双语化学辞典Chem Lexicon
反应 · 有机化学 · 烯烃合成 Organic chemistry · Alkene synthesis

维蒂希反应Wittig reaction

拼音Pinyin wéi dì xī fǎn yìng　别名Also 魏悌希反应；维蒂希烯化； Wittig olefination

定义Definition

维蒂希反应是磷叶立德（Ph₃P=CHR）与醛或酮反应，把 C=O 变为 C=C，生成烯烃和三苯基氧膦的反应。它能在确定位置引入双键。

The Wittig reaction converts the C=O of an aldehyde or ketone into a C=C by reaction with a phosphorus ylide (Ph₃P=CHR), giving an alkene and triphenylphosphine oxide; it places the double bond exactly where the carbonyl was.

机理与立体选择性Mechanism and stereoselectivity

三苯基膦与卤代烷生成𬭸盐，强碱夺去 α-H 得叶立德。叶立德与羰基经 [2+2] 生成氧磷杂环丁烷，再逆 [2+2] 分解为烯烃和 Ph₃P=O（强 P=O 键为驱动力）。非稳定化叶立德（R = 烷基）主要给出 Z-烯烃；稳定化叶立德（R = 酯基、酰基）主要给出 E-烯烃。

Triphenylphosphine and an alkyl halide give a phosphonium salt, which a strong base deprotonates to the ylide. The ylide and carbonyl form an oxaphosphetane by [2+2], which collapses to the alkene and Ph₃P=O (driven by the strong P=O bond). Unstabilised ylides (alkyl R) give mainly Z-alkenes; stabilised ylides (ester, acyl) give mainly E-alkenes.

由来Origin

德国化学家格奥尔格·维蒂希于 1954 年报道，1979 年与 H. C. 布朗共获诺贝尔化学奖。

Reported by the German chemist Georg Wittig in 1954; he shared the 1979 Nobel Prize in Chemistry with H. C. Brown.

应用与变体Uses and variants

工业上用于合成维生素 A（巴斯夫）和类胡萝卜素。施洛瑟改进法可得 E-烯烃；霍纳–沃兹沃思–埃蒙斯反应用膦酸酯负离子，副产物水溶、易除去。缺点是三苯基氧膦难分离、原子经济性差。

Industrially used for vitamin A (BASF) and carotenoids. The Schlosser modification gives E-alkenes; the Horner–Wadsworth–Emmons variant uses phosphonate anions with water-soluble by-products. Drawbacks: Ph₃PO removal and poor atom economy.

反应Reactions

Ph3P=CHR + R′2C=O ⟶ R′2C=CHR + Ph3P=O

𬭸盐 + n-BuLi、NaH 或 KOtBu，THF，−78 °C 至室温，再加入羰基化合物

Phosphonium salt + n-BuLi, NaH or KOtBu in THF at −78 °C to room temperature, then the carbonyl compound

  1. PPh₃ 与卤代烷 SN2 生成𬭸盐。

    PPh₃ and the halide form the phosphonium salt by SN2.

  2. 强碱去质子化得磷叶立德。

    Strong base gives the ylide.

  3. 叶立德与羰基生成氧磷杂环丁烷。

    Ylide and carbonyl form the oxaphosphetane.

  4. 环分解为烯烃和三苯基氧膦。

    It fragments to alkene and Ph₃PO.

Ph3P=CH2 + 环己酮 ⟶ 亚甲基环己烷 + Ph3POPh3P=CH2 + Cyclohexanone ⟶ Cyclohexane + Ph3PO

亚甲基化。

Methylenation.

反应机理图Mechanism

红色弯箭头表示一对电子的移动方向：从电子来源（孤对电子或化学键）指向电子去向。Red curly arrows show where an electron pair moves: from its source (lone pair or bond) to its destination.

1

叶立德碳进攻羰基碳

The ylide carbon attacks the carbonyl carbon

2

四元环氧杂磷杂环丁烷，逆 [2+2] 分解

The four-membered oxaphosphetane breaks apart (retro-[2+2])

3

烯烃 + 三苯基氧膦（强 P=O 键是驱动力）

Alkene + Ph₃P=O (the strong P=O bond drives it)

年表Timeline

  • 1954

    维蒂希报道该反应

    Wittig reports the reaction

  • 1958

    霍纳报道膦酸酯变体

    Horner reports the phosphonate variant

  • 1979

    维蒂希获诺贝尔化学奖

    Wittig receives the Nobel Prize