共查询到20条相似文献,搜索用时 500 毫秒
1.
This communication outlines the development of a novel, general synthetic route to substituted α-tetralones 5 , their subsequent conversion to the α,β-unsaturated ketones 11 , and an improved, one-step transformation of 11 to the tricyclic title compounds 1. Thus, substituted derivatives of 1 can be prepared in six steps from simple benzaldehydes, or, in three steps from more readily available α-tetralones. 相似文献
2.
Samuel S. Libendi 《Tetrahedron》2008,64(18):3935-3942
N-Protecting groups of α-substituted cyclic amines strongly affected the regioselectivity in electrochemical methoxylation of these compounds. Namely, N-acyl derivatives were transformed into α′-methoxylated compounds, while N-cyano derivatives changed into α-methoxylated derivatives. Furthermore, Lewis acid catalyzed nucleophilic substitution of the α-methoxylated compounds protected with cyano group afforded α,α-disubstituted cyclic amines. 相似文献
3.
《Tetrahedron: Asymmetry》2006,17(10):1465-1492
Enantioselective organocatalytic processes have reached maturity in recent years with an impressive number of applications now available. The application of these advantageous methodologies to the construction of chiral α-hetereofunctionalised carbonyl compounds allows us to obtain important chiral building blocks, such as α-amino acids, α-amino alcohols, aziridines, epoxides, 1,2-diols and α-sulfenylated, selenenylated and halogenated carbonyl derivatives. Proline, imidazolidinone derivatives, cinchona alkaloids and their ammonium salts, as well as Brønsted acid derivatives, have been used as chiral catalysts for these purposes. A survey of contributions in this field will be discussed throughout this review. 相似文献
4.
Dr. Sheng Guo Jiaqi Zhu Prof. Dr. Stephen L. Buchwald 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21027-21031
A Cu-catalyzed enantioselective hydroamination of α,β-unsaturated carbonyl compounds for the synthesis of β-amino acid derivatives was achieved through ligand-controlled reversal of the hydrocupration regioselectivity. While the hydrocupration of α,β-unsaturated carbonyl compounds to form α-cuprated species has been extensively investigated, we report herein that, in the presence of an appropriate ancillary chiral ligand, the opposite regiochemistry can be observed for cinnamic acid derivatives, leading to the delivery of the copper to the β-position. This copper can react with an electrophilic aminating reagent, 1,2-benzisoxazole, to provide enantioenriched β-amino acid derivatives, which are important building blocks for the synthesis of natural products and bioactive small molecules. 相似文献
5.
The α-ferrocenylalkyl caebenium ions are formed from ferrocene and carbonyl compounds in strongly acidic media, in particular mixtures of fluorosulfuric acid and trichloroacetic acid. The α-ferrocenylalkyl carbenium ions are scavenged by nucleophiles or bases. The addition of nucleophiles produces the corresponding α-substituted ferrocenyl alkanes. Proton abstraction by base from the β-position leads to the ferrocenylethene derivatives.Such electrophilic substitutions of ferrocene by carbonyl compounds, followed by suitable scavengeing of the α-ferrocenylalkyl carbenium ion, form the basis of one-pot syntheses of various ferrocene derivatives. 相似文献
6.
《Analytical letters》2012,45(14):919-927
Abstract A specific, sensitive and relatively simple procedure is described for the quantitative analysis of benzilic acid. The method is based on α-naphthofuchsone formation obtained by condensation of benzilic acid with α-naphthol in the presence of concentrated sulfuric acid and measuring the resultant hydroxytriaryl methyl cation at 558 mμ. No interference was observed with other glycolic acid derivatives or oxygen-bearing compounds. As little as 5 × 10?6 M benzilic acid is determinable. 相似文献
7.
Catalytic Asymmetric 1,2‐Addition of α‐Isothiocyanato Phosphonates: Synthesis of Chiral β‐Hydroxy‐ or β‐Amino‐Substituted α‐Amino Phosphonic Acid Derivatives
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yi‐Ming Cao Fang‐Fang Shen Fu‐Ting Zhang Jin‐Long Zhang Prof. Dr. Rui Wang 《Angewandte Chemie (International ed. in English)》2014,53(7):1862-1866
α‐Amino phosphonic acid derivatives are considered to be the most important structural analogues of α‐amino acids and have a very wide range of applications. However, approaches for the catalytic asymmetric synthesis of such useful compounds are very limited. In this work, simple, efficient, and versatile organocatalytic asymmetric 1,2‐addition reactions of α‐isothiocyanato phosphonate were developed. Through these processes, derivatives of β‐hydroxy‐α‐amino phosphonic acid and α,β‐diamino phosphonic acid, as well as highly functionalized phosphonate‐substituted spirooxindole, can be efficiently constructed (up to 99 % yield, d.r. >20:1, and >99 % ee). This novel method provides a new route for the enantioselective functionalization of α‐phosphonic acid derivatives. 相似文献
8.
