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26.1.8.4 Method 4: Fragmentation of α,β-Unsaturated Ketones (Eschenmoser Fragmentation)

DOI: 10.1055/sos-SD-026-00328

Constantieux, T.; Rodriguez, J.Science of Synthesis, (200526425.

The transformation of α,β-unsaturated ketones, via the fragmentation of their α,β-epoxy hydrazone derivatives, is a very useful procedure for the synthesis of alkynones. In pioneering works, tosylhydrazones were first used by Eschenmoser,[‌68‌‌70‌] and later, ­independently, by Tanabe.[‌71‌,‌72‌] The fragmentation of these substrates gives four parts, a ketone, an alkyne, nitrogen, and 4-toluenesulfonic acid. If both the ketone and alkyne moieties are connected, this methodology allows efficient entry to acyclic or cyclic ­alkynones. The transformation may be viewed as outlined in Scheme 21.

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