Studies on the mechanism, selectivity, and synthetic utility of lactone reduction using SmI(2) and H(2)O.
Studies on the mechanism, selectivity, and synthetic utility of lactone reduction using SmI(2) and H(2)O.
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研究使用 SmI(2) 和 H(2)O 还原内酯的机理、选择性和合成效用。
DOI：
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发表时间：
2009
影响因子：
15
通讯作者：
D. Procter
中科院分区：
文献类型：
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作者：
Dixit Parmar;Lorna A. Duffy;Dhandapani V. Sadasivam;H. Matsubara;P. A. Bradley;R. Flowers;D. Procter
虽然简单的脂肪酸酯和内酯一直被认为不在SMI(2)的还原范围内，但通过H(2)O活化稀土试剂，可以以前所未有的方式操纵其中一些底物。例如，与其他类型的内酯和酯相比，SMI(2)-H(2)O还原体系对6元内酯的还原表现出完全的选择性。用停流分光光度法研究了还原动力学。实验和计算研究表明，选择性的来源在于内酯羰基的初始电子转移。SMI(2)-H(2O)O在内酯还原反应中形成的自由基中间体可用于环合反应，得到具有高非对映选择性的环酮(或缩酮)产物。环化反应是第一个酯-烯烃自由基环化反应的例子，其中的酯-烷基相当于酰基自由基。
Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI(2), activation of the lanthanide reagent by H(2)O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI(2)-H(2)O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI(2)-H(2)O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent.