关键词： asymmetric synthesis   chirality   solid-phase synthesis   substitution   sulfoximine  

摘要： An asymmetric synthesis of cycloalkenyl and alkenyloxiranes from allylic sulfoximines and aldehydes is described. Lithiation and titanation of cyclic and acyclic allylic sulfoximines with chlorotris(diethylamino)titanium and subsequent treatment with aldehydes gave, as described previously, enantio- and diastereomerically pure, syn-configured, sulfoximine-substituted homoallylic alcohols. Treatment of the sulfoximine-substituted homoallylic alcohols with chloroethyl chloroformate resulted in a facile substitution of the sulfoximine group by a Cl atom, with formation of the corresponding alkenyl chlorohydrins. In the case of the cycloalkenyl derivatives the substitution proceeded with high diastereoselectivities with retention of configuration, while in the case of the alkenyl derivatives, medium diastereoselectivities with inversion of configuration were observed. While elimination reactions of the cycloalkenyl chlorohydrins gave the corresponding enantio- and diastereomerically pure cis-configured cycloalkenyloxiranes in good overall yields, the alkenyl chlorohydrins afforded mixtures of enantiomerically pure trans and cis isomers in which the trans isomers dominated. The solution-phase synthesis was extended to the solid phase by the synthesis of an enantiomerically pure, polymer-bound allylic sulfoximine and its conversion into an alkenyloxirane. The initial results proved that the concept of the utilization of the sulfoximine group as a traceless chiral linker is feasible and suggest that the solid-phase asymmetric synthesis of cycloalkenyloxiranes by this route should be possible. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

关键词： asymmetric synthesis   enantioselectivity   chiral tether   chiral perturbation  

摘要： The 2,4-pentanediol (PD)-tethered reaction is a stereocontrolled reaction having versatile applicability. When reactant and reagent elements are connected through a PD tether prior to their reaction, stereochemical purity of the product is very high for nine different types of reactions so far studied. Selectivity of one of the reactions shows temperature independency over a wide range from -78 to 150 degreesC, which indicates that the stereocontrol is driven by the entropy term. The strict stereocontrol of this reaction at high temperatures can be extended to vapor phase reactions performed above 250 degreesC. To understand how the two methyl groups on the PD tether stereocontrol the reaction, a new parameter, a chiral perturbation factor, is introduced. By this analysis, it is disclosed that the methyl groups promote an activation entropy change for both the diastereomeric processes, and the strict stereocontrol is achieved when the changes have opposite signs. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).

关键词： 四甲基二硅桥联茚基环戊二烯基四羰基二铁   合成   晶体结构   热重排反应   硅硅键   铁铁键   不对称合成  

摘要： ClMe2 SiSiMe2 Cl顺序与茚基锂和环戊二烯基锂作用 ,生成 (1 C9H7)Me2 SiSiMe2 C5H5.后者进一步与五羰基铁反应 ,得到硅硅桥联茚基环戊二烯基化合物 [η5,η5 (1 C9H6)Me2 SiSiMe2 C5H4]Fe2 (CO) 4 (2 ) .化合物 2在加热条件下发生重排反应 ,给出硅硅键和铁铁键复分解产物 Me2 Si(η5 1 C9H6)Fe(CO) 2 SiMe2 (η5 C5H4)Fe(CO) 2 (3 ) .利用X射线衍射法 ,测定了 2和

关键词： 不对称合成   β—酮酯   微生物催化剂   金属手性催化剂   有机合成   催化氢化  

摘要： 不对称合成是当代有机合成的热点,不对称催化方法是获取单一异构手性化合物最具有前景的方法之一。本文综述了近年来用微生物和金属手性催化剂催化氢化β-酮酯的基础研究进展。

关键词： 手性膦(磷)酸酯   手性膦(磷)酰胺   不对称合成   综述  

摘要： 讨论了手性膦 (磷 )酰胺及膦 (磷 )酸酯催化剂在不对称烷基化、不对称缩合、不对称氢化、不对称氰硅化等反应中应用的最新研究进展。参考文献 4 8篇。

关键词： N-支套索冠醚   不对称合成   相转移催化剂   应用  

摘要： 综述了手性N 支套索冠醚在不对称合成中的作用 。

关键词： 过渡金属配合物   不对称合成   不对称催化   综述  

摘要： 综述了过渡金属配合物在不对称氢化、不对称环丙烷化、不对称环氧化等不对称合成中的催化应用以及最新的进展。参考文献

关键词： Ligands   Genetics   Addition reactions   Group 15 compounds   Organophosphorus compounds  

摘要： A series of organometallic reagents containing orthometalated chiral amine auxiliaries have been utilized as chiral templates to activate phospholes, vmylphosphines, and alkynylphosphines toward asymmetric ligand transformations via cycloaddition and hydroamination reactions. By a systemic manipulation of the subtle stereoelectronic properties of the auxiliaries and the metal centers, the template properties could be modified and the origins of stereoselectivity revealed. The chiral templates are able to control the disposition of selected functionalities into designated locations on the transformed P-stereogenic mono- and diphosphine ligands. This Account provides an overview of our recent work in this area.

关键词： asymmetric catalysis   amino acids   enantioselectivity   hydroamination   palladium  

摘要： We report a highly active palladium catalyst for the enantioselective conjugate addition of primary aromatic amines to N-alkenoylcarbamates, furnishing beta-amino N-Boc-amides in extremely high yields (>99%) and unprecedented optical purity (>99% ee) with just 2 mol % catalyst loading. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

关键词： HETEROCYCLIC compounds   OXYGEN   NITROGEN   NUCLEOPHILIC reactions   HYDROXY acids   ENANTIOSELECTIVE catalysis   HETEROGENEOUS catalysis  

摘要： 5H-Alkyl-2-phenyl-oxazol-4-ones 3, though differing from4H-4-alkyl-2-phenyl-oxazol-5-ones (commonly known as azlactones) only in the relative position ofoxygen and nitrogen atoms, are a greatly overlooked and underutilized class of heterocycles. We sawin them a potential class of nucleophiles that would provide easy access to α-hydroxy acids. Ourrecent success in Mo-catalyzed AAA to control diastereo- and enantioselectivity at the nucleophileusing azlactones led us to expect similar results with "oxalactims". Due to the dearth ofinformation in the literature with regards to a general synthesis of oxalactims, we decided toimplement a simple two-step process to make them, as shown in Scheme 1. α-Bromo acid halides arecondensed with benzamide in the presence of pyridine at 60 ℃ to form diamide 2. Oxalactims can thenbe obtained from cyclization of 2 in DMA containing sodium fluoride with microwave irradiation at180 ℃ in under 10 min in 44-82% yields.