【作者】 高爱萍；

【导师】 王梅；

【作者基本信息】 大连理工大学 ， 应用化学， 2006， 硕士

【摘要】 尽管人们对过渡金属络合物催化硫醚的不对称氧化反应已进行了广泛深入的研究,然而,探索高效实用的催化硫醚氧化的不对称催化体系一直是催化和有机合成领域中最受人关注的研究方向之一。我们设计合成了四个含有吡咯烷骨架的Salen-Mn（Ⅲ）络合物和八个手性Schiff碱配体。通过IR、¹H NMR、MS和元素分析等测试手段对络合物和配体结构进行了表征。以合成的Salen-Mn（Ⅲ）络合物和VO（acac）₂/Schiff碱为催化剂,分别以亚碘酰苯（PhIO）和双氧水（H₂O₂）为氧化剂,在不同的反应条件下考察了这两类催化体系在硫醚不对称催化氧化中的催化性能。 以含有吡咯烷骨架的Salen-Mn（Ⅲ）络合物为催化剂,PhIO为氧化剂,在催化硫醚的不对称氧化中得到了中等活性、高化学选择性和较低的对映选择性。极性溶剂对此反应的对映选择性略有影响。其中,对于底物苯甲硫醚,在THF溶剂中取得了较好的对映选择性;对于缺电子硫醚,在CH₃CO₂Et溶剂中给出了较高的对映选择性。添加剂4-苯基吡啶氮氧化物（PPNO）或三甲基氧化氨（MNO）对产物的对映选择性略有改善。除此以外,我们考察了催化剂吡咯烷骨架N原子上取代基的立体效应对催化反应的影响,随着取代基团体积的增大,产物的ee值有较明显提高。据此我们提出了这类催化体系催化氧化硫醚的反应机理。 由廉价的手性氨基醇与3,5-二溴或3,5-二碘水杨醛缩合得到的配体和VO（acac）₂原位形成的催化体系,在1mol%的催化剂（VO（acac）₂/配体=1/2,摩尔/摩尔）存在下,用H₂O₂作为氧源,室温下对芳基甲基硫醚的不对称催化氧化显示了很高的收率和化学选择性、中等至较高的对映选择性。与由（S）-苯丙氨醇和（R）亮-氨醇合成的配体相比,由（S）-缬氨醇得到的配体给出了更好的对映选择性。其中3,5-二碘水杨醛和（S）-缬氨醇缩合得到的配体,在缓慢滴加H₂O₂的条件下,以苯甲硫醚和对溴苯甲硫醚为底物时,ee值分别提高到88%和92%。研究表明,向VO（acac）₂/Schiff碱催化体系中加入羧酸或其盐类化合物并不能提高催化剂的催化性能。更多还原

【Abstract】 Although catalytic asymmetric oxidation of sulfides has been extensively investigated using transition metal complexes of various chiral ligands as catalysts. So far, the development of highly efficient and practical catalysts for this type of reactions is still an interesting challenge in modern catalytic and synthetic chemistry. Four chiral （pyrrolidine salen）Mn（III） complexes and eight Schiff-base ligands are synthesized. The structures of prepared ligands and complexes are characterized by many analytical methods such as IR, MS ¹H NMR and Elemental analysis. Under different reaction conditions, the catalytic performances in the asymmetric oxidation of sulfides are explored using two catalytic systems, chiral （pyrrolidine salen）Mn（III） complexes and VO（acac）₂/Schiff bases, with PhIO and H₂O₂ as oxidants respectively.With a series of chiral （pyrrolidine salen）Mn（III） complexes as catalysts for asymmetric oxidation of aryl methyl sulfides, moderate activity, good chemical selectivity and low to moderate enantioselectivity are attained using PhIO as oxidant. Enantioselectivity of sulfide oxidation is affected slightly by polar solvent and the sulfoxidation carried out in THF for thioanisole and in CH₃CO₂Et for electron deficient sulfides give better enantioselectivities. The addition of the donor ligand such as 4-phenylpyridine N-oxide （PPNO） or trimethylamine N-oxide （MNO） exhibits a minor positive effect on the enantioselectivity. Also we investigate the steric effect of the N_aza-substituent in the backbone of （pyrrolidine salen）Mn（III） complexes on the enantioselectivity of sulfide oxidation. An increase in the size of the R group on the N atom of the （pyrrolidine salen）Mn（III） complexs leads to an observable increase in the enantioselectivity. The sulfides’ access pathway is discussed based on the catalytic results.The catalytic system of VO（acac）₂ and chiral Schiff base ligands, derived from 3,5-dibromo- or 3,5-diiodosalicylaldehyde and inexpensive chiral amino alcohols, displays good yields and moderate to high enantioselectivities for the asymmetric oxidation of arylmethyl sulfides at room temperature using 1 mol% catalyst （VO（acac）2:ligand = 1:2, mol/mol） with H2O2 as oxidant. The ligands derived from S-valinol give considerably higher enantioselectivity than others derived from i’-phenylalaninol and i?-leucinol. Moreover, the ee values can be improved up to 88% for methyl phenyl sulfoxide and 92% for methyl /?-bromophenyl sulfoxide by slow dropwise-addition of H2O2 with the ligand prepared from S-valinol and 3,5-diiodosalicylaldehyde. Present studies show that the catalytic performance of VO（acac）2/Schiff base system can not be improved by addition of carboxylic acids or carboxylate salts.更多还原