【作者】 单凤军；

【导师】 李争宁；

【作者基本信息】 大连大学 ， 有机化学， 2011， 硕士

【摘要】 含氮杂环卡宾(NHC)及其金属络合物的化学是近二十年来发展起来的新领域。NHC作为一种新型的配体,它们可与过渡金属离子配位,形成稳定性较好的配合物,在多类催化反应中表现出独特的魅力,其中手性NHC及其金属配合物在不对称催化反应中发挥着越来越重要的作用,显示出重要的学术及应用价值。在本论文中,我们设计了具有C2对称性的螯合型五元、六元NHC的前体,其环上氮原子的取代基中带潜在配位的氧原子,脱除质子后可形成多齿NHC配体,与金属配位时形成的螯合物在催化不对称反应时可能获得更高选择性。由于它们特殊的配位能力,与传统的有机膦配体不同、在催化反应等领域与机膦配体互补。本文采用以下不同路线合成了具有上述结构特征的NHC前体咪唑盐、咪唑啉盐、四氢嘧啶盐。这些路线包括:(1)以手性的氨基醇(醚)为原料与草酸二乙酯反应形成酰胺、再用LiAlH4还原酰胺得到二胺,最后通过与原甲酸乙酯、氟硼酸铵(氯化铵等)作用关环形成咪唑啉盐七种;(2)以氨基醇为原料与1,2-二溴乙烷反应得到二胺,再经过与原甲酸乙酯、氟硼酸铵(氯化铵等)作用关环形成咪唑啉盐三种;(3)乳酸酯(或扁桃酸酯)为原料,经酚醚化、还原酯为醇、对甲苯磺酰化,溴代,最后与咪唑反应得到咪唑盐六种;(4)以苯基环氧乙烷和咪唑在加压的条件下反应,得到咪唑盐一种;(5)以胺和乙二醛为原料合成二亚胺,再用多聚甲醛、TMSCl进行关环,得到咪唑盐二种;(6)类似与路线(2),但使用1,3-二溴乙烷反应,得到了六元环的3,4,5,6-四氢嘧啶盐六种。对氨基醇与乙二醛间的反应,得到了双噁唑螺环化合物,而非未得到预期的产物二胺。将合成的咪唑(啉)盐、嘧啶盐经脱质子后生成的螯合型NHC用于催化反应。以咪唑(啉)盐原位形成的NHC-Cu化合物催化二乙基锌对环己(戊)烯酮的不对称共轭加成反应。当使用咪唑啉盐时,获得了较高的化学收率(99%)和合理的ee值(78%)。使用不同的碱,优势产物的构型会发生改变。这些咪唑(啉)盐、嘧啶盐-碱-Cu(I)原位形成的化合物也能催化硅氢试剂对α,β-不饱和酮的共轭还原反应。其中咪唑盐形成的催化剂表现出较好的催化性能和选择性,能使反应在5 min内完成,且只还原其中的碳碳双键,得到近乎定量收率的选择性还原产物。更多还原

【Abstract】 The chemistry of N-heterocyclic carbene (NHC) and its metal complexes is a new and active research area in the last two decades. NHC, a novel type of ligand, can coordinate with transition metal ions, forming complexes with good stability and unique quality in many catalytic reactions. In recent years, their catalytic properties in asymmetric version have been highlighted, both with academic interest and technical importance.In this thesis, we have designed five- membered-ring, and six-membered-ring NHC precursors with a C2 symmetry, where substitutents attached to nitrogen atoms of the ring have potentially coordinative oxygen atoms. Therefore, these NHC might act as multi-dentated ligand when coordinating with metal ions, and exhibit different, hopefully more excellent catalytic abilities, when compared with the current popular mono-dentate NHC ligands. Due to their special coordinative property and topology, they might be different, or even as an alternative, to the traditional phosphorous ligand.The following routes were employed in this thesis, for the synthesis of imidazolium salts, imidazolinium salts and 3,4,5,6-tetrahydropyrimidinium salts, the precursor of C2-symmetric NHC: (1) amides obtained from chiral amino alcohol (ether) and diethyl oxalate were reduced with LiAlH4, yielding diamines, the latter ones reacted with ethyl orthoformate and ammonium tetrafluoroborate (or ammonium chloride etc.), furnishing seven imidazolinium salts; (2) diamines derived from the reaction between amino alcohols and 1,2-dibromoethane reacted with ethyl orthoformate and ammonium tetrafluoroborate (ammonium chloride etc.), providing three imidazolinium salt; (3) the hydroxy group in alkyl lactate (mandelate) was converted into the corresponding ethers, and then the formed esters were reduced to alcohols, and the alcohol was converted to bromide; finally, the bromides reacted with imidazole giving six imidazolium salts; (4) one imidazolium salt was produced via the reaction of styrene oxide with imidazole under pressure; (5) two imidazolium salts were obtained via the cyclization of diimine derived from amine and glyoxal, with paraformaldehyde in the presence of trimethylsilyl chloride; (6) a similar reaction to route (2), but 1,3–dibromopropane was used and six six-membered ring 3,4,5,6-tetrahydropyrimidinium salts were obtained.Reaction of amino alcohols with glyoxal was also investigate, however, spiro bisoxazolidine compounds, instead of the expected diamines, were produced.The synthesized imidazolium salts were used as the NHC precursor in catalytic reactions. Cu-NHC compounds formed in situ from imidazolium (imidazolinium) salts were applied to the asymmetric conjugate addition of Et2Zn to cyclohexenone and cyclopentenone. In the presence of imidazolinium salts, high chemical yield (up to 99%) and reasonable ee (up to 78%) were achieved. It is interesting that using different bases may result in the switch of the configuration of the major product.The imidazolium salts were also applied to the Cu-promoted conjugate reduction ofα,β-unsaturated ketones with silane. Catalysts derived from imidazolium salts showed good catalytic properties and selectivity. The reaction could be finished in just 5 min, and only polar C-C double bond was reduced.更多还原