stereoselectivity of the cyclizations depends on relative stability of the cyclization-generated radicals. Therefore, the oxidative free-radical cyclization of allyl alpha-methyl-beta-ketoester 5a with Mn(OAc)(3) gives a cis product as a major product, while the same oxidative free-radical cyclizations of substituted allyl alpha-methyl-beta-ketoesters 5b and 5c with Mn(OAc)(3) produce trans products as major
通过DFT方法在UB3LYP / 6-31G
水平上研究了取代的烯丙基α-甲基-β-
酮酸酯基11、14和18的环化;结果表明,顺式环化比相应的反式环化更容易,但是环化后产生的顺式自由基不一定比相应的顺式环化更稳定。在
乙酸或
乙腈中存在Mn(OAc)(3)的情况下,11、14和18的自由基环化都是可逆的,并在热力学控制下进行,环化的立体选择性取决于环化的相对稳定性-产生自由基。因此,烯丙基α-甲基-β-
酮酸酯5a与Mn(OAc)(3)的氧化自由基环化反应将顺式产物作为主要产物,