【作者】 周鹏；

【导师】 江焕峰；

【作者基本信息】 华南理工大学 ， 应用化学， 2011， 博士

【摘要】 零价钯启动的炔烃双官能团化已经得到了化学家的广泛的研究,并成功的应用于许多复杂的有机分子的合成。然而,此类方法通常需要特殊的原料和配体,并伴随有一分子或多分子副产物的产生。基于绿色化学的立场,我们发展了几例钯/氧气体系中碳-碳三键的双官能团化反应:第一部分:钯催化氧气氧化两分子烯与一分子炔的交叉偶联。以PdCl₂为催化剂,由贫电子炔烃与烯烃出发,在钯/氧气体系中,我们成功的实现了炔烃与烯烃的高选择性交叉三聚;通过控制条件及改变反应底物,我们可以高选择性的实现炔烃与烯烃的1:2交叉三聚为1,3,5-三烯或者1,2,4,5-四取代苯衍生物。此外,通过一些控制试验,本文也对其机理进行了简单的探索,我们推测这两个反应是氯钯化启动的,然后在与两分子炔烃发生Heck串联反应。在上述两个过程中,所需的氧化剂仅为最绿色的氧气,而副产物仅为水。该方法为首例钯催化的炔/烯（1/2）的交叉杂三聚反应。第二部分:乙酰氧钯化启动的炔烯偶联。乙酰氧钯化可以比较便捷的实现炔烃的双官能团化,并一步构筑C-O键与C-C键。然而,在这些方法中,基于β-氢消除而保持烯烃碳-碳双键的未有报道。我们在Pd（OAc）₂催化下,O₂与Cu（OAc）₂作为共氧化剂,KBr与K₂CO₃为添加剂,在HOAc/CH₃CN中实现了炔烃尤其是富电子炔烃的乙酰氧钯化,并用末端烯烃捕捉C-Pd键,进而β-H消除高选择性得到了一系列的1-乙酰氧基-1,3-二烯。该方法对于末端烯的适用范围较广。同时,我们发现2-甲基丙烯酸甲酯也在这个反应中表现出不俗的活性,并得到了乙酰氧基取代的1,4-二烯,而非常见的1,3-二烯。第三部分:氯钯化启动的[2+2+2]环化反应。我们从1,6-二炔与丙烯酸酯出发,在PdCl₂催化下,以CuCl₂·2H2O与O₂为氧化剂,实现了两者的环化反应,且得到了一系列的苯并五元环。此外,我们成功的分离了中间产物,并通过控制试验对该反应的机理进行了初步的研究。基于中间产物与控制试验,我们认为这是一个氯钯化启动的[2+2+2]氧化环化反应。更多还原

【Abstract】 Pd（0）-catalyzed processes is now recognized to be a useful tool for constructing complex organic compounds which has undergone great development during the past decades. However, special ligands and restricted starting materials usually are needed for respectful yields of the desired products and one or more molecular byproducts usually were losted during these transformations. Combining various factors of green chemistry with Pd-catalyzed coupling reactions, we developed several example of difunctionalization of alkynes in the system of Pd/O₂:1) Highly chemoselective palladium-catalyzed cross-trimerization between alkyne and alkenes leading to 1,3,5-trienes or 1,2,4,5-tetrasubstituted benzenes with dioxygen: A palladium-catalyzed 1:2 linear/cyclic cross-trimerization of alkyne with alkenes using molecular oxygen as the sole oxidant has been reported for the first time. Through changing the starting alkynes or additives, a series of 1,3,5-trienes or 1,2,4,5-tetrasubstituted benzenes are obtained with high chemoselectivity respectively and mechanisms of these reactions are proposed based on some controlled examination. In both transformations, water is the sole byproduct.2) Acetoxypalladation of unactivated alkynes and capture with alkenes to give 1-acetoxy-1,3-dienes taking dioxygen as terminal oxidant: A new and general protocol for the synthesis of 1-acetoxy-1,3-dienes by an acetoxypalladation/Heck cross-coupling/β-H elimination tandem process is described in which dioxygen is the terminal oxidant. Electron-rich and electron-deficient alkynes are both effective substrates in this system. Interesting, almost all the terminal alkenes including methyl methacrylate which is usually inert in other Heck cross-coupling are effective for the reaction. It is the first example of acetoxypalladation of diarylalkynes.3) An aerobic [2+2+2] cyclization via chloropalladation: From 1,6-diynes and acrylates to substituted aromatic carbocycles: A Pd-catalyzed aerobic [2+2+2] cyclization of 1,6-diynes and acrylates proceeding through chloropalladation process has been developed. Poly-substituted five-membered aromatic carbocycles/heterocycles were obtained in good to excellent yields. The key most absorbing point is the detection of intermediate C had been successfully isolated and characterized, and which is the first mechanistic evidence in [2+2+2] cyclization reactions via chloropalladation process. Results of mechanistic study are consistent with the proposed reaction mechanism.更多还原