关键词： 不对称合成   环氧化   手性   催化剂   烯烃  

摘要： 介绍了多类简单烯烃不对称环氧化反应的手性过渡金属配合物催化剂系统的催化效果。论述了配体结构与配合物作为环氧化反应催化剂的活性,稳定性,催化效率的关系。从配合物的电子和立体因素,几何构型与过渡态的构象和非对映异构体的能量差别探讨对不对称诱导效果的影响。同时陈述机理的研究情况。

关键词： 催化   两相催化   水溶性   氢甲酰化   不对称合成  

摘要： 本文评述了水溶性膦配体的合成及以水溶性过渡金属膦络合物为催化剂的两相催化体系的研究和开发概况，着重介绍了两相体系在烯烃氢甲酰化、不饱和化合物的加氢及催化不对称合成中的应用，并对两相催化体系研究中存在的问题进行了探讨。

关键词： pentalenolactones E and F   asymmetric synthesis   selenide elimination   Kauffmann methylenation   natural products  

摘要： A formal asymmetric synthesis of pentalenolactone E (1b) and pentalenolactone F (1a) has been accomplished. Ozonolysis of the diphenyl-substituted triquinane 3 and Kauffmann methylenation of ketone 5 with WOCl3/2 MeLi yielded the unsubstituted triquinane 9. The crucial rearrangement of the linear triquinanoid lactone 11 to the angular triquinanoid lactone 14a was accomplished using orthoformate and acid in methanol. Subjecting triquinanes 14a/b to the selenoxide method gave triquinene 15. Homologation of gamma-lactone 15 to the angular diquinanoid delta-lactone 2 via a Horner-Wadsworth-Emmons or Peterson reaction of hemiacetals 16a/b was, however, not successful. Chemoselective reduction of 14a afforded hemiacetals 21a/b, reaction of which with the phosphonate salt 17a ultimately led to the ketene dithioacetal 22. The angular intermediates 25a/b were obtained from 22 by reduction to give the linear hemiacetals 24a/b, which rearranged to the dithio ortholactones 25a/b in the presence of acid. Introduction of the double bond and deprotection were accomplished via selenation of 25a/b with N,N-diethylbenzeneselenylamide and treatment of selenides 30a/b with silver nitrate. The unsaturated aldehydes 28 and 29 thus obtained were converted to 2 and 31, respectively, by oxidation with manganese dioxide in the presence of sodium cyanide, methanol and acetic acid. Alkene 2 was isolated by crystallization.

关键词： 固态反应   溶液反应   选择性   不对称合成   有机反应  

摘要： 总结了一些典型的固态有机反应。由于固态反应的特性,多数固态有机反应表现出较溶液中更高的反应效率和更好的选择性,在某些情况下,利用光活性主体与反应物形成包结物,可实现对映选择性的不对称固态合成。

关键词： 手性配基   联二萘   光学活性药物   不对称合成   对映体过量百分率  

摘要： 综述了手性配基联二萘及其类似物在光学活性药物合成中的研究进展及应用，包括对Ｃ＝Ｃ、Ｃ＝Ｏ双键的不对称催化氢化，Ｄｉｅｌｓ－Ａｌｄｅｒ反应，Ａｄｏｌ缩合，加氢甲酰化等。

关键词： 季碳   不对称合成   天然产物   全合成   合成  

摘要： 综述了季碳的不对称构筑法及其在天然产物全合成中的应用。按照合成反应不同，分７类加以介绍。参考文献２４篇。

摘要： Chapter I provides a background to α-amino acids, e.g. examples of their biological functions and of their uses to man are given. The most notable among the methodologies for the asymmetric synthesis of α-disubstituted glycines devised by Schallkopf, Williams, Ojima and Seebach are reviewed. Chapter II elucidates the importance of the ferrocenyl moiety as oxazolidinone ring substituent for the success of the new methodology. The large scale synthesis of ferrocenecarboxaldehyde is outlined. The optimisation of the condensation of ( S )-alanine and ferrocenecarboxaldehyde and the cyclisation of the resulting imine to yield methyl-substituted cis- and trans -oxazolidonones are discussed. Chapter III gives an account of the alkylations of the methyl-substituted cis -oxazolidinone using different bases and a wide variety of alkyl halides to yield trans- alkylated oxazolidinones. The hydrolysis of the alkylated oxazolidinones to yield α-methyl α-amino acids is described. Chapter IV gives an account of the aldol reactions of the methyl-substituted cis- oxazolidinone using LDA as base with a variety of aldehydes and trapping agents to yield trans-substituted oxazolidinones. The hydrolysis of the substituted oxazolidinones to yield α-methyl α-amino β-hydroxy acids is described. Chapter V outlines the asymmetric synthesis of α,α-disubstituted glycines with substituents other than methyl. As representative examples ( S )-2-aminobutyric acid, ( S )-norvaline, ( R )-2-phenylglycine, ( S )-phenylalanine, O -benzyl-( S )-serine and ( S )-tryptophan were used as starting α-amino acids.

关键词： asymmetric amplification   asymmetric catalysis   asymmetric synthesis   autocatalysis   chiral auxiliaries  

摘要： Who would have thought before 1986 that an enantiomerically impure catalyst could give a product in an asymmetric synthesis with an enantiomeric excess higher than that of the catalyst? Until then it was assumed that the ee value of the product (ee prod ) from an asymmetric synthesis was linearly correlated to the ee value of the chiral auxiliary (ee aux )-in fact a large deviation is possible (see diagram). These nonlinear effects are not only of academic interest since they have a variety of practical uses, which are highlighted in this review.◆ (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)

摘要： Silicon based organic reagents have enjoyed a wealth of applications in the last thirty year. However, the development of organosilanes for asymmetric synthesis has been less prolific. The drawbacks of using 'Si-centred' chiral organosilanes has led to 'C- centred' organosilicon compounds being the substrate of choice. This research has been directed at the synthesis and application of C(_2) symmetric 'C-centred' cyclic organosilicon species and their potential applications in asymmetric synthesis. A variety of synthetic methods have been considered, the most successful of which has been the double asymmetric hydroboration of substituted divinylsilanes. This has allowed the use of unusual boron redistribution chemistry to give access to both acyclic and cyclic rmw-substituted organosilicon compounds with high stereoselectivity. A new method for the synthesis of dichlorosilanes from their diphenyl analogue has been developed and has been shown to occur almost instantaneously and in good yield. Finally, the application of dichlorosilacycles in tethered Diels-Alder reactions has been investigated and has been shown to give enhanced rates of reaction when compared to acyclic silicon tethers.

关键词： HIGHER-ORDER CYCLOADDITION   ENOL ETHER   ORGANIC-SYNTHESIS   AUXILIARY   CYCLOPROPANATION   OXIDATION  

摘要： Optically active tropilidenes were prepared by cycloaddition of a diazo ester to an aromatic ring using 2,4-pentanediol as a chiral linking bridge under complete regio- and stereo-differentiations.