Torquoselectivity in the Cationic Cyclopentannelation of (2Z)-Hexa-2,4,5-trienal Acetals
作者:Beatriz Iglesias、Angel R. de Lera、Jesús Rodríguez-Otero、Susana López
DOI:10.1002/1521-3765(20001103)6:21<4021::aid-chem4021>3.3.co;2-e
日期:2000.11.3
calculations for model systems are consistent with the acid-catalyzed rearrangement of 2-[(1Z)-hexa-1,3,4-trienyl]dioxolanes 1 to tetrahydroalkylidenecyclopenta-1,4-dioxins 4; this involves the electrocyclic ring closure of substituted hydroxypentadienyl carbocations. The reaction, which may be considered a variant of the Nazarov cyclization, occurs much more readily than the standard Nazarov cyclization, proceeding
模型系统的分子间和分子内捕获实验和密度泛函理论从头计算与2-[((ZZ)-hexa-1,3,4-trienyl] dioxolanes 1酸催化的重排成四氢烷基亚基环戊-1,4一致-二恶英4; 这涉及取代的羟基戊二烯基碳阳离子的电环闭合。该反应可能被视为纳扎罗夫环化反应的一种变体,比标准纳扎罗夫环化反应更容易发生,甚至在-30摄氏度下仍能快速进行。B3LYP / 6-31G ** // HF / 6-31G **计算对于模型36、38和40的预测,在环化末端的两个交替的扭转分别与活化能相差0.55、0.56和1.60 kcalmol(-1),有利于R向外旋转。