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系列手性氮杂小环配体的合成及在不对称催化反应中的应用研究

Synthesis of Chiral Nitrogen Heterocycle-based Ligands and Their Applications in Asymmetric Catalysis

【作者】 牛俊龙

【导师】 宋毛平;

【作者基本信息】 郑州大学 , 有机化学, 2009, 博士

【摘要】 本论文利用易得的L-氨基酸和手性苯乙胺为手性源,设计合成了两类三员氮杂环手性氨基醇配体,两类四员氮杂环手性氨基醇配体以及三类三员氮杂环手性硫醚配体。考察了它们在不对称催化反应中的催化活性,提出了配体在相关不对称催化反应中可能的机理。本论文主要集中在以下五个方面:1)通过苯乙炔和苯乙酰氯热解、间苯基萘酚的偶联、鹰爪豆碱的拆分得到光学纯的联萘酚(S)-VANOL(3),并对其他两种包结物拆分法进行了初步的研究。以(S)-VANOL-B(OPh)3为催化剂,通过氮杂环丙烷化反应,然后与格式试剂或四氢锂铝分别反应得手性配体7a,7b,并且考察了该催化剂在二茂铁亚胺的氮杂环丙烷化反应中的应用,取得34%产率和62%ee值。同时也考察了配体(S)-VANOL(3)和7a,7b在二乙基锌对醛的不对称加成反应中的催化活性。2)以易得的L-丝氨酸为原料,经过酯化、保护、关环、格氏试剂反应、脱保护,最后与1-二茂铁基乙酸酯反应得一对非对映异构体12,通过TLC分离得光学纯配体(S,2S)-12和(R,2S)-12,利用X-光衍射确定了配体中新产生的中心手性的构型。研究了手性配体12在二乙基锌与芳香醛不对称加成反应中的催化活性,最好结果取得了99%的化学产率和99%的ee值。结合试验结果和配体的晶体结构,提出了手性配体在不对称乙基化反应中可能的反应机理。3)通过手性苯乙胺与2,4-二溴丁酸甲酯关环,最后与格式试剂反应并通过TLC分离得手性配体15和17。通过(R,2S)-17的晶体结构,确定了配体中新产生的中心手性的构型。研究了手性配体15和17在炔基锌与芳香醛不对称加成反应中的催化活性,取得了49-84%的收率和69-84%ee值。同时结合试验结果和配体的晶体结构,提出了配体在该不对称催化反应中可能的反应机理。4)以易得的(R)-半胱氨酸和L-甲硫氨酸为原料,合成了具有不同螯合链和电子效应的手性N,S-双齿三员氮杂环硫醚配体20a-c,23和25a-c。研究了手性配体在钯催化的不对称烯丙基取代反应中的催化活性,其中配体20b取得了99%的化学产率和91%的ee值。5)配体20a,20b和23分别与1,3-二苯基烯丙基氯化钯二聚物在AgSbF6作用下得配体的π-烯丙基钯络合物中间体26,27和28。通过对固体的X-单晶衍射以及溶液的NMR[1H NMR,13C NMR,dept,1H-1H COSY, 13C-1H correlation(HSQC,HMBC)]和NOE(2D-NOESY,NOE difference)分析,首次系统地阐述了S-N(sp3)类配体在钯催化的不对称烯丙基取代反应中配体的结构对反应对映选择性的影响。关

【Abstract】 With this context, two kinds of chiral aziridine-based amino alcohol ligands, twokinds of chiral azetidine-based amino alcohol ligands and three kinds of aziridinesulfide ligands have been explored by use of readily available L-amino acids, (S)- or(R)-phenylethylamine. Moreover, we examined their catalytic activities in relatedasymmetric reactions. Possible mechanism for the related asymmetric induction wasproposed on the basis of results of reactions and the crystal structures of ligands.This dissertation mainly focuses on 5 aspects as follows:1) The optically pure (S)-VANOL (3) was prepared by the thermolysis of phenlacetylchloride in the presence of phenylacethlene, the coupling of the 3-phenyl-1-naphthol,the deracemization of VANOL with the in situ generation of copper(Ⅱ) in thepresence of (-)-spartiene. Two other methods for the deracemization of racemate 2involving the reactions of salt formation were also tested. Ligands 5a-e were preparedfrom the asymmetric catalytic aziridination reaction with chiral catalysts preparedfrom triphenylborate and (S)-VANOL 3, and then converted into the correspondingcarbinols (7a, 7b) by reaction with PhMgBr or LiAlH4. The catalyst(VANOL-B(OPh)3) gave low induction (34% yield and 60% ee) for the addition ofethyl diazoacetate to N-ferrocenylmethyl imine. Their catalytic activities wereexamined in the asymmetric addition of diethylzinc to benzaldehyde as a modelreaction. 2) Chiral ligands 11 was prepared from easily available L-serine by the esterification,Trt-protection, cyclization, treatment with PhMgBr, deprotection, and then reactedwith rac-1-ferrocenylethyl acetate to yield a chromatographically separablediastereomeric mixture of (S, 25)- and (R, 2S)-12 with almost 1:1 ratio. Thestereochemical configuration of the ligand 12 was established by X-ray analysis. Thereaction of diethylzinc with arylaldehydes gave the corresponding alcohols in up to99% chemical yields and 99% ee. A possible mechanism for this asymmetricalkynylation of aldehydes was also proposed.3) Methyl 2,4-dibromobutanoate 13 was reacted with (S)- or (R)-phenylethylamine toyield a mixture of diastereomeric N-alkylazetidine esters (14, 16). These esters wereseparated by the preparative silica gel TLC plate in optically pure form, and thenconverted into the corresponding carbinols by reaction with PhMgBr. The X-raystructure analysis of ligand (R, 25)-17 established the stereochemical configuration atC-2 relatively to the known (R)-configuration of theα-methylbenzyl group. Theircatalytic capabilities in the asymmetreic addition of alkynylzinc to aldehydes were examined with moderate-to-good enantioselectivities. A possible mechanism for thisasymmetric alkynylation of aldehydes was also proposed.4) A series of new chiral heterobidentate azieidine-based ligands 20a-c, 23 and 25a-chaving different chelating size and electric effect were readily prepared from cheapand easily available (R)-cysteine and L-(+)-methionine. A Pd-catalyzed asymmetricallylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate was usedas a model reaction to examine the catalytic efficiencies of these aziridine sulfideligands, and ligand 20b afforded the enantioselectivity of up to 91% ee. 5) The palladium allylic complexes 26, 27, and 28 were prepared from thebis[(μ-chloro)(η3-1,3-diphenylallyl)palladium(Ⅱ)] and ligands 20a, 20b, and 23,respectively, in the presence of AgSbF6. The origin of the pattern of enantioselectivityfor heterobidentate sulfide-tertiary amine (sp3) ligands was first rationalized by theX-ray diffraction and solution NMR [1H NMR, 13C NMR, dept, 1H-1H COSY, 13C-1Hcorrelation (HSQC, HMBC)] and NOE (2D-NOESY, NOE difference) studies of theintermediate palladium-π-complex.

  • 【网络出版投稿人】 郑州大学
  • 【网络出版年期】2011年 10期
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