定义Definition
珀金反应是芳香醛与脂肪酸酐在相应羧酸盐（碱）存在下加热缩合，生成 α,β-不饱和芳香酸（如肉桂酸）的反应。
The Perkin reaction is the condensation of an aromatic aldehyde with an aliphatic acid anhydride, heated with the alkali salt of the corresponding acid as base, to give an α,β-unsaturated aromatic acid such as cinnamic acid.
机理Mechanism
乙酸根作碱夺取乙酸酐的 α-H，生成烯醇负离子，对醛羰基发生羟醛型加成；所得醇盐发生分子内酰基转移，再经消除（失去乙酸）生成不饱和酸酐，水解得到肉桂酸。
Acetate removes an α-H from acetic anhydride; the enolate adds to the aldehyde (aldol-type); the alkoxide undergoes intramolecular acyl transfer, elimination of acetic acid gives an unsaturated anhydride, and hydrolysis yields cinnamic acid.
由来Origin
英国化学家威廉·亨利·珀金（第一个合成染料苯胺紫的发现者）于 1868 年报道，并用此法合成了香豆素。
Reported in 1868 by William Henry Perkin — discoverer of the first synthetic dye, mauveine — who also used it to make coumarin.
特点Features
需要高温（约 180 °C）、较长时间；主要得到 E 型（反式）肉桂酸。以水杨醛为原料时生成的邻羟基肉桂酸内酯化得到香豆素。现代多用克诺文纳格尔缩合或赫克反应制备肉桂酸衍生物。
It needs high temperature (~180 °C) and long times and gives mainly (E)-cinnamic acids. From salicylaldehyde the o-hydroxycinnamic acid lactonises to coumarin. Today Knoevenagel condensation or the Heck reaction are often preferred.
反应Reactions
无水乙酸钠或乙酸钾，约 180 °C 加热数小时
Anhydrous sodium or potassium acetate, about 180 °C for several hours
乙酸根夺取酸酐 α-H 生成烯醇负离子。
Acetate deprotonates the anhydride at the α-carbon.
烯醇负离子加成到醛羰基。
The enolate adds to the aldehyde.
酰基转移与消除生成不饱和酸酐。
Acyl transfer and elimination give the unsaturated anhydride.
水解得到 α,β-不饱和酸。
Hydrolysis gives the α,β-unsaturated acid.
合成肉桂酸。
Synthesis of cinnamic acid.
年表Timeline
- 1856
珀金发现苯胺紫
Perkin discovers mauveine
- 1868
珀金报道该缩合并合成香豆素
Perkin reports the condensation and synthesises coumarin