A comparison of secondary and tertiary amides as directors of ortho and adjacent benzylic lithiation and of asymmetric induction in ortho lithiated benzamides
作者:Peter Beak、Anthony Tse、Joel Haawkins、Chin-Wen Chen、Sander Mills
DOI:10.1016/s0040-4020(01)91916-7
日期:1983.1
Comparisons are made between the influence of secondary and tertiary amides on ortho and adjacent benzylic metallations of benzamides. In the intramolecular competition offered by N,N-diethyl-N-ethylterephthalamide (1) the tertiary amide is the more effective director of ortho lithiation, while the secondary amide is better in the intermolecular competitions offered by the pairs N-ethyl-(9): N,N-diethylbenzamide(10)
比较仲酰胺和叔酰胺对苯甲酰胺的邻位和邻位苄基金属化的影响。在N,N-二乙基-N-乙基对苯二甲酰胺(1)提供的分子内竞争中,叔酰胺是邻位锂化的更有效导向器,而仲酰胺在N-乙基-(9 ):N,N-二乙基苯甲酰胺(10)和N-异丙基-(11):N,N-二异丙基苯甲酰胺(12)。在2-异丙基苯甲酰胺25和26中,仲酰胺和叔酰胺都可以直接金属化到酰胺上; 然而,在仲2-乙基和2-甲基苯甲酰胺中发现苄基金属化21和22以及叔2-乙基苯甲酰胺19。注意到19的抗-N-亚甲基的磁性不等价。内硫基(S)-O-甲基-N-苯甲酰亮氨醇(34)与1-萘甲醛-1-d的反应在内酯化后得到3-(1-萘-1-d)-邻苯二甲酸酯与10%对映异构体过量的。通过在环化之前分离非对映异构体,可以以高对映体纯度获得邻苯二甲酰亚胺。对照实验确定观察到的不对称诱导归因于非对映异构过渡态。相应的叔苯甲酰胺在诱导不对称方面无效。为这些观察提供了结构和机械原理。