Reaction between 1,2-bis(buta-1,3-dien-1-yl)cyclohexan-1-ol and potassium hydride in THF


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> Which product is formed in the following reaction?
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> [![Reaction between 1,2‐bis(buta‐1,3‐dien‐1‐yl)cyclohexan‐1‐ol and KH in THF at 20 °C](https://i.stack.imgur.com/Qcenu.png)](https://i.stack.imgur.com/Qcenu.png)
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I am quite certain that we deal with an [oxy-Cope rearrangement](https://en.wikipedia.org/wiki/Oxy-Cope_rearrangement) that works at room temperature, but I don’t know how to draw the product given the symmetry.




You are correct, it is indeed an oxy-Cope rearrangement and the macroexpansion gives the 14-membered ketone. From Paquette [[1, p. 13979](https://doi.org/10.1016/S0040-4020(97)00679-0)]:



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> In like fashion, the macroexpansion of **38** and related compounds proceeds in a stepwise manner via enolates **39a** and **39b**. Since **39a** does not accumulate as the reaction proceeds, the second purely Cope rearrangement must be accelerated relative to the first. Trienone **40** has served as a precursor to (+)-muscone and (−)-(3*Z*)-cembrene A.
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> [![Cope rearrangement](https://i.stack.imgur.com/MrY12.png)](https://i.stack.imgur.com/MrY12.png)
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The reaction was reported by Wender et al. [[2, p. 3349](https://doi.org/10.1021/ja00348a072)]:



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> When treated with KH in THF at room temperature, both *trans*- and *cis*-**10** gave a mixture of two *E*/*Z* isomers of the 15-membered tetraeneone **11** (61% and 40%, respectively). Catalytic hydrogenation of this mixture gave a 97% yield of muscone (**12**).
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> [![muscone synthesis](https://i.stack.imgur.com/lVz05.png)](https://i.stack.imgur.com/lVz05.png)
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Structural assignment based on IR and NMR studies suggest the resulting product is the *E*,*E*,*E*-trienone [[3](https://doi.org/10.1016/S0040-4020(01)93271-5)]. The process of ring expansion via Cope rearrangement appears to be initially investigated by Cookson and Singh in late 1960s in the context of obtaining macrocyclic musk ketone [[4](https://doi.org/10.1039/j39710001477)]:



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> Reaction of the keto-allene (**III**) with vinylmagnesium bromide in tetrahydrofuran gave the vinyl alcohol (**VII**) in good yield.
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> …compound (**VII**) undergoes Cope rearrangement to the enol of (**VIII**) before it fragments. Complete rearrangement through to the ketone (**VIII**) before fragmentation cannot have occurred, for there
> were distinct differences in the mass spectra of the alcohol (**VII**) and ketone (**VIII**)…
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> The compound (**VII**) though fairly stable, showed the appearance of a carbonyl band, evidently by rearrangement to (**VIII**), when left for a prolonged period.
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> [![allenic ketone undergoes thermal Cope rearrangement to
> 4-isopropylidenecyclohexadec-5-trans-enone](https://i.stack.imgur.com/X3ETt.png)](https://i.stack.imgur.com/X3ETt.png)
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### References


1. Paquette, L. A. Recent Applications of Anionic Oxy-Cope Rearrangements. *Tetrahedron* **1997**, 53 (41), 13971–14020. DOI: [10.1016/S0040-4020(97)00679-0](https://doi.org/10.1016/S0040-4020(97)00679-0).
2. Wender, P. A.; Holt, D. A.; Sieburth, S. M. Practical Method for α-Alkenyl Ketone Synthesis Based on a Facile Reductive Rearrangement of Alkynyl Halohydrins. *J. Am. Chem. Soc.* **1983**, 105 (10), 3348–3350. DOI: [10.1021/ja00348a072](https://doi.org/10.1021/ja00348a072).
3. Wender, P. A.; Sieburth, S. McN.; Petraitis, J. J.; Singh, S. K. Macroexpansion Methodology. *Tetrahedron* **1981**, 37 (23), 3967–3975. DOI: [10.1016/S0040-4020(01)93271-5](https://doi.org/10.1016/S0040-4020(01)93271-5).
4. Cookson, R. C.; Singh, P. Expansion of the Ring of Cyclododecanone by Two and Four Carbon Atoms. *J. Chem. Soc., C* **1971**, 1477. DOI: [10.1039/j39710001477](https://doi.org/10.1039/j39710001477).


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