Reaction of dialdehydes with conventional and polymer-supported Wittig reagents

Olefinizations carried out under a variety of conditions, using a 1 : 1 molar ratio of polymer-supported Wittig reagent to dialdehyde (terephthalaldehyde and isophthalaldehyde), lead exclusively to monocondensation products. Results in conventional reactions, depend on the particular Wittig reagent employed, the procedure used, and the halide counterion which is present; when using ethylene oxide as base, chloride ion favours mono-olefinizations. In solid phase Wittig reactions, with ethylene oxide as base and bromide as the counterion, monoethylene acetal formation becomes an important by-reaction.