COREY-FUCHs 炔烃合成

重要性，介绍
The one-carbon homologation of aldehydes to the corresponding terminal alkynes using carbon tetrabromide and triphenylphosphine is known as the Corey-Fuchs alkyne synthesis. In 1972, E.J. Corey and P.L. Fuchs examined the synthetic possibility of transforming aldehydes to the corresponding one-carbon chain-extended alkynes. The first step of their procedure involved the conversion of the aldehyde to the corresponding homologated dibromoolefin in two possible ways: I) addition of the aldehyde (1 equivalent) to a mixture of triphenylphosphine (4 equivalents) and carbon tetrabromide (2 equivalents) in CH2Cl2,，at 0 °C in 5 minutes;0℃or II) addition of the aldehyde to a reagent, which is prepared by mixing zinc dust (2 equivalents) with Ph3P (2 equivalents) and CBr4 (2 equivalents) in CH2Cl2 at 23 °C for 24-30h (the reaction time to form the alkyne is 1-2h). Yields are typically 80-90% for this first Wittig-type step. Procedure II,，using zinc dust and less Ph3P,，tends to give higher yields of dibromoolefins and simplifies the isolation procedure In the second step,，the conversion of the prepared dibromoolefins to the corresponding terminal alkynes is accomplished by treatment with 2 equivalents of n-butyllithium at -78 °C (lithium-halogen exchange and elimination), followed by simple hydrolysis. The intermediate is a lithium acetylide，, which can be treated with a number of electrophiles to produce a wide variety of useful derivatives.，a one-pot modified procedure 可以和许多亲电试剂反应生成多种有用的衍生物。

Recently, 关于用四溴化碳和三苯基膦使醛发生一个碳的同系化反应变为相应的末端炔烃的反应就是著名的这个人名反应。

这个年这个人和这个人测试醛转变成相应主链延长一个碳的炔烃反应的可能性。

他们测试过程的第一步包含两种醛转变成相应的二溴烯烃方法：1，醛（1当量）与三苯基膦(4当量)和四溴化碳（2当量）的混合物在二氯甲烷中进行加成反应5分钟反应时间。

2，醛作为一个试剂进行加成反应，将锌粉（2当量）和三苯基膦（2当量）以及四溴化碳（2当量）混合在一起，加入二氯甲烷中，在23℃下反应24-30小时(形成炔烃的反应时间是1-2小时)。

在第一步的wittig反应中产率通常在80-90%。

步骤二：使用锌粉和少量三苯基膦，想要得到较高的二溴烯烃产率并且简化后处理程序. 在第二步，已经制备好的二溴烯烃与两个当量的正丁基锂在零下78摄氏度反应转变成相应的末端炔烃（锂的卤素交换与消除），之后是简单的水解，中间产物是一个炔基锂，最近一个改进的使用叔丁醇钾/ Ph3PCHBr2之后添加过量的证丁基锂的一锅法发表了。

using t-BuOK/(Ph3PCHBr2)Br followed by the addition of excess n-BuLi was
published.5
机理
The mechanism of dibromoolefin formation from the aldehyde is similar to the mechanism of the Wittig reaction.However,，there is very little known about the formation of the alkyne from the dibromoolefin. The mechanism below is one possible pathway to the observed从醛转变成谐二溴代烯烃的反应机理类似于wittig反应的机理。

然而，很少有人知道从谐二溴代烯烃转变成炔烃的反应。

下面的机理有可能是得到的产物的机理。

product.
应用
In the laboratory of J.H. van Boom, 在这个家伙的实验室，the synthesis of highly functionalized cis- and trans-fused polycyclic ethers of various ring sizes via radical
cyclization of carbohydrate-derived β-(alkynyloxy)acrylates was developed.通过碳水化合物自由基环化反应导出β-（炔氧基）丙烯酸酯合成各种环大小的高功能性顺帆异构稠环醚的合成方法得到发展。

7 The radical cyclization precursors were prepared iteratively and the terminal alkyne moieties were installed using the Corey-Fuchsprocedure.自由基环化反应的先驱者反复使用这个方法来制备末端炔烃。

The total synthesis of Galubulimima alkaloid 4,4a-didehydrohimandravine, using an intramolecular Diels-Alder
reaction and a Stille coupling as the key steps, was accomplished in the laboratory of M.S. Sherburn.8 用一个分子内的DA反应和stille耦合反应作为关键步骤合成这个生物碱的全合成反应已经在这个家伙的实验室取得成功The required
vinylstannane intermediate for the Stille coupling was prepared via the one-pot
Corey-Fuchs reaction, followed by
radical hydrostannylation.stille耦合所需要的这个中间体就是用这个反应方法制备的，通过自由基间的锡氢化作用实现的。

W.J. Kerr and co-workers carried out the total synthesis of (+)-taylorione starting from readily available (+)-2-carene
and using a modified Pauson-Khand annulation with ethylene gas as the key step.这个家伙和他的同伴做了一个从高效易得的这个开始并且使用一个改进过的这个环和乙烯气体合成这个的全合成反应The key terminal alkyne
intermediate was prepared by the Corey-Fuchs reaction关键的端位炔烃中间体就是用这
个反应制备的. Interestingly, the ketal protecting group was sensitive to the
excess of CBr4, ，so the addition of this reagent had to be monitored carefully to cleanly transform the aldehyde to the
desired dibromoolefin.有趣的是，这个缩酮保护基团对过量的四溴化碳敏感
所以这个试剂的加入必须严格控制，以使乙醛全部生成需要的二溴烯烃。

W. Oppolzer et al. utilized the Corey-Fuchs alkyne synthesis for the preparation of a key acyclic enynyl carbonate
during the total synthesis of (±)-hirsutene.10这个家伙用这个方法进行一个关键的这个东西的制备。