An Innovation in Ketene Chemistry

烯酮化学的创新

• 批准号: 10640510
• 负责人: MACHIGUCHI Takahisa
• 金额: $ 2.43万
• 依托单位: Saitama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640510/
• 关键词: non-recognition; 1,3-dienes; ketene; [2 + 2] cycloaddition; [4 + 2] cycloaddition; C=O bond; α-methylenedihydropyran; cyclobutanone; ジエン; シクロプタノン; 分子軌道理論; 共役; 不飽和; 素過程; 区別

Non-Recognition for 1,3-dienes in ketene reactions has long been an important problem in organic chemistry. We have solved the problem in this research. The mechanism of ketene-diene cycloadditions has been studied both theoretically and experimentally. The paths of the cycloadditions of diphenylketene to cyclic and linear dienes are traced by precise experiments and ab initio calculations. The obtained results show that the addition paths and final products depend upon the structures of dienes, cyclic (with s-cisform) or linear (with s-cis and s-trans forms). The cycloadditions of diphenylketene to cyclic dienes are two-step processes, composed of [4 + 2] addition and Clasien rearrangement, leading to [2 + 2] cycloadducts. On the other hand, those of diphenylketene to linear dienes are two-step processes, composed of [2 + 2] addition and retro-Claisen rearrangement, [4 + 2] cycloadducts.Careful experiments in the reactions of diphenylketene with cyclic (s-cis) 1,3-dienes lead to the f … More irst detection of the Diels-Alder cycloadducts (α-methylenedihydropyrans) by low-temperature NMR spectroscopy. The initially formed cycloadducts are converted by the final [2 + 2]-type products, cyclobutanones, by a [3,3] sigmatropic (Claisen) rearrangement. In contrast, the ketene reacts with open-chain 1,3-dienes (with s-cis and s-trans forms) to form initially both the [2 + 2]-type and [4 + 2]-type cycloadducts. The formers are converted to [4 + 2]-type cycloadducts by retro-Clasien rearrangement. Thus, ketene distinguishes s-cis 1,3-dienes from s-trans ones leading to the initially formed [4 + 2] and [2 + 2] cycloadducts, respectively. The [2 + 2] cycloadduct is converted to the final [4 + 2] product through retro-Claisen rearrangement. Those experimental results are consistent with theoretical ones perfectly. We discovered that ketene is a dienophile not well-known [2 + 2] cycloaddition but for [4 + 2] (Diels-Alder) reactions across its C=O bond. Thus, we have made an innovation in ketene chemistry. Less

乙烯酮反应中1,3-二烯的不可识别长期以来一直是有机化学中的一个重要问题。我们在这项研究中解决了这个问题。乙烯酮-二烯环加成反应机理已从理论和实验两个方面进行了研究。通过精确的实验和从头算计算，追踪了二苯基乙烯酮与环状和直链二烯的环加成路径。所得结果表明，加成路径和最终产物取决于二烯的结构，环状（s-顺式）或线性（s-顺式和s-反式）。二苯基乙烯酮与环状二烯的环加成是两步过程，由[4 + 2]加成和Clasien重排组成，形成[2 + 2]环加合物。另一方面，二苯基乙烯酮转化为线性二烯是两步过程，由[2 + 2]加成和逆克莱森重排组成，[4 + 2]环加合物。对二苯基乙烯酮与环状（顺式）1,3-二烯反应的仔细实验导致首次检测到狄尔斯-阿尔德环加合物。 （α-亚甲基二氢吡喃）通过低温核磁共振波谱分析。最初形成的环加合物通过[3,3] σ（克莱森）重排被最终的[2 + 2]型产物环丁酮转化。相反，乙烯酮与开链 1,3-二烯（具有 s-顺式和 s-反式形式）反应，最初形成 [2 + 2] 型和 [4 + 2] 型环加合物。前者通过逆克拉西重排转化为[4 + 2]型环加合物。因此，乙烯酮将 s-顺式 1,3-二烯与 s-反式 1,3-二烯区分开来，分别形成最初形成的 [4 + 2] 和 [2 + 2] 环加合物。 [2 + 2]环加合物通过逆克莱森重排转化为最终的[4 + 2]产物。这些实验结果与理论结果完全一致。我们发现乙烯酮是一种亲双烯体，不是众所周知的 [2 + 2] 环加成反应，而是在其 C=O 键上进行 [4 + 2] (Diels-Alder) 反应。因此，我们在乙烯酮化学方面做出了创新。较少的

项目成果

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