关键词： 钛试剂   RTiX3   反应选择性   羰基化合物   醛酮   有机金属   不对称诱导   对映体过量   不对称合成   亲核性  

摘要： RMgX、RLi和RZnX等有机金属试剂在合成中的广泛应用已为人们熟知,由于这些试剂碱性强活性高,往往不适于某些醛酮的加成,且反应选择性不太理想。近十年来,Seebach和Reetz等人深入研究了RTiX₃类型有机钛试剂。在RTiX₃中,R为烃基、OR、OAr等,x可为卤素、OR、NR₂¹ 等不同基团。通过对配体X的改变,可以对电子因素和空间因素两个方面进行广泛的调节,从而使RTiX₃试剂在醛酮的加成反应中具有高度的化学选择性、对映选择性和立体选择性。所以,RTiX₃试剂现已成为有机合成中的有力工具。

关键词： α-甲基   α-氨基酸   卡宾   不对称合成   相转移催化  

摘要： 本文报道了以N—苄基氯化辛可宁为手性催化剂,由相转移卡宾法来不对称合成α—甲基—α—氨基酸.探讨反应条件对化学产率和光学收率的影响.

关键词： .asymmetric synthesis   stereospecific   deuterium   lithio   tin compounds   dichloromethyl   tertiary alcohols   diastereoselection   pinanediol   diastereomeric ratio   Cp symmetry   chloro boronic ester  

摘要： The reaction of chiral diol boronic esters with (dichloromethyl)lithium to form diol alpha-chloro boronic esters in high diastereomeric purity has been improved by the use of diols of C2 symmetry. Reaction of the resulting alpha-chloro boronic esters with alkyl Grignard reagents provides a further kinetic resolution in which the minor isomer is not converted to diastereomer but to an air-sensitive borinic ester. The final diastereomeric ratio can exceed 1000:1, and a diastereomeric pair of insect pheromones has been synthesized in unusually high purity. Other recent applications of alpha-chloro boronic ester chemistry in asymmetric synthesis will also be discussed. Diol boronic esters of C2 symmetry are useful in the conversion of alpha-chloro boronic esters via alpha-alkoxy tin compounds to alpha-lithio ethers, which in turn can be coupled to alpha-chloro boronic esters to provide a stereospecific convergent coupling of two chiral carbon chains. New applications of the older pinanediol ester technology have also been explored. These include syntheses of phenylalanine and of glycerol bearing stereospecific deuterium labels. Preparations of chiral tertiary alcohols have given useful stereoselectivity with some structures and not with others. A supplementary discovery is that solvent free dichloroborane can be generated from boron trichloride and trialkylsilanes and is an efficient hydroborating agent.

关键词： .asymmetric synthesis   asymmetric hydroboration   allylboration   organoboranes   asymmetric reduction   purities   crotylboration   boron approach  

摘要： The unique chemistry of organoboranes has made possible a three-pronged approach to asymmetric synthesis: 1) asymmetric hydroboration, 2) asymmetric reduction, and 3) asymmetric allyl- and crotylboration. Consequently, boron chemistry makes possible not only a uniquely general synthesis of pure enantiomers (with purities approaching 100% ee) as well as more complex stereoisomers by processes that are simple and broadly applicable. Boron derived reagents have proven to be exceptionally versatile for the asymmetric reduction of the carbonyl group in a variety of derivatives to give products of optical purities approaching 100% ee. Finally, the synthesis of chiral organoboranes containing allyl, crotyl and related groups attached to boron is providing a highly valuable synthesis via allylboration of stereoisomers in purities approaching 100% ee. It is evident that boron chemistry is providing major new routes for asymmetric synthesis in organic chemistry.

