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The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. [1] [2] [3] Most often, the Wittig reaction is used to introduce a methylene group using ...
An example of modest stereoselectivity is the dehydrohalogenation of 2-iodobutane which yields 60% trans-2-butene and 20% cis-2-butene. [5] Since alkene geometric isomers are also classified as diastereomers, this reaction would also be called diastereoselective.
The [2,3]-Wittig rearrangement is the transformation of an allylic ether into a homoallylic alcohol via a concerted, pericyclic process.Because the reaction is concerted, it exhibits a high degree of stereocontrol, and can be employed early in a synthetic route to establish stereochemistry.
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The Horner–Wadsworth–Emmons (HWE) reaction is a chemical reaction used in organic chemistry of stabilized phosphonate carbanions with aldehydes (or ketones) to produce predominantly E-alkenes. [1] The Horner–Wadsworth–Emmons reaction. In 1958, Leopold Horner published a modified Wittig reaction using phosphonate-stabilized carbanions.
Ulrich Schöllkopf (11 October 1927 – 6 November 1998) was a German chemist and together with Georg Wittig discovered the Wittig reaction in 1956. Later in 1981 he published the synthesis method for amino acids known as the Bislactimether method or Schöllkopf method.
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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.