Conjugate addition of alcohols in the presence of triethylamine, followed by elimination and removal of the second phosphonium salt by base-induced cleavage, leads to vinyl ethers: Synthesis, 736 (1975). Similarly, other nucleophiles (e.g. phenols or thiols) can be used to replace one of the phosphonium groups by addition-elimination: Bull. Soc. Chim. Fr., 1421 (1974). With bifunctional nucleophiles, cyclization can occur to give an intermediate for the formylolefination of aldehydes by the Wittig reaction.Synthesis, 826 (1978).
