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以天然手性产物L-脯氨酸为原料,经酯化、氨基保护和格氏反应,得到一种新型光学活性的脯氨醇衍生物((S)-N-苄基-2-吡咯烷-α,α-二(α-萘基)甲醇1).1经过催化氢解,得到另一种光学活性脯氨醇衍生物((S)-2-吡咯烷-α,α-二(α-萘基)甲醇2).将1和2作为有机催化剂,用于催化二烷基锌和醛的不对称加成反应.分别考察了影响对映选择性的催化剂结构、催化剂用量、溶剂、反应温度等各种因素.结果表明,当催化剂用量为5%、溶剂为甲苯、反应温度为-10℃,1作催化剂时,所得仲醇的对映体过量达82?,产率高达100%. 相似文献
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以商业化易得的具有碱性氮原子的手性药物为有机催化剂,用于催化β-酮酸酯不对称α-羟基化反应,发现以噻吗洛尔或普萘洛尔为催化剂,反应对映选择性分别可达32%和18%.对噻吗洛尔和普萘洛尔进行结构修饰,合成了12个洛尔药物类似物,并考察了其催化效果,发现在优化的反应条件下,以30mol%(R)-1-叔丁胺基-3-(2-萘氧基)-2-丙醇(7f)为催化剂,20mol%β-环糊精为助催化剂,叔丁基过氧化氢为氧化剂,正己烷为溶剂,反应对映选择性最高可达57%,收率92%.不对称α-羟基化产物(S)-5-氯-2-羟基-1-茚酮-2-甲酸甲酯(2a)在乙酸乙酯中一次重结晶后,对映体光学纯度可达99%,收率68%. 相似文献
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首次以L-脯氨酰胺为催化剂,通过不对称Robinson环化反应合成了Wieland-Mieschert酮,化学产率和对映选择性中等。 相似文献
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新型双芳烃桥连的salen钛配合物是一种高活性的催化三甲基硅腈对醛不对称加成反应的催化剂,底物与催化剂用量比率可达1 000:1.由(R,R)-1,2.环已二胺和3,5-二叔丁基水杨醛合成的催化剂4在催化三甲基硅腈对醛不对称加成反应中达到87%的对映选择性. 相似文献
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以方酸二甲酯及N-酰基-L-脯氨醛为原料,合成了4种新型方酰胺-N-酰基吡咯烷双功能手性催化剂,利用~1H NMR,~(13)CNMR,HR-MS,IR对催化剂结构进了表征。将该类催化剂应用于2,4-戊二酮对硝基烯烃的不对称Michael加成反应中,考察了溶剂、温度和催化剂用量对反应的影响,得到的最优反应条件为:甲苯为溶剂,催化剂用量为0.5 mol%,室温下反应。在最优反应条件下,以3a为催化剂,合成了12个具有光学活性的3位取代的2,4-戊二酮,最高产率达到97%,最高ee值达到95%。该催化体系能够适合含有吸电子和供电子基团的各种硝基烯烃的不对称加成。 相似文献
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《Tetrahedron: Asymmetry》2014,25(24):1599-1604
Two chiral aromatic l-prolinamides were synthesized in high overall yield (95%) from N-Boc-l-proline and served as organocatalysts in asymmetric Michael reactions of aldehydes to nitroalkenes. Under the optimized reaction conditions, (S)-N-tritylpyrrolidine-2-carboxamide 4 was found to be a highly efficient organocatalyst for the Michael addition, and the corresponding Michael adducts were obtained in good yields (up to 94%), with excellent enantioselectivities (up to 99% ee) and diastereoselectivities (up to 99:1 dr). 相似文献
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Amarjit Kaur Kamal Nain Singh Esha Sharma Poonam Rani Sandeep Kumar Sharma 《Tetrahedron》2018,74(42):6137-6143
The novel ((S)-pyrrolidin-2-yl)methyl phenylcarbamate was synthesized and used as an efficient organocatalyst for the asymmetric Michael addition of cyclic/acyclic ketones to nitroolefins. Interestingly, the resulting Michael adducts were obtained in good to high yields (up to 96%) with excellent stereoselectivity (ee up to >99%, dr up to >99:1) without using any additive. 相似文献
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Matsunaga S Kinoshita T Okada S Harada S Shibasaki M 《Journal of the American Chemical Society》2004,126(24):7559-7570
Synthesis and application of alpha,beta-unsaturated N-acylpyrroles as highly reactive, monodentate ester surrogates in the catalytic asymmetric epoxidation and Michael reactions are described. alpha,beta-Unsaturated N-acylpyrroles with various functional groups were synthesized by the Wittig reaction using ylide 2. A Sm(O-i-Pr)(3)/H(8)-BINOL complex was the most effective catalyst for the epoxidation to afford pyrrolyl epoxides in up to 100% yield and >99% ee. Catalyst loading was successfully reduced to as little as 0.02 mol % (substrate/catalyst = 5000). The high turnover frequency and high volumetric productivity of the present reaction are also noteworthy. In addition, a sequential Wittig olefination-catalytic asymmetric epoxidation reaction was developed, providing efficient one-pot access to optically active epoxides from various aldehydes in high yield and ee (96-->99%). In a direct catalytic asymmetric Michael reaction of hydroxyketone promoted by the Et(2)Zn/linked-BINOL complex, Michael adducts were obtained in good yield (74-97%), dr (69/31-95/5), and ee (73-95%). This represents the first direct catalytic asymmetric Michael reaction of unmodified ketone to an alpha,beta-unsaturated carboxylic acid derivative. The properties of alpha,beta-unsaturated N-acylpyrrole are also discussed. Finally, the utility of the N-acylpyrrole unit for further transformations is demonstrated. 相似文献
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A novel and effective organocatalytic system consisting of pyrrolidinyl-thioimidazole and a chiral thioureido acid efficiently catalyzed the asymmetric Michael addition reactions of ketones to nitroolefins to afford the adducts with high diastereoselectivities (up to 99 : 1) and excellent enantioselectivities (up to 99% ee). 相似文献
