Wittig Olefination Reaction

The Wittig olefination, or the Wittig reaction, is a classical way to install an olefin group from a parent aldehyde, or in some cases a ketone or other less reactive carbonyl group. The Wittig olefination is incurred using a phosphonium ylide (1), which can exist as a stable compound, or can be generated from a salt form (2) in situ by treatment with base. Wittig reactions often provide the Z-olefin as the exclusive product, but varied conditions can provide the E-olefin product. Because nearly all Wittig reagents are derived from PPh₃, custom or specific phosphonium ylides can be readily synthesized.