The alkoxylradical is an important reactive intermediate in mechanistic studies and organic synthesis; however, its current generation fromalcohol oxidation heavily relies on transition metal activation under strong oxidative conditions. Here we report the first visible-light-induced alcohol oxidation to generate alkoxylradicals by cyclic iodine(III) reagent catalysis under mild reaction conditions
Density functional theory (DFT) calculations reveal that the two adjacent iodines in o-diiodoarenes play critical roles in the formation of aryne. The nucleophilic attack of hydride to the electrophilic iodine requires that the adjacent iodine act as a directing group to accelerate this process, whereas mono-substituted iodobenzene lacking the neighboring-group participation makes it difficult. The in-situ-formed
在这里,我们记录了以“旧”邻二碘芳烃作为芳炔祖体的芳炔化学的重新发明。我们建立了 NaH 介导的活化策略,以受控方式生成高反应性芳炔物种。所得芳炔可以有效地参与与未活化酮的C-C σ键插入反应,这是现有方法难以实现的。密度泛函理论 (DFT) 计算表明o中的两个相邻碘-二碘芳烃在芳炔的形成中起关键作用。氢化物对亲电子碘的亲核攻击需要邻近的碘充当导向基团来加速这一过程,而缺乏邻近基团参与的单取代碘苯则使其变得困难。酮原位形成的烯醇化物被建议采用四聚体聚集体与芳烃反应,这解释了具有大取代基的底物的高区域化学性。
Gold-Catalyzed Cycloisomerization of 1,6-Diyne Carbonates and Esters to 2,4a-Dihydro-1<i>H</i>-fluorenes
作者:Weidong Rao、Ming Joo Koh、Dan Li、Hajime Hirao、Philip Wai Hong Chan
DOI:10.1021/ja4032727
日期:2013.5.29
A synthetic method to prepare 2,4a-dihydro-1H-fluorenes efficiently from gold(I)-catalyzed 1,2-acyloxy migration/cyclopropenation/Nazarov cyclization of 1,6-diyne carbonates and esters is described. The suggested reaction pathway provides rare examples of [2,3]-sigmatropic rearrangement in this class of compounds as well as the involvement of an in situ formed cyclopropene intermediate in gold catalysis. Experimental and ONIOM(QM:QM') [our own n-layered integrated molecular orbital and molecular mechanics(quantum mechanics quantum mechanics')] computational studies based on the proposed Au carbenoid species provide insight into this unique selectivity.