共查询到19条相似文献,搜索用时 156 毫秒
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以生物碱奎宁和不同胺为原料,通过4步反应合成了5种新型手性胍催化剂,其结构经1H NMR, 13C NMR, IR和HR-MS(ESI)表征。探索了一系列奎宁衍生的手性胍催化剂催化硝基乙烯类化合物和硫代丙二酸酯的不对称Michael加成反应。通过优化反应条件,确定最佳条件为:5 mol% 5e为催化剂,乙醚为溶剂,于20 ℃反应5 h。在此条件下进行了底物拓展,获得一系列2-(1-芳基-2硝基乙基)丙二酸二苯二硫酯,最高收率为92%,最高对映选择性为93%。 相似文献
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在四乙氧基钛催化下,用天然丰产的冰片为手性源与苯乙酮酸乙酯进行酯交换得到含手性基团的苯乙酮酸冰片酯,苯乙酮酸冰片酯在冰片基的立体控制下与硝基甲烷缩合,主要得到2R-2-羟基-2-苯基-3-硝基丙酸冰片酯,用高效液相色谱法分析了诱导不对称Henry缩合反应效果,其e.e.值为56.5%,用IR、1HNMR、13CNMR确... 相似文献
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为设计一种利用廉价催化剂以达成C—H活化构建C—S的方法,本文研究了铜催化C—H活化/C—S偶联反应合成系列环烷基芳基硫醚化合物。以芳基磺酰肼与环烷烃为原料,溴化亚铜为催化剂,二叔丁基过氧化物(DTBP)为氧化剂,120℃反应24 h,经氧化脱氮C—H活化/C—S偶联串联反应过程,合成了系列环烷基芳基硫醚化合物。该反应适合环戊烷、环己烷、环庚烷、环辛烷和环十二烷等环烷烃和不同取代基团(甲氧基、硝基、氯和甲基)的芳基酰肼,合成得到了18个芳基硫醚类化合物,产率为41%~72%。其结构经1H NMR、13C NMR和HR-MS进行了表征。 相似文献
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以THF为溶剂, CuI/TMEDA为催化剂,四乙酰溴代葡萄糖与芳基溴化镁经取代反应合成了芳基葡萄糖碳苷(2a~2c),其结构经1H NMR和13C NMR确证。该方法立体选择性较好。在最佳反应条件(THF为溶剂,10% CuI和10% TMEDA为催化剂,于0 ℃反应至终点)下,2a~2c的收率为58%~71%, α/β为1/6.5~1/7.1。 相似文献
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In the presence of titanium(IV) tetraethoxide ((EtO)4Ti), menthyl arylglyoxylates are prepared by transesterification of ethyl arylglyoxylates and natural (−)‐(1R,2S,5R)‐menthol. Using menthyl as a chiral auxiliary, the corresponding novel (R)‐menthyl 2‐aryl‐2‐hydroxybutanoates are synthesized by the addition of Et2Zn with menthyl arylglyoxylates. The structures of the products are characterized by IR and 1H‐ and 13C‐NMR spectroscopy, mass spectrometry, and elemental analysis. The diastereoselectivities are analyzed by HPLC. The addition reactions are completed with good yields and high diastereoisomeric excess (de up to 95%), and, after hydrolysis, the (R)‐2‐aryl‐2‐hydroxybutanoic acids are obtained with high optical purities. 相似文献
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A. R. Hajipour M. Hantehzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):181-189
Abstract The addition of the lithium carbanion of (R)-(+)-3,4-dimethoxybenzyl 2-methoxy-1-naphthyl sulfoxide 3 to cyclic nitrone 4, under kinetically controlled conditions gave isoquinoline sulfoxide derivatives 5 and 6 in high diastereoselectivities, Under equilibrium controlled conditions poor diastereoselectivity results. The chiral (R)-(+)-3,4-dimethoxybenzyl 2-methoxy-I -naphthyl sulfoxide 3 was easily prepared by the reaction of 3.4-dimethoxyben-zylmagnesium chloride 2 with (-)-(S)menthyl 2-methoxy-naphthalenesulfinate 1 in dry benzene. This methodology allows for the synthesis of the isoquinoline alkaloid (R)-(-)-norlaudanosine 8 in three efficient synthetic steps. 相似文献
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(+)-(1S,2S,5R)-8-联苯薄荷醇的合成 总被引:4,自引:0,他引:4
以(R)-( )-pu legone为起始原料,经1,4-加成,还原两步反应合成了手性辅助试剂( )-(1S,2S,5R)-8-联苯薄荷醇及其差向异构体(-)-(1R,2S,5R)-8-联苯薄荷醇,总产率95%。其结构经1H NMR,13C NMR,IR,MS和X-射线衍射仪表征。 相似文献
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《Tetrahedron: Asymmetry》2003,14(8):971-974
