Science of Synthesis

Göttlich, R., Science of Synthesis, (2007) 25, 384.

The conjugate addition of carbon-centered radicals to α,β-unsaturated alkenes is a very common process in radical chemistry. Electron-withdrawing substituents activate alkenes to radical addition. The two most common methods in this context, the addition of alkylmercury hydrides and the addition of alkyl radicals derived from alkyl halides using tin hydrides (or less-toxic silanes), are both known as the “Giese reaction”.[‌100‌,‌101‌] Even though Giese successfully added an alkylmercury hydride to an α,β-unsaturated aldehyde in 74% yield,[‌102‌] and this type of chemistry continued to be used for some time,[‌103‌,‌104‌] the toxicity of alkylmercury compounds is a considerable drawback. The tin hydride method, on the other hand, produces only low yields with α,β-unsaturated aldehydes (e.g., 30–50% in a typical example),[‌105‌] probably as a result of a competing reduction of the aldehyde by the reagent.[‌106‌] Efficient methods for radical addition to α,β-unsaturated aldehydes are therefore limited to the addition of organoboranes (the Brown reaction; see Section ‌25.1.15.3.1‌) and the Meerwein arylation reaction (see Section ‌25.1.15.3.2‌).

References

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• 8.Meeeee-Meee, (8888) 8/8, 888.