Asymmetric Reaction Utilizing Planar Chiral Arenes

当芳环被两个不同的基团取代时，(Eta6-芳烃)铬配合物以两种基于平面手性的对映体形式存在。在本研究项目中，我们研究了平面手性(芳烃)铬配合物的不对称合成。首先，通过以下方法制备了具有对映体活性的平面手性(芳烃)铬配合物。在乙酸异丙烯存在下，脂肪酶能以较高的对映体过量将外消旋(欧米微取代苯甲醇)铬(CO)_3络合物拆分成对映体活性铬络合物。用手性锂二胺在对映体邻位上锂化合保护的苯酚或苯胺类化合物，然后用亲电体猝灭得到光学活性的(二取代芳烃)铬配合物。在钯催化剂存在下，(2，6-二取代卤苯)铬与邻位取代苯基硼酸交叉偶联得到…更多的非对映选择性的铬(CO)3配位的联芳基具有互补的轴向手性依赖于芳基硼酸的邻位取代基。Omiron-烷基或Omiron-羟甲基取代苯基硼酸与(芳基卤化物)铬配合物反应，得到邻位取代基与三羰基铬片段同步取向的联芳基。以小分子甲酰基苯基硼酸为原料，立体选择性地合成了非对映异构体的反偶联产物。在热条件下，动力学控制的交叉偶联产物很容易异构化成动力学稳定的单铬(CO)_3络合联芳基。整个过程可以被认为是从单一平面手性(芳烃)铬络合物开始的两个轴向手性联芳基的对映选择性制备。这种利用平面手性芳香铬配合物立体选择性合成轴向手性联芳烃的方法可用于生物活性天然产物(-)-硬脂酮的全合成。对映体纯的(邻位取代苯甲醛)铬(CO)_3络合物用二碘化钐(II)处理得到单一的双三羰基铬络合二苯乙烷1，2-二醇，其构型为三配位，两个相对的立体化学位置受相邻芳环的平面配位性控制。同样地，邻位取代苯乙二胺与二碘化钐形成的对映体纯的三羰基铬络合物在氧化去金属化后得到对映体1，2-二胺。较少

(eta6-Arene) chromium complexes exist in two enantiomeric forms based on planar chirality, when the arene ring is substituted with two different groups. We have investigated for an asymmetric synthesis utilizing planar chiral (arene) chromium complexes in this research project.At first, enantiomerically active planar chiral (arene) chromium complexes were prepared by following methods. Racemic (omicron-substituted benzylalcohol) Cr(CO)_3 complexes were kinetically resolved by lipase in the presence of isopropenyl acetate into enantiomerically active chromium complexes in high enantiomeric excesses. Tricarbonylchromium-complexed protected phenol or aniline derivative was lithiated at the enantiotopic ortho position with chiral lithium diamine followed by quenching with electrophiles to give optically active (di-substituted arene) chromium complexes.Cross-coupling of (2,6-disubstituted halobenzene) chromium with o-substituted phenylboronic acids in the presence of palladium catalyst gave … More diastereoselectivelly Cr(CO)_3-complexed biaryls with complementary axial chirality depending upon the ortho-substituents of arylboronic acids. Reaction of omicron-alkyl or omicron-hydroxymethyl-substituted phenylboronic acid with (arylhalide) chromium complexes gave biaryls in which the ortho substituents are in a syn-orientation to the tricarbonylchromium fragment. With omicron-formyl phenylboronic acid, diastereoisomeric anti-coupling products were stereoselectively obtained. The kinetically controlled cross-coupling products were easily isomerized to themodynamically stable mono-Cr(CO)_3-complexed biaryls under the thermal conditions. The overall process can be considered to be an enantioselective preparation of both axially chiral biaryls starting from a single planar chiral (arene) chromium complex. This stereoselective formation method of axial chiral biaryls utilizing the planar chiral arene chromium complexes can be applied for the total synthesis of biologically active natural product (-) -steganone.Enantiomerically pure (o-substituted benzaldehyde) Cr(CO)_3 complexes were treated with samarium diiodide (II) to produce a single bis-tricarbonylchromium-complexed diphenyl ethane 1,2-diols with threo configuration.The two relative stereochemistries at the benzylic position were controlled by its adjacent planar chrality of arene ring. Similarly, treatment of enantiomerically pure tricarbonylchromium complexes of o-substituted phenyl aldimines with samarium diiodide gave enantiomerically 1,2-diamines after oxidative de-metalation. Less