DESIGN AND SYNTHESIS OF EFFICIENT CHIRAL CATALYSTS BASED ON CONFORMATIONAL CONTROL OF SHIELDING SUBSTITUENT

在不对称催化反应中，寻找有效的手性控制方法是21世纪有机合成化学的中心课题之一。在本研究中，我们面临的挑战是设计和合成高效的手性催化剂的基础上构象控制的利港骨架以及屏蔽取代基。一种是反式螯合三齿手性配体，其具有二苯并呋喃骨架，在4-和6-位具有两个恶唑啉取代基。另一种是一种常见的双吗啉型手性配体，具有邻羟基的苄基屏蔽取代基。这些配合物被发现有效地用于强配位亲核试剂的催化不对称反应.硝酮环加成：R，R-DBFOX/Ph配体的镍（II）水配合物在室温下以2mol%的催化负载量成功催化硝酮与3-丁烯酰基-2-恶唑烷酮及其衍生物的环加成反应，显示出优异的性能。 关于我们 非常高的非对映体和对映体选择性。使用单齿亲偶极试剂的硝酮环加成反应：使用溴丙烯醛作为单齿亲偶极试剂的硝酮环加成反应在R，R-DBFOX/Ph配体的锌（II）络合物的存在下进行得更有效。已经证明，该反应通过硝酮/催化剂/受体活化络合物的内部递送机制进行。重氮环加成：在10mol%的锌（Ⅱ）配合物R，R-DBFOX/Ph存在下，三甲基硅基重氮甲烷与3-巴豆酰基-2-恶唑烷酮及其衍生物的重氮环加成反应具有良好的对映选择性.另一方面，3-巴豆酰基-4，4-二甲基-2-恶唑烷酮的类似反应完全不能被锌（II）和镍（II）络合物活化，而是被镁络合物活化。结果表明，该反应具有较高的对映选择性，且反应模式相反.胺缀合物添加：研究了配体R，R-BOX/o-HOBn的铜（Ⅱ）配合物在O-苄基羟胺与3-异丙基-1-巴豆酰基-2-咪唑啉酮的胺共轭加成反应中的应用。这种反应也被认为是通过内部传递机制进行的。少

Development of a useful method of chirality control in catalyzed asymmetric reactions is one of the central subjects in the field of synthetic organic chemistry in 21st century. In the present research, we have challenged to design and synthesize efficient chiral catalysts based on conformational control of ligang skeleton as well as shielding substituents. One is a trans-chelating tridentate chiral ligand which has a dibenzofuran skeleton with two oxazoline substituents at 4- and 6-positions. The other one is a usual bisoxaloline type of chiral ligand having benzyl shielding substituents with o-hydroxyl moiety. These complexes are found to be effectively utilized in the catalyzed asymmetric reactions of strongly coordinating nucleophiles.1. Nitrone Cycloadditions : The nickel(II) aqua complex of R,R-DBFOX/Ph ligand successfully catalyzes the nitrone cycloaddition reactions to 3-crotonoyl-2-oxazolidinone and derivatives in the catalytic loading of 2 mol% at room temperature to show ext … More remely high diastereo- and enantioselectivities.2. Nitrone Cycloadditions Using Monodentate Dipolarophiles : The nitrone cycloaddition reactions using bromoacrolein as a monodentate dipolarophile proceed much more efficiently in the presence of the zinc(II) complexes of R,R-DBFOX/Ph ligand. It has been evidenced that this reaction proceeds through the internal delivery mechanism of the nitrone/catalyst/acceptor activated complex.3. Diazo Cycloadditions : Excellent enantioselectivity has been attained in the diazo cycloaddition reactions between trimethylsilyldiazomethane and 3-crotonoyl-2-oxazolidinone and derivatives in the presence of the zinc(II) complexes of R,R-DBFOX/Ph ligand (10 mol%). On the other hand, similar reactions of 3-crotonoyl-4,4-dimethyl-2-oxazolidinone can be activated not by the zinc(II) and nickel(II) complexes at all but the magnesium complex. The high enantioselectivities with the opposite mode have resulted.4. Amine Conjugate Additions : The copper(II) complex of R,R-BOX/o-HOBn ligand is found to be very useful in the amine conjugate addition reactions of O-benzylhydroxylamine to 3-isopropyl-1-crotonoyl-2-imidazolidinone. This reaction is also believed to proceed through the internal delivery mechanism. Less