(3-氮-吗啉)-1-(4-氯)-苯基-1-丙酮不对称还原产物光学活性的理论计算

采用AM1方法对(S)-4-苄基-5,5-二苯基-1,3,2-噁唑硼烷催化(3-氮-吗啉)-1-(4-氯)-苯基-1-丙酮不对称还原反应的立体控制步骤进行了计算,获得了R和S型过渡态的优化构型及其热焓和熵等热力学参数,计算得到了该步反应中生成R和S型对映体的反应速率常数之比,据此得到的不对称还原反应最终产物的光学活性e.e.的理论计算值,与实验结果相近.     

脯氨酸催化丙酮与异丁醛不对称直接Aldol反应的DFT研究

采用密度泛函DFT-B3LYP方法计算研究了(S)-脯氨酸催化丙酮和异丁醛的不对称直接羟醛缩合(A l-dol)反应,得到了两种烯胺中间体及立体控制步骤中的四个立体异构过渡态的优化构型和相对能量,解释了该不对称反应的立体选择性.     

脯氨酸二肽催化的不对称直接Aldol反应

以(S)-脯氨酸和(R)-脯氨酸为原料合成了二肽H-(S)-Pro-(S)-Pro-OH(1)和H-(S)-Pro(-R)-Pro-OH(2),分别以两种二肽催化了不对称直接A ldol反应,获得了相同立体构型(S)的产物,与(S)-脯氨酸催化所得的产物构型(R)相反.该催化剂的立体选择性不高(ee<21%).理论计算的结果与实验结果吻合.     

β-氨基酮不对称还原反应的理论研究

本文用AM1半经验分子轨道方法,首次从热力学和动力学角度研究了(R)-4-苄基-5,5-二苯基-1,3,2口恶唑硼烷催化还原系列β-氨基酮的反应,获得了CBS 反应机理各步的反应热及第二、第四步骤的反应活化能,结果表明第二步(催化配合物的形成)和第四步(产物的形成和催化剂的释放)为吸热反应,且第四步反应吸热较多,且活化能远高于第二步,同时发现CBS反应机理中第二步为控制反应产物构型取向的决定步骤,根据第二步反应中生成R和S型催化配合物的活化能之差可推测β-氨基酮分子中羰基对位推电子基的存在有利于获得高光学活性的氨基醇产物。     

有效控制活性酵母细胞催化β-羰基酯不对称还原反应立体选择性的研究

 以4-氯乙酰乙酸乙酯为β-羰基酯的模型底物,对面包酵母催化其不对称还原反应立体选择性的控制进行了研究. 实验发现,利用诸如烯丙基醇和烯丙基溴等酶抑制剂对面包酵母进行预处理,可以控制反应的立体选择性. 用烯丙基醇预处理面包酵母时可以提高S型产物的立体选择性; 用烯丙基溴预处理时,可以使反应的立体选择性从通常的S型产物转变为R型产物. 立体选择性随着预处理时抑制剂浓度的增大和处理时间的延长而提高. 合适的预处理条件可使S型和R型产物的ee值分别达到95%和98%.     

聚偏二氯乙烯负载金鸡纳碱催化剂的合成及其对不对称Michael反应的催化性能

将天然的金鸡纳碱——辛可宁与聚偏二氯乙烯进行接枝反应,制备了聚偏二氯乙烯负载辛可宁的催化剂.将制备的催化剂用于催化不对称Michael反应,并探索了溶剂、催化剂用量、温度、底物等不同条件对其催化性能的影响.结果表明,该催化剂在甲苯中有很高的催化活性和较好的立体选择性,Michael反应中部分产率达到80%以上,e.e值达到72%,且该催化剂具有一定的重复使用性能.     

S-脯氨酸催化丙酮与2,2-二甲基丙醛不对称直接羟醛缩合反应过渡态的理论研究

采用从头计算和密度泛函方法研究了S-脯氨酸催化丙酮和2,2-二甲基丙醛的不对称Aldol反应的立体控制步骤, 同时考虑了DMSO溶剂效应, 计算得到了四个立体异构过渡态的优化构型及其相对能量, 解释了该不对称反应的立体选择性.     

