Reactivity of lithium diphenylphosphonium diylides towards phosphorus electrophiles: Synthesis of α,β-unsaturated phosphorus compounds

The study of the reactivity of non-stabilized, semi-stabilized and stabilized lithium diphenylphosphonium diylides 1–4 towards Ph2PCl, allowed the synthesis of various α,β-unsaturated phosphines 13–14, via the intermediate formation of the corresponding functionalized monoylides 9–10 and their in situ reaction with carbonyl compounds. In many cases, the reaction is Z-stereoselective and the created double bond can be di- or also trisubstituted. The precise 1H-NMR study of the phosphines 13a–d and the X-ray analysis of 13a (Z isomer) allowed us to assign without ambiguity the stereochemistry of these compounds and to solve a 1H-NMR question. Contrary to reported results in the literature for 13a, we have shown that for the double bond of this phosphine, there is no exception to the general rule 3JHH(trans)>3JHH(cis). The extension of this reactivity study to other phosphorus electrophiles such as Ph2P(O)Cl, Ph2P(S)Cl and (EtO)2P(O)Cl allowed, as preliminary results, the E-stereoselective synthesis of styrylphosphine oxide and sulfide and diethyl styrylphosphonate.