The Wittig Reaction - Chemistry LibreTexts
Organophosphorus ylides react with aldehydes or ketones to give substituted alkenes in a transformation called the Wittig reaction. This reaction is named for George Wittig who was awarded the Nobel prize for this work in 1979.
Wittig Reaction - Examples and Mechanism - Master Organic …
2018年2月6日 · They are usually made through just two familiar reactions: nucleophilic substitution reaction (S N 2) followed by an acid-base reaction. We start by treating an alkyl halide (another functional group “hub” in our airport analogy) with the excellent nucleophile triphenylphosphine (PPh 3 ), which displaces the leaving group (via S N 2) to ...
Wittig reaction - Wikipedia
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.
Wittig Reaction - Organic Chemistry Portal
The Wittig Reaction allows the preparation of an alkene by the reaction of an aldehyde or ketone with the ylide generated from a phosphonium salt. The geometry of the resulting alkene depends on the reactivity of the ylide.
Triphenylphosphine - Wikipedia
In the Appel reaction, a mixture of PPh 3 and CX 4 (X = Cl, Br) is used to convert alcohols to alkyl halides. Triphenylphosphine oxide (OPPh 3) is a byproduct. PPh 3 + CBr 4 + RCH 2 OH → OPPh 3 + RCH 2 Br + HCBr 3. This reaction commences with nucleophilic attack of PPh 3 on CBr 4, an extension of the quaternization reaction listed above.
Phosphonium ylides react with aldehydes to produce oxaphosphetane 1Z or 1E, which decomposes by a syn-cycloreversion process to the alkene. In the formation of Z-alkenes, an early, four-centered transition state is proposed.
20.4. The Wittig reaction | Organic Chemistry II - Lumen Learning
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide (often called a Wittig reagent) to give an alkene and triphenylphosphine oxide. The Wittig reaction was discovered in 1954 by Georg Wittig, for which he was awarded the Nobel Prize in Chemistry in 1979.
有机人名反应——Mitsunobu反应（光延反应） - 知乎专栏
2021年4月5日 · Mitsunobu反应（光延反应）是一种双分子亲核取代反应（SN2反应）。 1967年， Mitsunobu 报导了在三苯膦（PPh3）和偶氮二甲酸二乙酯（DEAD）作用下酸和醇缩合成酯的新方法。 当底物为仲醇的时候，与羟基相连的碳原子的构型会发生翻转。 经过多年的研究和发展，形成了一大类合成方法，称之为Mitsunobu 反应。 这类反应被广泛应用在有机合成，特别是天然产物的合成中。 许多其他的亲核试剂都能代替常规的羧酸来进行反应，但亲核试剂应为酸性，因 …
Wittig Reaction - Chemistry LibreTexts
Phosphonium ylides 1 react with carbonyl compounds 2 via a π²s/π²a [2+2] cycloaddition to directly form the oxaphosphetanes 4a and 4b. The stereochemistry of the product 5 is due to the addition of the ylide 1 to the carbonyl 2 and to the equilibration of the intermediates.
Wittig Reaction - Common Conditions - Common Organic …
The reaction of iminophosphoranes with aldehydes or ketones gives the imine product. The iminophosphoranes are typically formed from the reaction of the corresponding azide (R3-N3) with triphenylphosphine ( PPh3 ).