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19.5.14.2 Method 2: Wittig Reaction

DOI: 10.1055/sos-SD-019-00220

Murahashi, S.-I.Science of Synthesis, (200419358.

Phosphorus ylides bearing cyano groups can be used for synthesis of α,β-unsaturated nitriles.[‌86‌] Diethyl (cyanomethyl)phosphonates are often allowed to react with aldehydes and ketones in the presence of strong bases such as sodium hydride and sodium amide to give the corresponding α,β-unsaturated nitriles, e.g. 11 (Scheme 20).[‌87‌‌89‌] (Cyanomethyl)triphenylphosphonium salts are useful Wittig reagents bearing cyano groups.[‌90‌,‌91‌] When the phosphine reagent is used in excess, β,γ-unsaturated nitriles are obtained from aliphatic aldehydes.[‌90‌] However, when equimolar amounts of the phosphine and the dithiane are used the α,β-unsaturated nitrile is formed, e.g. 12 (Scheme 20).[‌90‌] Trifluoromethylated pentadienenitriles can also be prepared.[‌92‌]

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