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The main limitation of the traditional Wittig reaction is that the reaction proceeds mainly via the erythro betaine intermediate, which leads to the Z-alkene. The erythro betaine can be converted to the threo betaine using phenyllithium at low temperature. [18] This modification affords the E-alkene. The Schlosser variant of the Wittig reaction
Modified Wittig–Claisen tandem reaction is a cascade reaction that combines the Wittig reaction and Claisen rearrangement together. The Wittig reaction generates the allyl vinyl ether intermediate that further participates in a Claisen rearrangement to generate the final γ,δ-unsaturated ketone or aldehyde product (Figure "Modified Wittig ...
Wittig reagents are usually described as a combination of two resonance structures: Ph 3 P + CR 2 − ↔ Ph 3 P=CR 2 The former is called the ylide form and the latter is called the phosphorane form, which is the more familiar representation.
In order to obtain the E-alkene, the Schlosser modification of the Wittig reaction can be performed." That agrees with the general description in the "Classical mechanism" section, which accompanies the mechanism leading to 7 (a Z form).
Schlosser modification; Schlosser variant; Schmidlin ketene synthesis; Schmidt degradation; Schmidt reaction; Scholl reaction; Schorigin Shorygin reaction, Shorygin reaction, Wanklyn reaction; Schotten–Baumann reaction; Seliwanoff's test; Semidine rearrangement; Semmler–Wolff reaction; Seyferth–Gilbert homologation; Shapiro reaction
A 1,2-Wittig rearrangement is a categorization of chemical reactions in organic chemistry, and consists of a 1,2-rearrangement of an ether with an alkyllithium compound. [1] The reaction is named for Nobel Prize winning chemist Georg Wittig. [2] [3] The intermediate is an alkoxy lithium salt, and the final product an alcohol.
It is the parent member of the phosphorus ylides, popularly known as Wittig reagents. It is a highly polar, highly basic species. It is a highly polar, highly basic species. Preparation and use
An example of the aza-Wittig-reaction being utilized in organic synthesis is the synthesis of (–)-benzomalvin A. Two intramolecular aza-Wittig-reactions were used to construct the seven-membered ring and the six-membered ring in the molecule's skeleton. [1] Synthesis of (−)-Benzomalvin A via multiple aza-Wittig-reactions