Ketene Recognizes 1,3-Dienes in Their s-Cis Forms through [4 + 2] (Diels−Alder) and [2 + 2] (Staudinger) Reactions. An Innovation of Ketene Chemistry
作者:Takahisa Machiguchi、Toshio Hasegawa、Akihiro Ishiwata、Shiro Terashima、Shinichi Yamabe、Tsutomu Minato
DOI:10.1021/ja990072u
日期:1999.5.1
The mechanism of ketene−diene reactions has been studied both experimentally and theoretically. Careful experiments of the reactions of diphenylketene (1) with cyclic (s-cis) 1,3-dienes [cyclopentadiene (2) and cyclohexa-1,3-diene (3)] lead to the first direct detection of the Diels−Alder cycloadducts (10 and 11) by low-temperature NMR spectroscopy. The initially formed cycloadducts are converted to
乙烯酮-二烯反应的机理已经在实验和理论上进行了研究。二苯基乙烯酮 (1) 与环状 (s-cis) 1,3-二烯 [环戊二烯 (2) 和环己-1,3-二烯 (3)] 反应的仔细实验导致首次直接检测 Diels-Alder环加合物 (10 和 11) 通过低温 NMR 光谱。最初形成的环加合物通过 [3,3] sigmatropic (Claisen) 重排转化为最终的 Staudinger 产物,环丁酮(6 和 7)。相比之下,乙烯酮 1 与开链 1,3-二烯 [2,3-二甲基-1,3-丁二烯 (4) 和 1-甲氧基-1,3-丁二烯 (5)] 反应,最初提供了两个 Staudinger - 型 (8, 9) 和 Diels-Alder 型环加合物 (12, 13)。Staudinger 环加合物 (8, 9) 最终通过逆克莱森重排转化为 Diels-Alder 产物 (12, 13)。因此,