Asymmetric Reaction Utilizing Planar Chiral Arenes

当芳烃环被两个不同的基团取代时，基于平面手性，（eta6-芳烃）铬配合物以两种对映体形式存在。本课题研究了平面手性（芳烃）铬配合物的不对称合成。首先，采用以下方法制备了具有对映活性的平面手性（芳烃）铬配合物。在醋酸异丙酯存在下，脂肪酶对外消旋（组微米取代苯甲醇）Cr(CO)_3配合物进行了动力学分解，得到了对映体活性高的对映体过量铬配合物。三羰基铬络合保护苯酚或苯胺衍生物与手性锂二胺在对映位上锂化，然后与亲电试剂猝灭得到光学活性（二取代芳烃）铬配合物。在钯催化剂的作用下，（2,6-二取代卤代苯）铬与邻取代苯硼酸交叉偶联得到了具有轴向互补手性的Cr(CO)_3络合双芳基，这取决于芳硼酸的邻取代基。组微米-烷基或组微米-羟甲基取代苯硼酸与（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位的二芳基。以苯硼酸为原料，立体选择性地得到了非对映异构体的抗偶联产物。动力学控制的交叉偶联产物在热条件下容易异构成动力学稳定的单cr (CO)_3络合双芳基。整个过程可以被认为是从单平面手性（芳烃）铬络合物开始的轴向手性双芳基的对映选择性制备。这种利用平面手性芳烃-铬配合物立体选择性合成轴向手性双芳基化合物的方法可用于生物活性天然产物(-)-甾烷酮的全合成。用二碘化钐（II）处理对映体纯（邻取代苯甲醛）Cr(CO)_3配合物，制得单双三羰基铬络合二苯基乙烷1,2-二醇。在苯基位置的两种相对立体化学是由相邻的芳烃环的平面色度控制的。同样，用二碘化钐处理o取代苯基醛胺的对映纯三羰基铬配合物，氧化脱金属后得到对映1,2-二胺。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