Regioselective intramolecular Pauson-Khand reactions C60:: An electrochemical study and theoretical underpinning
Regioselective intramolecular Pauson-Khand reactions C60:: An electrochemical study and theoretical underpinning
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DOI：
10.1002/chem.200401200
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发表时间：
2005-04-22
影响因子：
4.3
通讯作者：
Solà, M
中科院分区：
文献类型：
--
作者：
Martín, N;Altable, M;Solà, M
在吡咯烷环（1,6-炔）的C-2位置具有一个或两个异丙基的适当功能化的富勒吡咯烷（1,6-炔）与[CO -2(CO)(8)]有效地和区域选择性地反应，从而产生分别具有三个（5 -d， 7和24）或五个（25）五边形环的Pauson-Khand产物，分别融合到富勒烯球上。具有1,7-,1,9-,1,10-或1,11-烯基的富勒吡咯烷不进行PK反应，相反，与炔基形成的中间二钴配合物在定量产率上被分离出来。用广义梯度近似（GGA）泛函的DFT计算对这些反应性差异进行了研究，发现配位不饱和Co原子与1,6-和1,7-烯中C-60的π体系相互作用形成的中间体存在一些重要的能量和结构差异。不同长度的炔链对所观察到的反应性有影响。循环伏安法表明，环戊烯酮的羰基直接连接到C-60核，导致PK化合物具有显著的电子接受能力。
Suitably functionalized fulleropyrrolidines endowed with one or two propargyl groups at the C-2 position of the pyrrolidine ring (1,6-enynes) react efficiently and regioselectively with [Co-2(CO)(8)] to afford the respective Pauson-Khand products with an unprecedented three (5a-d, 7, and 24) or five (25) pentagonal rings, respectively, fused onto the fullerene sphere. Fulleropyrrolidines with 1,7-, 1,9-, 1,10-, or 1,11-enyne moieties do not undergo the PK reaction and, instead, the inter-mediate dicobalt complexes formed with the alkynyl group are isolated in quantitative yields. These differences in reactivity have been studied by DFT calculations with a generalized gradient approximation (GGA) functional and several important energy and structural differences were found for the intermediates formed by the interaction between the coordinatively unsaturated Co atom and the pi system Of C-60 in 1,6- and 1,7-enynes. The different lengths of the alkyne chains are responsible for the observed reactivities. Cyclic voltammetry reveals that the presence of the cyclopentenone's carbonyl group connected directly to the C-60 core results in PK compounds with remarkable electron-accepting ability.