关键词： alkylation   amino acids   ammonium salts   asymmetric synthesis   C-C bond formation   organic catalysis   phase-transfer catalysis  

摘要： Cinchonidine, epicinchonidine, cinchonine or quinine have been N-anchored to cross-linked polystyrene (Merrifield resin) or grafted polystyrene (Syn-Phase(TM) Lanterns) affording polymer-supported chiral ammonium salts which are employed as phase-transfer catalysts in the asymmetric alkylation of N-(diphenylmethylene)glycine esters. These new polymeric catalysts can be easily recovered after the reaction by simple filtration and reused.

关键词： STEREOCHEMISTRY   QUINOLINE   ESTERS   BENZOPYRANS   METAL bonding   HETEROCYCLIC compounds  

摘要： To establish the synthetic utility of palladacycles, a stable racemic benzannulated azapalladacycle featuring a palladium-bonded sp(3)-hybridized stereogenic carbon was prepared and converted into a series of racemic 2,3,4-trisubstituted 1,2-dihydroquinolines via a regioselective insertion of activated alkynes (RCdropCCOOEt). Analogous diastereomerically enriched azapalladacyle (92% de) and oxapalladacycle (64% de) were synthesized from arylpalladium(II) iodo complexes possessing a nonracemic spectator ligand ((1R,2R)-N,N,N',N'-tetramethyl-1,2-diaminocyclohexane) via an intramolecular displacement of the iodide by an ester enolate. Absolute configurations of the metal-bonded stereocenters in the diastereomerically enriched palladacycles were unequivocally assigned, and the efficiency of stereoinduction was systematically studied. On the basis of these experiments, a plausible mechanism for the transfer of chirality from the nonracemic auxiliary ligand to the palladium-bonded stereogenic carbon was proposed. A restricted rotation about the palladium-aryl bond in arylpalladium(II) iodo complexes giving rise to atropisomers, as well as the nature of the leaving group (iodide or acetate), were found to play a crucial role in the chirality transfer process. Diastereomerically enriched palladacycles underwent a ligand exchange with triphenylphosphine followed by regioselective insertion of unsymmetrical alkynes to afford nonracemic 1,2-dihydroquinolines (six examples) in excellent 80-91% ee and 2H-1-benzopyrans (four examples) in 32-56% ee.

关键词： Amides   Catalysts   Nitrogen   Organic compounds   Molecular structure  

摘要： Phase-transfer-catalyzed direct Mannich reaction of glycinate Schiff base 3 with alpha-imino ester 4 has been accomplished with high enantioselectivity by the utilization of N-spiro C-2-symmetric chiral quaternary ammonium bromide 2 as a catalyst. This methodology enables the catalytic asymmetric synthesis of differentially protected 3-aminoaspartate, a nitrogen analogue of dialkyl tartrate. The product (syn-5) was converted into a precursor (6) of streptolidine lactam.

关键词： Coupling reactions   Adducts   Reaction products   Aldol reactions   Enantioselective synthesis  

摘要： Three asymmetric pathways to the kavalactones have been developed. The first method is chiral auxiliary-based and utilizes aldol reactions of N-acetyl thiazolidinethiones followed by a malonate displacement/decarboxylation reaction. The second approach uses the asymmetric catalytic Mukaiyama additions of dienolate nucleophile equivalents developed by Carreira and Sato. Finally, tin-substituted intermediates, prepared by either of these routes, can serve as advanced general precursors of kavalactone derivatives via Pd(0)-catalyzed Stille couplings with aryl halides.

关键词： .diastereoselective   carbanion   nucleophiles   asymmetric synthesis   tetrahydroisoquinoline   stereochemical   enantioselective synthesis   stereogenic   Addition of carbon   Synthetic methods   synthetic strategies   Chem ReV   Isoquinoline Derivatives   Pictet-Spengler   Cyclization/Reduction   CR Connectivity  

摘要： Recent methods of the asymmetric synthesis of isoquinoline alkaloids arebased generally on two synthetic strategies:the stereochemical modification of thetraditional,classical methods (the sequential Bischler-Napieralski cyclization/reduction,thePic-tet-Spengler,various Pomeranz-Fritsch cycliza-tions) and introduction of nucleophilic orelectrophilic carbon units into the C-l position of isoquinoline derivatives (the C_1-C_(alpha)connectivity approach).

关键词： CATALYSTS   COPPER   CARBENES (Methylene compounds)   HYDROGEN bonding   ESTERS   CHIRALITY  

摘要： The reaction pathway and the mechanism of asymmetric induction in the synthesis of (+)-trans-(1R,3R)-chrysanthemic acid methyl ester from methyl diazoacetate and 2,5-dimethyl-2,4-hexadiene in the presence of a C-1-chiral salicylaldimine Cu(I) complex has been probed with the aid of hybrid density functional calculations. The key finding is that the alkoxycarbonyl carbene complex intermediate is intrinsically chiral and that the intramolecular hydrogen bonding in the carbene complex transmits the chirality information from the side chain to the carbene complex. Molecular orbital backgrounds of the structure of the carbene complex and the transition state of the cyclopropanation have been elucidated.

