Synlett 1989; 1989(1): 15-18
DOI: 10.1055/s-1989-34701
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η5-Cyclopentadienylcobalt-Mediated Inter- and Intramolecular [2+2+2] Cycloadditions of Alkynes to Aldehydes and Ketones: A Novel Synthesis of Fused 2H-Pyrans

Daniel F. Harvey* , Barry M. Johnson, Christopher S. Ung, K. Peter C. Vollhardt
  • *Department of Chemistry, University of California at Berkeley, and the Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720, USA
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Publication History

Publication Date:
26 February 2002 (online)

η5-Cyclopentadienylcobalt complexes induce the cocyclization of alkynes with aldehydes and ketones to furnish mainly complexed bi- and tricyclic 2H-pyrans (7 examples) and/or their α, β, γ, δ-unsaturated carbonyl isomers (7 examples). The latter are derived formally from the former by electrocyclic ring-opening, in three cases possibly preceded by [1,5] hydrogen shifts.