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A series of chiral pyrrolidine quaternary derivatives were designed and synthesized. It was found that these derivatives are highly efficient organocatalysts for the asymmetric Michael addition reactions of aldehydes and ketones to nitroolefins with high yields (up to 96%), high enantioselectivities (up to 99% ee), and high diastereoselectivities (up to 97:3 dr). Furthermore, catalyst 7a could be recycled without remarkable loss of catalytic activity and stereoselectivity. 相似文献
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Perhydroindolic acids, the by-products obtained in the industrial production of a trandolapril intermediate, were used as chiral organocatalysts in asymmetric Michael addition reactions of aldehydes to nitroolefins. These proline-like catalysts are unique for their rigid bicyclic structure with two H atoms attached to the bridgehead C atoms lying on the opposite side of the ring. They therefore showed high efficiency in asymmetric Michael additions of aldehydes to nitroolefins. Under the optimal conditions, excellent diastereo- and enantioselectivities (up to 99/1 dr and 98% ee) were obtained with high chemical yields for a series of aldehydes and nitroolefins using only 5 mol% catalyst loading. The methodology features easily available catalysts, high catalytic efficiency and environmentally green procedures. 相似文献
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Hamashima Y 《Chemical & pharmaceutical bulletin》2006,54(10):1351-1364
Using the unique character of the chiral Pd complexes 1 and 2, highly efficient catalytic asymmetric reactions have been developed. In contrast to conventional Pd(0)-catalyzed reactions, these complexes function as an acid-base catalyst. Thus active methine and methylene compounds were activated to form chiral palladium enolates, which underwent enantioselective carbon-carbon bond-forming reactions such as Michael reaction and Mannich-type reaction with up to 99% ee. Interestingly, these palladium enolates acted cooperatively with a strong protic acid, formed concomitantly during the formation of the enolates to activate electrophiles, thereby promoting the C-C bond-forming reaction. This palladium enolate chemistry was also applicable to electrophilic enantioselective fluorination reactions, and various carbonyl compounds including beta-ketoesters, beta-ketophosphonates, tert-butoxycarbonyl lactone/lactams, cyanoesters, and oxindole derivatives could be fluorinated in a highly enantioselective manner (up to 99% ee). Using this method, the catalytic enantioselective synthesis of BMS-204352, a promising anti-stroke agent, was achieved. In addition, the direct enantioselective conjugate addition of aromatic and aliphatic amines to alpha,beta-unsaturated carbonyl compound was successfully demonstrated. In this reaction, combined use of the Pd complex 2 having basic character and the amine salt was the key to success, allowing controlled generation of the nucleophilic free amine. This aza-Michael reaction was successfully applied to asymmetric synthesis of the CETP inhibitor torcetrapib. 相似文献
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An efficient procedure for asymmetric Michael addition reaction of cyclic ketones with low activated chalcones catalyzed by pyrrolidine-based phthalimide and 1,8-Naphthalimide catalysts was developed. The corresponding products were obtained in high yields with high diastereoselectivities (up to 99:1 dr) and high enantioselectivities (up to 96% ee) under mild conditions. 相似文献
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Chao Wang 《Tetrahedron letters》2009,50(20):2363-2296
4-Trifluoromethanesulfonamidyl prolinol tert-butyldiphenylsilyl ether bifunctional organocatalyst 3a is a highly efficient catalyst for the asymmetric Michael addition reactions of ketones and aldehydes to nitrostyrenes, leading to syn-selective adducts with excellent yields (>99%), high diastereoselectivities (up to 99:1 dr) and excellent enantioselectivities (up to 99% ee). Control experiments suggested that the trans-configuration relationship between the bulky group (-CH2OTBDPS) and the sulfonamido group at the 4-position of the pyrrolidine ring was important to achieve high yield and stereoselectivity. 相似文献
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The first organocatalytic enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes for the direct synthesis of chiral nitroalkylated naphthoquinone derivatives was investigated. Good yields and excellent enantioselectivities (up to >99% ee) could be achieved. This organocatalytic asymmetric Michael addition provides an efficient route toward the synthesis of optically active functionalized naphthoquinones. 相似文献