关键词： 含三氟甲基合成子   不对称合成   Macrosphelide A   含氟氨基酸  

摘要： 含三氟甲基合成子是合成各种含三氟甲基化合物的基石.发展廉价、易得和用途广泛的含三氟甲基合成子一直是有机氟化学的重要研究方向.本论文从廉价易得的原料出发合成了含三氟甲基合成子,并成功地将手性引入含三氟甲基合成子,然后将其运用于合成含三氟甲基生理活性化合物.全文分为以下三部分:第一部分:首先从2-溴-3,3,3-三氟丙烯出发合成了4,4,4-三氟丁炔醇2、(Z)-3-碘-3-三氟甲基烯丙醇3和(Z)-2-碘-3-三氟甲基烯丙醇4,然后研究了这些含三氟甲基合成子在钯催化下发生的环羰基化反应.对于叔醇底物可以顺利的发生环羰基化反应从而合成了一系列三氟甲基取代的2(5H)-呋喃酮类化合物、β-丁内酯类化合物及环碳酸酯类化合物;对于仲醇底物由于按照不同于叔醇底物的机理进行反应而不能得到环羰基化产物.第二部分:从丙炔醇出发高度立体选择性的合成了三氟甲基取代的反式烯烃22,然后通过Sharpless不对称双羟化成功地构建手性中心,高度立体选择性地得到了含三氟甲基的手性二醇化合物25a和25b.将手性二醇化合物转化为环硫酸酯,利用其选择性地开环实现地对手性二醇化合物高度区域和立体选择性地转化,从而得到一系列的含三氟甲基手性合成子31.从这些含三氟甲基手性合成子出发,通过区域和立体选择性地转化分别不对称地合成了anti-4,4,4-三氟苏氨酸、4,4,4-三氟丁氨酸、syn-β-三氟甲基-半胱氨酸和syn-4,4,4-三氟异苏氨酸的两个对映异构体,为高度立体选择性地合成这些含氟氨基酸提供了一系列简便有效的方法.第三部分:对具有抗细胞凝聚和抗肿瘤活性的海洋天然产物Macrosphelide A的三氟甲基衍生物的全合成研究.从含三氟甲基手性合成子25a出发通过对保护基的选择,经过多步转化分别高效地合成了Macrosphelide A的三个片段74、80和81.然后成功地对三个片段进行了连接得到了关环前体86,最后对86的关大环反应作了初步的研究.

关键词： ORGANOSULFUR compounds   IONS   PALLADIUM   CATALYSIS   ASYMMETRY (Chemistry)   ORGANIC compounds   ORGANIC synthesis (Chemistry)  

摘要： The palladium-catalyzed allylic alkylation of KSAc and KSBz with racemic cyclic and acyclic allylic esters by using N,N'-(1R,2R)-1,2-cyclohexandiylbis[2-(diphenylphosphino)-benzamide] as ligand frequently gave the corresponding allylic thioesters with high ee values and yields. The reaction of the cyclic allylic carbonates with KSAc in the presence of H2O was accompanied by a partial palladium-catalyzed enantioselective "hydrolysis" of the substrates with formation of the corresponding enantioenriched allylic alcohols. The degree of the "hydrolysis" was strongly dependent on the solvent and the thiocarboxylate ion. Highly selective kinetic resolutions (KRs) were observed in the palladium-catalyzed reaction of the racemic cyclohexenyl and cycloheptenyl acetates with KSAc. While the KR of the cyclohexenyl acetate is characterized by a selectivity factor S = 72 +/- 19, that of the cycloheptenyl acetate afforded (R)-cycloheptenyl acetate of greater than or equal to99% ee in 48% yield and (S)-cycloheptenyl thioacetate of 98% ee in 50% yield. The palladium-catalyzed reaction of the racemic cyclopentenyl acetate with KSAc showed a strong "memory effect" (ME), that is, both enantiomers reacted with different enantioselectivities. The ME was probed by studying the palladium-catalyzed reactions of both the matched acetate of greater than or equal to99% ee and the mismatched acetate of greater than or equal to99% ee with KSAc. The acetates not only reacted with different enantioselectivities and rates but also suffered an unexpected and concomitant palladium-catalyzed racemization in the presence of the chiral ligand. This led in the case of the mismatched acetate to a temporary dynamic kinetic resolution (DKR) that featured a racemization of the mismatched acetate by the chiral catalyst. Studies of the palladium-catalyzed reaction of the racemic cyclopentenyl acetate, carbonate, and naphthoate with KSAc in the presence of the chiral ligand also showed the ME to be strongly de

关键词： METHYL ether   ASYMMETRIC synthesis   ASYMMETRY (Chemistry)   LIGNANS   RING formation (Chemistry)   PHOTOCHEMISTRY  

摘要： A short, efficient synthesis of the lignan (+)-lyoniresinol dimethyl ether is described. The synthesis is achieved by asymmetric photocyclization of an achiral dibenzylidenesuccinate to a chiral aryldihydronaphthalene. (-)-Ephedrine is used as a chiral auxiliary to bias the atropisomeric equilibrium in the dibenzylidenesuccinate prior to the photochemical reaction. The synthesis of the title compound was accomplished in five steps, and the final product was recrystallized to constant melting point and rotation.

关键词： ORGANIC acids   ORGANIC synthesis (Chemistry)   LACTONES   CINNAMATES   HYDROGEN chloride   CATALYSIS  

摘要： A novel and practical asymmetric synthesis of chiral glycidic acid derivatives involving methyl (2R,3S)-3-(4-methoxyphenyl)glycidate ((2R,3S)-2a), a key intermediate for diltiazem hydrochloride (1), was developed. Treatment of methyl (E)-4-methoxycinnamate ((E)-3a) with chiral dioxirane, generated in situ from a catalytic amount (5 mol %) of an 11-membered C-2-symmetric binaphthyl ketone (R)-7a, provided (2R,3S)-2a in 92% yield and 80% ee. Other cinnamic acid esters and amides were epoxidized by the use of the same procedure to give the corresponding chiral glycidic acid derivatives with up to 95% yield and 92% ee. Higher enantioselectivities in the asymmetric epoxidation of (E)-cinnamates than that of (E)-stilbene derivatives were observed and were proposed to be attributed to a dipole-dipole repulsion between oxygen atoms of an ester group in the cinnamates and those of the lactone moieties in the binaphthyl dioxirane.