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2,3-sigmatropic rearrangements can offer high stereoselectivity. At the newly formed double bond there is a strong preference for formation of the E-alkene or trans isomer product. The stereochemistry of the newly formed C-C bond is harder to predict. It can be inferred from the five-membered ring transition state.
The Cope rearrangement is an extensively studied organic reaction involving the [3,3] sigmatropic rearrangement of 1,5-dienes. [ 14 ] [ 15 ] [ 16 ] It was developed by Arthur C. Cope . For example, 3,4-dimethyl-1,5-hexadiene heated to 300 °C yields 2,6-octadiene.
In [1,j]-sigmatropic rearrangements if j + 1 = 4n, then supra/antara is thermally allowed, and if j + 1 = 4n + 2, then supra/supra or antara/antara is thermally allowed. [20] The other prevalent class of sigmatropic rearrangements are [3,3], notably the Cope and Claisen rearrangements. Here, the constructive interactions must be between the ...
[2,3]-Sigmatropic rearrangements occur for a variety of groups X and Y (see below).When X is a carbanion and Y an alkoxide, the rearrangement is called the [2,3]-Wittig rearrangement and the products are pent-1-en-5-ols.
In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. [1] Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular.
A key step in the synthesis is the rhodium-catalyzed formation of an oxonium ylide, which then undergoes a [2,3] sigmatropic rearrangement en route to the desired product. [22] However, the substrate contains two ortho-alkoxy groups, either of which could presumably participate in oxonium ylide generation.
The [2,3]-sigmatropic rearrangement of the thiophenyl group to give the sulfoxide as below proceeded enantiospecifically due to the predefined stereochemistry of the propargylic alcohol. In this way, the single allene isomer formed could direct the Diels–Alder reaction to occur on only one face of the generated 'diene'.
The Mislow–Evans rearrangement is a name reaction in organic chemistry. It is named after Kurt Mislow who reported the prototypical reaction in 1966, [1] and David A. Evans who published further developments. [2] The reaction allows the formation of allylic alcohols from allylic sulfoxides in a 2,3-sigmatropic rearrangement. [3]