A substrate-dependent switch in diastereoselectivity was observed, with γ-aryl α-ketophosphonates providing preferentially the syn-dihydropyranone-phosphonates and γ-methyl α-ketophosphonates favouring the anti-dihydropyranone-phosphonate. In addition, ketene generation in situ retained high levels of stereoselectivity and led to improved product yields when compared with the corresponding two-step procedure.

Supporting Information