Origins of Large Rate Enhancements in the Nazarov Cyclization Catalyzed by Supramolecular Encapsulation
作者:Courtney J. Hastings、Robert G. Bergman、Kenneth N. Raymond
DOI:10.1002/chem.201303885
日期:2014.4.1
irreversible electrocyclization. Although electrocyclization is rate determining in the uncatalyzed reaction, the barrier for water loss and for electrocyclization are nearly equal in the assembly‐catalyzed reaction. Analysis of the energetics of the catalyzed and uncatalyzed reaction revealed that transition‐state stabilization contributes significantly to the dramatically enhanced rate of the catalyzed
自组装的超分子主体[Ga 4 L 6 ] 12−(1 ; L = N,N‐双(2,3-‐二羟基苯甲酰基)‐1,5‐二氨基萘)催化Nazarov环化1,3-戊二烯醇的过程高效率。催化反应的进行速度比背景反应快一百万倍,与某些酶体系中观察到的增加相当。进行了详细的研究以阐明戊二烯醇的催化的和未催化的纳扎罗夫环化的反应机理。动力学分析和18O交换实验暗示了一种机制,其中包封,质子化和从基质中流失的水分是可逆的,然后进行不可逆的电环化。尽管在未催化反应中电环化是决定速率的,但在组装催化反应中水损失和电环化的障碍几乎相等。对催化和未催化反应的能量学分析表明,过渡态稳定化显着促进了催化反应速率的显着提高。