A New Annulation Reagent, 2-Oxo-3-alkenylphosphonates. Reactions with Carbonyl-Stabilized Carboanions or Silyl Enol Ethers Leading to Cyclohexanones

Article abstract of DOI:10.1246/bcsj.65.2456

The reactions of 2-oxo-3-alkenylphosphonates with carbonyl-stabilized carbanions directly lead to 2-cyclohexen-1-ones through a sequence of Michael reaction and intramolecular Horner-Emmons olefination.On the other hand, the Lewis acid-mediated reactions with silyl enol ethers produce 1,5-diketones as Michael adducts, which then undergo cyclization on treatment with sodium hydride or triethylamine/zinc (II) bromide to afford 2-cyclohexen-1-ones or 2-phosphinyl-2-cyclohexen-1-ones, respectively.