关键词： 谷蠹   不对称环氧化   集结信息素  

摘要： 谷蠹(Rhyzopertha dominica)是世界性储藏产物的主要害虫、在我国仓库中破坏性也占首位.1981年Williams等人首次鉴定和合成了这种信息素.它的两个活性组分是(E)-2-甲基-2-戊烯酸(S)-(+)-1-甲基丁基酯1和(E)-2,4-二甲基-2-戊烯酸(S)-(+)-1-甲基丁基酯2. Williams等人从自然界光学活性体——谷氨酸为原料,经过八步合成1或2,在合成过程中用了剧毒试剂氢化钠.本文报道的不对称合成主要应用Sharpless环氧化动力学拆分以及Wittig反应,以易得的巴豆醛为原料,经过四步得目的化合物,总得率30％。

关键词： 不对称合成   樟脑   亚胺   烷基化  

摘要： 目前,不对称合成光学活性化合物取得了较大进展,不对称合成α-氨基酸、β-氨基醇、α-取代苄胺的报道很多。但是,不对称合成生物碱类物质——α-取代氨甲基吡啶类化合物还未见文献报道,而此类化合物有潜在的应用前景。为此,我们以(+)

关键词： 樟脑   衍生物   不对称合成   手性助剂  

摘要： 介绍了樟脑及其衍生物在不对称还原反应、加成反应、烷基化反应、Diels-Alder 反应、氧化反应和卤化反应中的应用。同时还列举了樟脑及其衍生物在不对称合成中用作手性试剂和手性催化剂的一些例子。

摘要： The asymmetric synthesis of a fully protected version of calyculin A, a tumor promoter isolated from Discodermia calyx, is described. A flexible approach allowed for the synthesis of 109 from aldehyde 103 and phosphonium salt 108 by a Wittig reaction. Ten of the fifteen stereogenic centers were established by auxiliary-controlled asymmetric induction. The tetraene portion was addressed with a combination of Horner-Emmons and Stille coupling chemistry, and the substituted oxazole moiety was obtained by an oxidative ring synthesis sequence.(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) Methods for phosphorylation of the C$\sb{17}$ hydroxyl group and removal of the protecting groups are presented, and the ongoing program to complete the total synthesis of the natural product is described.

摘要： The aim of the work described in this thesis is the investigation of iron acyl complexes for organic synthesis. The phenomena of double asymmetric induction is also investigated. Chapter 1 is an introduction to the synthesis of homochiral compounds. The synthesis of homochiral <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-hydroxy carbonyl compounds is explored in more detail and the iron chiral auxiliary [(C_5H_5)Fe(CO)(PPh_3)] is introduced. Chapter 2 details the use of iron acyl complexes for the synthesis of homochiral <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-lactones. Under anhydrous conditions, the formation of <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-lactones via the oxidative decomplexation of <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-hydroxy iron acyl complexes is described. Chapter 3 describes the synthesis of tetrahydrolipstatin, with an account of previous syntheses being given. An asymmetric synthesis of tetrahydrolipstatin using the iron chiral auxiliary [(C 5 H 5 )Fe(CO)(PPh 3 )] in the key carbon-carbon bond forming reaction, as well as formation of the <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-lactone moiety, is given. A formal synthesis of tetrahydrolipstatin is also described, where the double asymmetric induction between protected <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-hydroxy aldehydes and iron acyl complexes is investigated. Chapter 4 describes an asymmetric synthesis of valilactone, with a similar route to that developed in chapter 3 for the synthesis of tetrahydrolipstatin being used. Chapter 5 describes investigations into the reaction between iron acyl complexes and homochiral aldehydes and ketones. The double asymmetric induction between homochiral, <IMG WIDTH=9 HEIGHT=24 ALIGN=MIDDLE SRC="/maths/***">-hydroxy aldehydes and <IMG WIDTH=7 HEIGHT=7 ALIGN=BOTTOM SRC="/maths/***">-methy

关键词： .substituents   Valerolactones   asymmetric ring   glutaric   anhydrides   simple alkyl  

摘要： In organic solvents, lipase Amano P catalyzed the asymmetric ring opening of glutaric anhydrides bearing-CH2Cl,-CH2F and -OCH3 groups at position 3 with methanol and 1-butanol to afford the corresponding mono esters in 70-86% e.e. Optically active sigma-valerolactones were synthesized from the mono esters in overall yields of 34-62%. The R-configuration was assigned to the mono esters and the lactones by means of a CD analysis and chemical correlation. This indicates that the lipase preferentially attacked the pro-R carbonyl group of these anhydrides carrying hetero atoms, in keeping with the trend observed for glutaric anhydrides having simple alkyl substituents.