Merrifield树脂负载的L-脯氨酰L-苏氨酸二肽催化剂的合成及其对不对称Aldol反应的催化性能

制备了Merrifield树脂负载的L-脯氨酰L-苏氨酸二肽催化剂.将制备的催化剂用于催化直接不对称Aldol反应,并探索了溶剂、表面活性剂、催化剂用量、底物等不同条件对其催化性能的影响.结果表明,该催化剂在Tween-20水溶胶束中有很高的催化活性和较好的立体选择性,Aldol反应中部分产率达到85%以上,e.e.值达到78%,且该催化剂具有一定的重复使用性能.     

微水相中改性Ultrastable-Y分子筛固定化脂肪酶拆分(R,S)-2-辛醇

采用改性Ultrastable-Y分子筛固定化P. expansum PED-03脂肪酶(PEL), 利用固定化PEL在微水相中对(R,S)-2-辛醇进行拆分. 结果表明, 改性Ultrastable-Y分子筛固定化PEL所催化的拆分反应的转化率(c)和对映体过量值(e.e.)以及对映体选择性(E)均得到大幅度提高. 介质类型和体系含水量对酶促拆分反应有较大的影响. 在以正己烷为溶剂, 含水量为0.8%的体系中, 于50 ℃反应24 h的转化率(c)可达到理论值的97.68%, 对映体过量值(e.e.)可达到98.75%. 改性Ultrastable-Y分子筛固定化PEL催化效率高、立体选择性强, 且催化性能稳定, 在(R,S)-2-辛醇的酶法拆分方面具有良好的应用前景.     

由(1R,2S)-麻黄碱制备的硼杂噁唑烷催化甲硼烷不对称还原苯乙酮

由(1R,2S)-麻黄碱制得了五个新的手性硼杂(口恶)唑烷1～5,它们催化甲硼烷不对称还原苯乙酮,获得了高产率的具有38.5～72.4％e.e.的R-1-苯基乙醇。讨论了催化剂的结构-活性关系及反应参数(催化剂用量、反应温度)对还原反应对映选择性的影响。     

几个新型噁唑硼烷的制备与应用

以(1S,2S)-2-氨基-1-(4-硝基苯)-1,3-丙二醇为原料,得到四种噁唑硼烷,原? 淮呋鹜椴欢猿苹乖笆中苑蓟致哿朔从ξ露群痛呋两峁苟苑从峁挠跋臁? $601$ATwonewtypesof1,3,2-oxaborolidineswerepreparedfrom(1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diolandusedascatalystsintheasymmetricreductionofacetophenone.Theinfluenceoftemperatureaswellastheeffectofthestructureofcatalystontheenantioselectivityisdiscussed.Theoriginoftheproducts'configurationalisexplored.     

Novel sterically congested chiral tripodal phosphite ligands: catalytic asymmetric hydrosilylation of ketones with a Rh(I)–TRISPHOS catalyst

A new chiral trisphosphite ligand, (S,S,S)-2,2′,2″-tris(2,4,8,10-tetra-tert-butyl-dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl-6-oxy)tri-2-propylamine, (S,S,S)-TRISPHOS, was synthesized and coordination chemistry investigated. The Rh(I)–(S,S,S)-TRISPHOS complexes were found to be effective catalysts for the enantioselective hydrosilylation of ketones.     

Chiral 1,3,2‐Diazaphospholenes as Catalytic Molecular Hydrides for Enantioselective Conjugate Reductions

Secondary 1,3,2‐diazaphospholenes have a polarized P?H bond and are emerging as molecular hydrides. Herein, a class of chiral, conformationally restricted methoxy‐1,3,2‐diazaphospholene catalysts is reported. We demonstrate their catalytic potential in asymmetric 1,4‐reductions of α,β‐unsaturated carbonyl derivatives, including enones, acyl pyrroles, and amides, which proceeded in enantioselectivities of up to 95.5:4.5 e.r.     

