Highly Efficient Bond-Forming Reactions utilizing Ynolates

我们发现烯醇化物与酮反应生成β-内酯烯醇化物，其开环形成四取代烯烃。本课题主要研究了炔醇类化合物的烯化反应，包括烯化反应的范围和局限性。1）芳基烷基酮、芳基芳基酮和烷基烷基酮的烯化反应：芳基烷基酮的烯化反应具有E-选择性。在芳基芳基酮的情况下，富电子芳基优选被定位为羧基的反式。2）酰基硅烷的烯烃化反应：具有理想的Z-选择性。该烯化反应得到乙烯基硅烷是第一个成功的高效烯化反应，得到具有高通用性的四取代烯烃。产物容易转化为其他四取代烯烃。例如，Hiyama将乙烯基硅烷与芳基碘偶联成功地提供了偶联产物而不添加氟化物。贝考斯 ...更多信息 通过羰基氧的配位形成高价硅烷，Si-C键被活化。3）酯的烯化反应：由于酯羰基化合物的亲电性较差，用Wittig试剂等常规试剂进行酯羰基化合物的烯化反应比较困难。烯醇化物容易与酯反应生成烯化产物（烯醇醚），产率高，E-选择性高，E/Z选择性由β-内酯烯醇化物开环（电环化反应）的torquosectionality决定。过渡态中的2^<nd>轨道相互作用决定了选择性。理论计算揭示了几种轨道相互作用：芳基的π轨道和C-H键的σ轨道稳定过渡态中断开的C-O轨道的σ^* 轨道，使其向外旋转; C-Si、C-O和C-C键的σ^* 轨道稳定断开的C-O键的σ轨道，使其向内旋转。少

We have found that ynolates react with ketones to afford β-lactone enolates, which are ring-opened to form tetrasubstituted olefins. In this research project, we investigated the details of the olefinations via ynolates including scope and limitations.1)Olefination of aryl alkyl ketones, aryl aryl ketones, and alkyl alkyl ketones : the olefination of aryl alkyl ketones gave the products with E-selectivity. In the case of aryl aryl ketones, the electron-rich aryl groups preferred to be positioned to be trans to carboxyl groups. Pinacolon furnished the olefin with Z-selectivity.2)Olefination of acylsilanes : Perfect Z-selectivity was achieved. This olefination giving vinylsilanes is the first successful efficient olefination giving tetrasubstituted olefins with high generality. The products are easily converted into other tetrasubstituted olefins. For examples, Hiyama coupling of the vinylsilanes with aryl iodide successfully provided the coupling products without adding fluoride. Becaus … More e of formation of hypervalent silanes by coordination of carbonyl oxygen, the Si-C bond is activated. Taking advantage the activation, novel synthesis of silalactones via electrophilic cleavage of C-Si bonds was found.3)Olefination of esters : it has been difficult in olefination of ester carbonyls by conventional reagents like Wittig reagents, due to the poor electrophlicity of the carbonyls. Ynolates easily react with esters to give the olefinated products (enol ethers) in good yield with high E-selectivity.The E/Z selectivity is determined by torquoselectivity in ring-opening (electrocyclic reactions) of the β-lactone enolates. The torquoselectivity is governed by 2^<nd> orbital interactions in the transition states. Theoretical calculations disclosed several orbital interactions : π-Orbitals of aryl groups and σ-orbitals of C-H bonds stabilize the σ^* orbital of the disconnecting C-O orbital in the transition states to make them rotate outward, σ^* Orbitals of C-Si, C-O, and C-C bonds stabilize the σ orbital of the disconnecting C-O bond to make them rotate inward. Less