Oxonium ylide intermediates generated fromα-diazocarbonyl compounds and water were trapped by Zn(Ⅱ)-activatedα-dicarbonyl compounds.The reaction gaveα,β-dihydroxyl acid derivatives in moderate yield. 相似文献
9.
Mass spectrometric investigations of α,δ diols and their halogenated derivatives revealed the necessity of postulating a mechanism for both their elimination of water and of haloid acid. This mechanism proceeding via a transition state of larger ring-size than described for similar monofunctional aliphatic compounds was confirmed by deuterium labelling. 相似文献
10.
Dr. Kostiantyn O. Marichev Kan Wang Nicole Greco Kuiyong Dong Jinzhou Chen Prof. Dr. Jinping Lei Prof. Dr. Michael P. Doyle 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):340-347
1,2,3-Trisubstituted donor–acceptor cyclopropenes (DACPs) generated in situ from enoldiazo compounds react with nucleophiles to form α-substituted succinic acid derivatives in high yields. Initial dirhodium(II) carboxylate catalysis rapidly converts enoldiazo-acetates or -acetamides to DACPs that undergo catalyst-free Favorskii ring opening with amines, and also with anilines, alcohols, and thiols, when facilitated by catalytic amounts of 4-dimethylaminopyridine (DMAP). This methodology provides easy access to mixed esters and amides of monosubstituted succinic acids, including derivatives of naturally occurring compounds. It also affords dihydrazide, dihydroxamic acid, and diamide derivatives, as well as α-substituted tetrahydropyridazine-3,6-diones in high yields. Attempts to generate optically enriched DACPs were not successful because their populations having the R and S configurations formed with a chiral dirhodium catalyst are quite similar, and the loss of enantiocontrol likely originates from the DACP ring forming step which is reversible with its intermediate metal carbene. 相似文献
11.
Various β-alkylthio acid derivatives were prepared conveniently from thioacetates and α,β-unsaturated compounds through borohydride exchange resin (BER)-Pd catalyzed transesterification of thioacetates to the corresponding thiols and Michael addition of the resulting thiols to α,β-unsaturated compounds. 相似文献
12.
An efficient and generally applicable method for stepwise α-alkylatton of esters, nitriles, and ketones via the α-tert-butylthio derivatives is described. The method involves reductive-protonation and reductive-alkylation of α-alkylthio α,α-bis-alkylated carbonyl compounds which are prepared by stepwise alkylation of the corresponding simple α-alkylthio carbonyl precursors. The reduction is conveniently performed by use of stoichiometric amounts of a dissolving metal, particularly lithium, affording correspondingly the α-mono-and the α,α-bis-alkylated carbonyl compounds in good yields. 相似文献
13.
Prof. Dr. Kazuaki Ishihara Kazuki Nishimura Katsuya Yamakawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17794-17800
Catalytic enantioselective α-fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α-fluorinated carbonyl compounds. Nevertheless, α-fluorination of α-nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α-hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3-(2-naphthyl)-l -alanine-derived amides are highly effective catalysts for the enantio- and site-selective α-fluorination of N-(α-arylacetyl) and N-(α-alkylacetyl) 3,5-dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α-fluorinated α-amino acid derivative). α-Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield. 相似文献
14.
Eiji Tayama Ryota Sato Keisuke Takedachi Hajime Iwamoto Eietsu Hasegawa 《Tetrahedron》2012,68(24):4710-4718
Selective amine de-alkylation enables the conversion of Sommelet–Hauser rearrangement products into 2-aryl-2-bromoacetic acid derivatives. These compounds are valuable synthetic intermediates in the synthesis of α-aryl-α-amino or α-aryl-β-amino acid derivatives. The method presented herein is a formal de-N,N-dialkylation of Sommelet–Hauser rearrangement products. 相似文献
15.
GUAN Jing-Qu HU Zun-Ju ZOU Zhi-Chen WU Zhi-GuangDepartment of Chemistry Shandong Teachers'''' University Jinan Shandong China Institute of Photographic Chemistry Chinese Academy of Sciences Beijing China 《中国化学》1997,15(4):366-370
Ten aromatic derivatives of β-aminopropionic acid and γ-aminobutyric acid were prepared.Their compositions and structures were identified by elemental analysis,IR,and 1H NMR.They have been examined for their antibacterial action against Staphylococcua aurens and Escherichia coli.These compounds showed higher activity than the aromatic derivatives of ct-amino acid which were reported previously.The general conclusion to be drawn is that the distance between amino and carboxylic group in these molecules could affect their antibacterial activity.Furthermore,those compounds with p-methyl substituent in phenyl ring exhibit higher activity than the others,and all the compounds exhibit higher activity against Escherichia coli and against Staphylococcua aureus. 相似文献
16.
