Alkali-metal-mediated manganation: A method for directly attaching manganese(II) centers to aromatic frameworks
Alkali-metal-mediated manganation: A method for directly attaching manganese(II) centers to aromatic frameworks
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DOI：
10.1002/anie.200604542
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Mulvey, Robert E.
中科院分区：
文献类型：
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作者：
Garcia-Alvarez, Joaquin;Kennedy, Alan R.;Mulvey, Robert E.
芳香族化合物的金属化(金属-氢交换)反应是合成化学中的一种重要方法，通常属于高活性的有机金属领域，如烷基锂化合物、LICKOR(烷基锂化合物与叔丁醇钾共络合)超碱或锂酰胺。严格地说，这些反应是锂(或钾化)反应，因为进入的锂原子(或钾原子)取代了离开的氢原子。低极性金属镁、锌和铝通常形成反应缓慢的金属化试剂，对芳香族化合物无效。因此，要将这些活性较低的金属直接连接到芳香族支架上，必须事先合成锂化芳香族化合物，然后必须进行额外的复分解反应，通常涉及金属卤化物(例如，RMgX、ZnX2或R2AlX)。离子卤化物的存在往往限制了可用于与碳氢化合物和芳烃反应的溶剂的范围，这通常被排除在有利于极性替代物(通常是乙醚或四氢呋喃)的范围内。然而，最近有研究表明，将锂(或另一种碱金属)与这些劣质多价金属中的一种在同一有机金属分子(‘-ate’配方)中配对，可以产生能够直接磁化、[2，3]镀锌、[3]或[4]铝化[4]芳香族底物的“协同”混合金属试剂，从而避免了后续复分解的需要。除了这种新的无机(金属)观点，这些协同试剂还可以通过促进不寻常的区域选择性去质子化(例如，在甲苯[5]和N，N，N二甲基苯胺[6]的情况下是间位的)或特殊的多去质子化(例如，在二茂铁[7]的情况下是2，6-两倍，在二茂铁及其8族同系物的情况下是1，1‘，3，3’-四倍)，开辟新的有机领域。
A keystone methodology in synthetic chemistry, metalation (metal-hydrogen exchange) reactions of aromatic compounds are usually the domain of highly reactive polar organometallics such as alkyllithium compounds, LICKOR (alkyllithium compounds cocomplexed with potassium tertbutoxide) superbases, or lithium amides.[1] Strictly these reactions are lithiations (or potassiations) as the incoming lithium atom (or potassium atom) takes the place of the outgoing hydrogen atom. The lower-polarity metals magnesium, zinc, and aluminum generally form slow-reacting metalating agents which are ineffective towards aromatic compounds. Therefore, to attach these less reactive metals directly to an aromatic scaffold, the lithiated aromatic compound must be synthesized beforehand and then an additional metathetical reaction often involving a metal halide (for example, RMgX, ZnX2, or R2AlX) has to be carried out. The presence of the ionic halide often limits the range of solvents available for such reactions with hydrocarbons and arenes, which are generally ruled out in favor of polar substitutes (commonly ether or THF). Recently, however, it has been shown that pairing lithium (or another alkali metal) with one of these inferior multivalent metals in the same organometallic molecule (an'-ate'formulation), can generate'synergic', mixed-metal reagents capable of directly magnesiating,[2, 3] zincating,[3] or aluminating [4] aromatic substrates, thus circumventing the need for a subsequent metathesis. In addition to this new inorganic (metal) perspective, these synergic reagents can open up new organic horizons by promoting unusual regioselective deprotonations (for example, meta-orientated in the cases of toluene [5] and N, Ndimethylaniline [6]) or special polydeprotonations (for example, 2, 6-twofold in the case of naphthalene [7] and 1, 1', 3, 3'-fourfold in the cases of ferrocene and its Group 8 homologues [8]).