N-sulfinylcarboximidates as a new class of chiral bidentate ligands: application to asymmetric coordination chemistry.
N-sulfinylcarboximidates as a new class of chiral bidentate ligands: application to asymmetric coordination chemistry.
复制标题
N-亚磺酰亚胺酯作为一类新型手性二齿配体：在不对称配位化学中的应用。
作者：
Zhijie Lin;M. A. Çeli̇k;Chen Fu;K. Harms;G. Frenking;E. Meggers
在Alfred Werner首次实验证实八面体金属配合物具有金属中心手性的一百年后，八面体配合物的不对称合成仍然是一个艰巨的挑战。众所周知，精心定制的配位体中的手性有机基团能够在金属络合物形成期间有效地控制金属络合物的绝对构型，从而将碳中心手性转移到八面体金属中心。然而，考虑到不对称配位化学范围的扩大，当前的一个挑战在于开发可以经济地合成的手性配体，同时能够有效地控制金属中心构型，并且可以在不损害诱导的金属中心立体化学的情况下随后被去除，从而充当瞬时手性助剂。在这里，我们希望介绍一个新的，但令人惊讶的简单的手性双齿配体，并报告其应用的手性辅助介导的不对称合成的八面体钌多吡啶配合物。我们最近关于手性钌配合物的不对称合成的研究使我们认识到含亚砜螯合配体的优点，因为它们具有可以直接与金属配位的立体中心，从而允许特别容易地控制金属中心构型（方案1a）。然而，以前使用的手性2-亚磺酰基苯酚是繁琐的，以高度对映体纯的方式合成，因此具有有限的实用价值。寻求容易获得的，atomeconomic手性亚砜助剂，我们设想，方案1 B中所示的N-乙酰基亚磺酰胺可能是一个特别有趣的候选人，通过可逆地协调作为一个双齿配体通过其去质子化的N-亚磺酰基甲酰亚胺形式。方便地，（R）-N-乙酰基-叔丁烷亚磺酰胺（（R）-阿萨;方案1 B）可以通过将市售的对映体纯的叔丁烷亚磺酰胺（Ellman亚磺酰胺）乙酰化而在单一步骤中合成，所述对映体纯的叔丁烷亚磺酰胺是在有机合成中作为涉及羰基的不对称转化的手性助剂而被充分确立的化合物。我们通过在K2 CO 3存在下使（R）ASA与外消旋cis-[Ru ACHTUNGTRENNUNG（bpy）2Cl 2]反应来测试其与（R）阿萨的不对称配位化学（0.5当量）在乙二醇中在170 ℃下反应90秒，这类似于最近开发的用于手性亚磺酰基苯酚助剂的程序，令人高兴的是，我们以77%的产率获得了作为单一非对映异构体的L-（S）-1（方案2）。显然，由于从50：50的D-构型的顺式-[Ru ACHTUNGTRENNUNG（bpy）2Cl 2]的混合物开始，大量的D-构型的钌起始材料必须已经转化其金属中心构型
One hundred years after Alfred Werner s first experimental verification of metal-centered chirality in octahedral metal complexes, the asymmetric synthesis of octahedral coordination compounds still remains a formidable challenge. It is well established that chiral organic groups within carefully tailored coordinating ligands are capable of effectively controlling the absolute configuration of metal complexes during their formation, thereby transferring carbon-centered chirality to octahedral metal centers. However, having in mind an expansion of the scope of asymmetric coordination chemistry, one current challenge lies in the development of chiral ligands that can be synthesized economically, are at the same time capable of efficiently ruling the metal-centered configuration, and can be removed afterwards without compromising the induced metal-centered stereochemistry, thus serving as transient chiral auxiliaries. Here, we wish to introduce a new but surprisingly simple chiral bidentate ligand and report its application to the chiral-auxiliary-mediated asymmetric synthesis of octahedral ruthenium polypyridyl complexes. Our recent studies on the asymmetric synthesis of chiral ruthenium complexes made us appreciate the advantages of sulfoxide-containing chelate ligands because they possess a stereogenic center that can directly coordinate to the metal and thus permit an especially facile control of the metal-centered configuration (Scheme 1 a). However, the previously employed chiral 2-sulfinylphenols are cumbersome to synthesize in a highly enantiomerically pure fashion and thus of limited practical value. Seeking readily accessible, atomeconomical chiral sulfoxide auxiliaries, we envisioned that the N-acetylsulfinamide shown in Scheme 1 b might be an especially interesting candidate by coordinating reversibly as a bidentate ligand through its deprotonated N-sulfinylcarboximidate form. Conveniently, (R)-N-acetyl-tert-butanesulfinamide ((R)-ASA ; Scheme 1 b) can be synthesized in a single step by acetylation of commercially available enantiomerically pure tert-butanesulfinamide (Ellman s sulfinamide), a compound that is well established in organic synthesis as a chiral auxiliary for asymmetric transformations involving carbonyl groups. We tested asymmetric coordination chemistry with (R)ASA by reacting it with racemic cis-[Ru ACHTUNGTRENNUNG(bpy)2Cl2] in the presence of K2CO3 (0.5 equiv) in ethylene glycol at 170 8C for 90 seconds, which is analogous to a procedure developed recently for chiral sulfinylphenol auxiliaries, and to our delight we obtained L-(S)-1 as a single diastereomer in a yield of 77 % (Scheme 2). Apparently, since starting from a 50:50 mixture of Land D-configured cis-[Ru ACHTUNGTRENNUNG(bpy)2Cl2], a significant amount of the D-configured ruthenium starting material must have converted its metal-centered configuration
影响因子：
15
作者：
Clayden, Jonathan;Fletcher, Stephen P.;Rowbottom, Stephen J. M.
通讯作者：
Rowbottom, Stephen J. M.