An asymmetric synthesis of β-iodo-α-(hydroxyalkyl)acrylates has been developed involving conjugate addition of I− to menthyl propiolates to give β-iodo allenolate intermediates which undergo 1,2-addition to form β-iodo Baylis–Hillman products. Modest diastereoselectivities (37–58% de) and excellent yields (80–87%) were obtained when (1R,2S,5R)-(−)-menthol was used as a chiral auxiliary. The two diastereoisomers of the product were separated by silica gel chromatography to give diastereomerically pure products. 相似文献
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不对称Reformatsky反应的研究 总被引:2,自引:0,他引:2
分别将催化计量和化学计量的(1R, 2S)或(1S, 2R)-2-氨基-1,2-二苯基乙醇衍生的手性氨基醇配体1应用于催化不对称Reformatsky反应, 研究了手性配体的结构及其用量与反应对映选择性的关系, 溶剂和底物改变对e.e.值的影响; 并设计与研究了双手性体系, 使该反应在催化量(25mol%)手性配体的作用下, 得到中等对映选择性; 另外, 还比较了不同的实验方法对反应的对映选择性的影响, 提出了手性催化循环机理和反应过渡态模型, 能较好地解释一系列实验事实。 相似文献
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Kinetic resolution of acyclic secondary allylic silyl ethers by chiral dioxiranes generated in situ from chiral ketones (R)-1 and (R)-2 and Oxone was investigated. An efficient and catalytic method has been developed for kinetic resolution of those substrates with a CCl(3), tert-butyl, or CF(3) group at the alpha-position. In particular, high selectivities (S up to 100) were observed for kinetic resolutions of racemic alpha-trichloromethyl allylic silyl ethers 7 and 9-15 catalyzed by ketones (R)-2. Both the recovered substrates and the resulting epoxides were obtained in high enantiomeric excess. On the basis of steric and electrostatic interactions between the chiral dioxiranes and the racemic substrates, a model was proposed to rationalize the enantioselectivities and diastereoselectivities in the chiral ketone-catalyzed kinetic resolution process. 相似文献
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Functional phenylacetylene derivatives containing l-alanine and l-leucine moieties with chiral menthyl and achiral n-octyl terminal groups {HC[triple bond]C-C6H4-p-CONHCH(R)CO2R': R = CH3, R'= (-)-(1R,2S,5R)-menthyl [1(-)]; R = CH2CH(CH2)3, R' = (-)-(1R,2S,5R)-menthyl [2(-)]; R'= CH2CH(CH2)3, R' = (+)-(1S,2R,5S)-menthyl [2(+)]; R'= CH2CH(CH2)3, R' = (CH2)7CH3 (2o)} are synthesized. Polymerizations of the acetylene monomers are effected by organorhodium catalysts, giving corresponding polymers P1(-), P2(-), P2(+), and P2o of high molecular weights (Mw up to 1.2 x 10(6)) in high yields (up to 89%). The polymers are thermally stable (Td >or= 300 degrees C) and soluble in common organic solvents. The polymer structures are characterized by IR, NMR, UV, and CD spectroscopies. Intense CD signals are observed in the visible spectral region, indicating that the polymer chains are taking a helical conformation with an excess of preferred handedness. The backbone conjugation and chain helicity of the polymers can be tuned by changing their molecular structures [(a)chiral pendant groups] and by applying external stimuli (solvent and pH). Addition of trifluoroacetic acid to the polymer solutions decreases their molar ellipticities and enhances their backbone conjugations, inducing a halochromism with a continuous and reversible color change (yellow <==> red). 相似文献