CREATION OF TRIDENTATE TRANS-CHELATING CHIRAL LIGAND BASED ON A NEW MOLECULAR STRUCTURE DESIGN

建立有效的手性控制方法是21世纪世纪有机合成化学的中心课题之一。本研究设计并合成了一种新型的反式螯合三齿手性配体，其骨架为二苯并呋喃，在4-和6-位上分别含有两个恶唑啉取代基。通过对4，6-二苯并呋喃二基-2，2-双（4-苯基恶唑啉）（以下简称DBFOXIPh）的过渡金属配合物催化的不对称反应的研究，获得了如下新的发现和有用的信息：1. DBFOX/Ph配体与过渡金属离子如Mn（II）、Fe（II）、Co（II）、Ni（II）、Cu（II）、Zn（II）高氯酸盐六水合物形成稳定的络合物。有些配合物可以分离出来，表现出很高的催化活性，如刘易斯酸. DBFOX/Ph配体的镍（II）配合物水溶液可在潮湿条件下在空气中储存数月， ...更多信息 而不损失催化活性。镍配合物催化环戊二烯与3-丙烯酰基-2-恶唑环丁酮的Diels-Alder反应，表现出绝对的内选择性和对映选择性.与无水配合物相比，水相配合物表现出更高的对映选择性和催化活性.镍和锌配合物在催化的Diels-Alder反应中表现出非常有效的手性放大作用.提出了两种机理：（1）惰性梅萨2：1配合物在催化剂制备阶段的沉淀;（2）1：1配合物的异手性聚集体比同手性聚集体更稳定. 1：1络合物的聚集是基于水配体和高氯酸根离子之间的氢键作用。8.镍配合物在含有配位添加剂如水、醇、羧酸和胺的反应介质中显示出足够高的催化活性。镍和锌配合物在硝酮与3-巴豆酰基-2-恶唑烷酮的环加成反应中表现出优异的催化性能，表现出绝对的内选择性和对映选择性。在3-巴豆酰基-2-恶唑烷酮的重氮环加成反应中，锌配合物表现出很好的对映选择性，而镁配合物在3-巴豆酰基-4，4-二甲基-2-恶唑烷酮的重氮环加成反应中表现出很好的对映选择性，对映选择性完全相反。这一结果提供了一个有趣的例子“配体-辅助合作立体控制”。11.镍配合物催化硫醇与3-巴豆酰基-2-恶唑烷酮的共轭加成，以高对映选择性产生共轭加合物。少

Establishment 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 designed and synthesized a new trans-chelating tridentate chiral ligand which has a dibenzofuran skeleton having two oxazoline substituents at 4- and 6-positions. From the study of a wide variety of asymmetric reactions catalyzed by the transition metal complexes of this new ligand, 4,6-dibenzofurandiyl-2,2-bis(4-phenyloxazoline) designated hereafter as DBFOXIPh, new findings as well as useful informations have been obtained as shown below :1. DBFOX/Ph Ligand forms stable complexes with the transition metal ions such as Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(lI) perchlorate hexahydrates. Some complexes can be isolated and show high catalytic activity as Lewis acids.2. The aqua nickel(II) complex of DBFOX/Ph ligand can be stored for months in air under moisture conditions w … More ithout loss of catalytic activity.3. The nickel complex catalyzes the Diels-Alder reactions between cyclopentadiene and 3-acryloyl-2-oxazotidinone to show the absolute endo selectivity and enantioselectivity.4. Aqua complexes show even higher levels of enantioselectivity and catalytic activity than the anhydrous complexes.5. The nickel and zinc complexes show extremely effective chiral amplification in the catalyzed Diels-Alder reactions.6. Two mechanisms have been proposed : (1) the precipitation of inert mesa 2 : 1 complex in the preparation stage of catalyst, (2) the heterochiral aggregation of 1 : 1 complexes is more stable than the homochiral aggregation.7. The aggreagtion of 1 : 1 complexes is based on the hydrogen bonding working between the water ligand and the perchiorate ions..8. The nickel complex shows sufficiently high catalytic activity in the reaction medium containing coordinating additives such as water, alcohols, carboxylic acids, and amines.9. The nickel and zinc complexes work as excellent catalysts in the nitrone cycloadditions using 3-crotonoyl-2-oxazolidinone to show the absolute endo selectivity and enantioselectivity.10. The zinc complex works as excellent catalyst in the diazo cycloadditions to 3-crotonoyl-2-oxazolidinone to show the absolute enantioselectivity, On the other hand, the magnesium complex is the best in the reaction of 3-crotonoyl-4,4-dimethyl-2-oxazolidinone where the mode of enantioselectivity is completely reversed. This result offers an interesting example of "ligand - auxiliary coorperative stereo control".11. The nickel complex catalyzes the conjugate addition of thiols to 3-crotonoyl-2-oxazolidinone to produce the conjugate adducts in high enantioselectivities. Less