Phosphonic systems. Part 3. Diethyl prop-2-enylphosphonate, a new and versatile substrate in carbon–carbon bond formation
The reactions of lithiated diethyl prop-2-enylphosphonate with α,β-unsaturated ketones and carboxylic esters are described. In simple cases the conjugate addition of the lithium phosphonate via its α- or γ-carbon atom has been observed. In most cases, however, the phosphonate salt has been shown to act as a γ-donor, and a β-acceptor, yielding, in a sequence of reactions, carbocyclic products containing two (or three) new carbon–carbon bonds.