An unexpected change in reaction mechanism in the homo‐Diels‐Alder cycloadditions of <i>N</i>‐methyl‐1,2,4‐triazoline‐3,5‐dione with a series of bicycloalkadienes
作者:Gary W. Breton
DOI:10.1002/poc.4513
日期:2023.8
4-triazoline-3,5-diones (TAD). We investigated the reaction of N-methyl TAD (MeTAD) with the three dienes bicyclo[2.2.1]hepta-2,5-diene (norbornadiene), bicyclo[2.2.2]octa-2,5-diene, and bicyclo[3.2.2]nona-6,8-diene experimentally and computationally. Experimentally, the C7 and C8 dienes resulted in the formation of the expected homo-Diels-Alder product. However, the C9 diene formed a rearranged adduct
已知双环二烯可与有效的亲二烯体(例如N-取代的 1,2,4-三唑啉-3,5-二酮 (TAD))进行均狄尔斯-阿尔德反应。我们研究了N-甲基 TAD (MeTAD) 与三种二烯双环[2.2.1]七-2,5-二烯(降冰片二烯)、双环[2.2.2]辛-2,5-二烯和双环[2.2.2]八-2,5-二烯的反应。3.2.2]nona-6,8-二烯的实验和计算。实验上,C7 和 C8 二烯导致了预期的均狄尔斯-阿尔德产物的形成。然而,C9 二烯形成了重排加合物,这可以通过氮丙啶酰亚胺中间体的中间作用来解释。这些发现得到了计算研究的支持 (ωB97X-D/def2-SVPCH 2 Cl 2}),其中不仅预测了观察到的产物,而且成功定位了导致产物的过渡态。最终,人们确定过渡态结构和能量的细微差异决定了反应的进程。