4,5,6,7-Tetrachlorobenzo[d][1,3,2]dioxaborol- 2-ol as an effective catalyst for the amide condensation of sterically demanding carboxylic acids

[reaction: see text] 4,5,6,7-Tetrachlorobenzo[d][1,3,2]dioxaborole (4a) and 4,5,6,7-tetrachlorobenzo[d][1,3,2]dioxaborol-2-ol (4b) are effective catalysts for the dehydrative amide condensation between an equimolar mixture of carboxylic acids and amines. In particular, these catalysts are greatly superior to 3,5-bis(trifluoromethyl)phenylboronic acid (1) for the amide condensation of sterically demanding carboxylic acids. In contrast, 4c, which is prepared from a 1:2 molar mixture of B(OH)(3) and tetrachlorocatechol, is effective as a Lewis acid-assisted Br?nsted acid (LBA) catalyst for Ritter reaction.     

Origin of the chemical stability of phosphine‐phosphoramidites: structural study of an UPPhos‐type crystal and application of UPPhos in the asymmetric hydrogenation of imines

Phosphine–phosphoramidites (PPAs) are heterobidentate ligands that have been developed in the last two decades and have been used successfully in asymmetric catalytic reactions. A single crystal of the PPA (11bS )‐N‐[(2S ,4S )‐4‐(diphenylphosphanyl)pentan‐2‐yl]‐N‐methyldinaphtho[2,1‐d :1′,2′‐f ][1,3,2]dioxaphosphepin‐4‐amine, C₃₈H₃₅NO₂P₂, was prepared and structurally characterized by single‐crystal X‐ray diffraction and density functional theory (DFT) calculations. Structure elucidation revealed unique features which might have a significant effect in the excellent chemical stability of this type of molecule. The conformation of the molecule provides an optimal chelating structure. Iridium complexes of UPPhos were found to be efficient catalysts in the asymmetric hydrogenation of imines {UPPhos is (11bS )‐N‐[(2S ,4S )‐4‐(diphenylphosphanyl)pentan‐2‐yl]‐N‐(propan‐2‐yl)dinaphtho[2,1‐d :1′,2′‐f ][1,3,2]dioxaphosphepin‐4‐amine}.     

Chiral oxazaborolidines bearing a 1- or 2-naphthylmethyl group as catalysts for the enantioselective borane reduction of ketones: experimental and quantum chemical calculations

Two new catalysts for the enantioselective reduction of ketones, chiral 1,3,2-oxazaborolidines substituted at carbon 4 by a 1- or 2-naphthylmethyl group, have been prepared from the related amino alcohols, by treatment with borane in tetrahydrofuran, and the effectiveness of these two catalysts has been investigated. The stereochemical outcomes were verified by means of quantum calculations using the AM1 computational method.     

Synthesis of New Ligand 1,2-Bis{di[（R,R）-1,3,2-oxzaphosphlidine]phosphino}ethane with C_2-symmetric Axis and Application in Rh-catalyzed Asymmetric Hydrogenation

New ligand 1,2-bis{di[（R,R）-1,3,2-oxzaphosphlidine]phosphino}ethane [（R,R）-BDOPPEs 1,2,3 and 4] with C2-symmetric axis and bearing nitrogen and oxygen were synthesized from readily available optically active amino alcohols.Rh complexes with these ligands were highly enantioselective catalysts for asymmetric hydrogenation of N-benzoyldehydroamino acid derivatives and α-functionalized ketones in 99%e.e.and 98%e.e.,respectively.This new class of（R,R）-BDOPPEs 1,2,3 and 4 gave much more effectivity and enantionselectivity than their corresponding non-C2-asymmetric aminophosphine phosphinite.     

A new series of chiral catalysts for the enantioselective borane reduction of ketones

A new series of 1,3,2-oxazaborolidine catalysts substituted in position 4 by the (CH3)3C(CH2)n group (n=2, 3, 4, 5) were synthesized and applied to the borane reduction of prochi-ral ketones. The relationship between catalyst structure and enantioselectivity was discussed.