Wittig Reaction

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This reaction is very complex but extremely useful because it allows us to turn the carbonyl group of aldehydes or ketones, regioselectively, into a double C=C bond.

YouTube video: preparation of alkenes: the Wittig reaction

Wittig reaction: cyclohexanone with the ylide Ph₃P=CH₂ gives methylenecyclohexane

Georg Wittig (1897-1987): Discovered in 1949 his versatile pathway to alkenes from ylides. He received his first education in Tübingen, was director of the Organic Chemistry Department at Heidelberg, where he was emeritus professor from 1967 until the end of his career. In 1967 he won the Otto Hahn Prize and in 1979 shared the Nobel Prize with Herbert C. Brown.

Mechanism of the Wittig reaction: triphenylphosphine and an alkyl halide give the phosphonium salt, whose deprotonation gives the ylide, which attacks the carbonyl to give the alkene and Ph₃P=O

The mechanism of these reactions will be detailed in the chapter of aldehydes and ketones.

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