2,3-sigmatropic rearrangement

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2,3-Sigmatropic rearrangements are a type of

anionic.[1]
The general scheme for this kind of rearrangement is:

Atom Y may be sulfur, selenium, or nitrogen. If Y is nitrogen, the reaction is referred to as the Sommelet–Hauser rearrangement if a quaternary ammonium salt is involved or the aza-Wittig reaction if an alpha-metalated tertiary amine is involved; if Y is oxygen, then it is called a 2,3-Wittig rearrangement (not to be confused with the well-known Wittig reaction, which involves a phosphonium ylide). If Y is sulfur, the product can be treated with a thiophil to generate an allylic alcohol in what is known as the Mislow–Evans rearrangement.

A [2,3]-rearrangement may result in carbon-carbon bond formation. It can also be used as a

ring-expansion reaction.[2]

Stereoselectivity

2,3-sigmatropic rearrangements can offer high

syn
product.

endo
orientation in transition state.

References