Synlett 2013; 24(20): 2720-2722
DOI: 10.1055/s-0033-1339893
letter
© Georg Thieme Verlag Stuttgart · New York

Indirect Support for a Stepwise Carbonium Ion Pathway Operating in (4+3)-Cycloaddition Reactions between Furanoxonium Ions and 1,3-Dienes

Matthew J. Palframan
School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK   Fax: +44(115)9513530   Email: gp@nottingham.ac.uk
,
Gerald Pattenden*
School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK   Fax: +44(115)9513530   Email: gp@nottingham.ac.uk
› Author Affiliations
Further Information

Publication History

Received: 23 August 2013

Accepted: 05 September 2013

Publication Date:
14 October 2013 (online)


Abstract

Treatment of solutions of the furfuryl alcohol 6 in dichloromethane–methanol with buta-1,3-diene or cyclohexa-1,3-diene or with cyclopentadiene in the presence of trifluoroacetic acid leads to the corresponding substituted furyl tetrahydrofurans, 8, 12 and 15 respectively, rather than to the products 10, 13 and 16 anticipated from intermolecular (4+3)-type cycloaddition reactions. These outcomes provide indirect experimental support for a stepwise carbonium ion pathway operating in (4+3)-cycloaddition reactions between furanoxonium ions and 1,3-dienes. Alongside other results, the outcomes also highlight a limitation to (4+3) cycloadditions in cycloheptene ring synthesis when the precursors contain hydroxyl groups capable of intercepting any carbonium ion intermediates leading to O-heterocyclic by-products.

Supporting Information

 
  • References

  • 1 For illustrations of the scope for the products of oxidative cleavage of the furan ring in furfuryl alcohols, i.e., the Achmatowicz reaction, in synthesis, see: Burke MD, Berger EM, Schreiber SL. J. Am. Chem. Soc. 2004; 126: 14095 ; and references therein
    • 2a For recent examples of the scope for [5+2]-cycloaddition reactions in synthesis, including natural products, see: Tang B, Bray CD, Pattenden G. Org. Biomol. Chem. 2009; 7: 4448 ; and references therein
    • 2b See also a recent review: Ylijoki KE. O, Stryker JM. Chem. Rev. 2013; 113: 2244

      For examples of the scope of [4+3] cycloadditions in synthesis, see:
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  • 7 Our own DFT calculations were made by Professor Barry Lygo of this School of Chemistry, and will be published separately at a later date.
  • 8 The synthesis of furfuryl alcohol 6 was achieved in three steps from methyl 2-methyl-3-furoate via: (i) an initial Vilsmeier reaction to afford the corresponding aldehyde, (ii) a Wittig reaction with isobutyl(triphenyl)phosphonium iodide, and (iii) a Sharpless dihydroxylation. For full details, see the Supporting Information.
  • 9 For a general experimental procedure for treatment of the vicinal diol based furfuryl alcohol 6 with TFA and a range of dienes, see the Supporting Information.
  • 10 For the synthesis of the acetonide of the furan 22, see reference 5.

    • For recent synthetic applications of (4+3)-type cycloadditions, see:
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