Science of Synthesis

Watson, I. D. G.; Toste, F. D., Science of Synthesis: Stereoselective Synthesis, (2011) 3, 243.

The quintessential cycloisomerization reaction is the intramolecular Alder-ene reaction of 1,n-enynes. As the alkyne variant of the ene reaction (‌Scheme 1‌), this reaction has been known since the 1940s in its uncatalyzed, thermal form.[‌12‌] This classic process involves the reaction of an alkene containing an allylic hydrogen (the ene) with an alkyne (the enophile). The result is a six-electron pericyclic rearrangement causing the formation of two σ bonds (‌Scheme 1‌). The thermal reaction, in the absence of a transition metal, has had few applications in organic synthesis. This is presumably due to limitations in its scope, since high temperatures are required.

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References