2,6-Disubstituted Tetrahydropyrans by Domino Meyer-Schuster Rearrangement-Hetero-Michael Addition of 6-Alkyne-1,5-diols

Starting from pentanediol various oct-6-yne-1,5-diols were prepared. In the presence of catalytic amounts of an Au(I) or Pt(II) catalyst transformation to cis-2,6-tetrahydropyrans was observed. It is assumed that this novel domino sequence proceeds via an initial Meyer-Schuster rearrangement of the propargylic alcohol yielding a hydroxyenone that undergoes an intramolecular oxa-Michael addition through a chairlike transition state to the tetrahydropyran system.