T. A. Mastryukova 《Heteroatom Chemistry》1991,2(1):141-150
The addition of Schiff bases of α-aminoacid esters to vinylphosphoryl compounds was studied as a method for the synthesis of phosphinothricin and its analogues. The reaction was found to proceed smoothly in DMSO in the presence of strong nitrogen bases and under the conditions of phase transfer catalysis. The Claisen condensation of β-phosphorylated propionitrile with diethyl oxalate was studied; phosphorylated derivatives of hydroxycitraconic acid nitrile were prepared on hydrolysis; transformation of such a derivative into a cyclic imide as well as into trimethylsilyl esters of these acids and their Z → E transformation were investigated. Cyclization reactions between α,ω-dibromoalkanes and phosphoryl compounds containing an active methylene group affording cyclopropane and other cyclic derivatives were studied. The cyclopropane ring is cleaved by amines to give aminophosphinocarboxylic acids. 相似文献
17.
Dr. Minghao Feng Roberto Tinelli Ricardo Meyrelles Prof. Dr. Leticia González Dr. Boris Maryasin Prof. Dr. Nuno Maulide 《Angewandte Chemie (International ed. in English)》2023,62(1):e202212399
α-Amino acid derivatives are key components of the molecules of life. The synthesis of α-amino carbonyl/carboxyl compounds is a contemporary challenge in organic synthesis. Herein, we report a practical method for the preparation of α-amino acid derivatives via direct hydrative amination of activated alkynes under mild conditions, relying on sulfinamides as the nitrogen source. Computational studies suggest that the reaction is enabled by a new type of sulfonium [2,3]-sigmatropic rearrangement. 相似文献
18.
采用高效液相色谱法,以9-蒽醛为衍生试剂,在5种多糖衍生物的手性固定相(CSPs)上对几种α-氨基酸甲酯对映体进行了手性分离。色谱条件如下: 流动相为含3%~10%(v/v)异丙醇的正己烷溶液,流速为1.0 mL/min,检测波长为254 nm。结果表明,α-氨基酸甲酯-9-蒽醛亚胺衍生物在Chiralcel OD柱或Chiralcel OD-H柱上的手性分离结果优于其他CSPs,而且在Chiralcel OD柱或Chiralcel OD-H柱上全部得到了基线拆分(α=1.24~5.47, Rs=2.56~13.90), L-对映体在这两种色谱柱上的保留强于D-对映体。同时还考察了几种脂肪胺在5种多糖衍生物手性固定相上的对映体拆分效果,结果表明脂肪胺的9-蒽醛亚胺衍生物在Chiralcel OD柱或Chiralcel OD-H柱上的分离效果良好。该法可用于其他α-氨基酸酯和胺类化合物对映体的分析。 相似文献
19.
Yung K. Kim George A. Grindahl John R. Greenwald Ogden R. Pierce 《Journal of heterocyclic chemistry》1974,11(4):563-568
The synthesis of 2-oxa and 2-thiaperfluoroglutaric acids and their corresponding ethyl esters, amides, nitriles, acid chlorides, and also 2-thiaperfluoroglutaric anhydride are described. These compounds were prepared as precursors to α,ω-ditriazinylperfluoroalkane derivatives containing a heteroatom in the perfluoroalkylene chain. The ditrazinylpropanes were prepared most satisfactorily from the diacid chlorides rather than the dinitriles. 相似文献
20.
Antonio J. LaPorte Jack E. Feldner Jan C. Spies Tom J. Maher Prof. Martin D. Burke 《Angewandte Chemie (International ed. in English)》2023,62(40):e202309566
Multifunctional organoboron compounds increasingly enable the simple generation of complex, Csp3-rich small molecules. The ability of boron-containing functional groups to modify the reactivity of α-radicals has also enabled a myriad of chemical reactions. Boronic esters with vacant p-orbitals have a significant stabilizing effect on α-radicals due to delocalization of spin density into the empty orbital. The effect of coordinatively saturated derivatives, such as N-methyliminodiacetic acid (MIDA) boronates and counterparts, remains less clear. Herein, we demonstrate that coordinatively saturated MIDA and TIDA boronates stabilize secondary alkyl α-radicals via σB-N hyperconjugation in a manner that allows site-selective C−H bromination. DFT calculated radical stabilization energies and spin density maps as well as LED NMR kinetic analysis of photochemical bromination rates of different boronic esters further these findings. This work clarifies that the α-radical stabilizing effect of boronic esters does not only proceed via delocalization of radical character into vacant boron p-orbitals, but that hyperconjugation of tetrahedral boron-containing functional groups and their ligand electron delocalizing ability also play a critical role. These findings establish boron ligands as a useful dial for tuning reactivity at the α-carbon. 相似文献