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1,5-Allyl Shift by a Sequential Achmatowicz/Oxonia-Cope/Retro-Achmatowicz Rearrangement
Xiayan Zhang1,2, Yi Tong1, Gang Li3
1Department of Chemistry, The Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong, China.
Researchers discovered a new 2-step method for a 1,5-allyl shift, overcoming a forbidden rearrangement. This novel organic synthesis technique involves sequential ring expansion and contraction, expanding possibilities in chemistry.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- Allyl shifts via [3,3]- and [2,3]-sigmatropic rearrangements are established synthetic tools.
- The 1,5-allyl shift via [3,5]-sigmatropic rearrangement is thermally forbidden by Woodward-Hoffmann rules.
Purpose of the Study:
- To report the discovery of a novel, formal 1,5-allyl shift.
- To present a new synthetic methodology overcoming a previously unknown rearrangement.
Main Methods:
- A two-step sequential rearrangement process was employed.
- The mechanism involves an Achmatowicz rearrangement (ring expansion) followed by a cascade oxonia-Cope rearrangement/retro-Achmatowicz rearrangement (ring contraction).
Main Results:
- A formal 1,5-allyl shift was successfully achieved for allyl furfuryl alcohol.
- The methodology was demonstrated with over 20 examples, showcasing its versatility.
Conclusions:
- A new pathway for 1,5-allyl shift has been established, circumventing Woodward-Hoffmann restrictions.
- This novel rearrangement offers potential applications in organic synthesis and materials chemistry.
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