共查询到20条相似文献,搜索用时 15 毫秒
1.
The rhodium–NHC catalyzed arylation reaction of ethyl glyoxalate with aryl and alkyl boronic acids provides an efficient method for the synthesis of α-hydroxyesters. A wide range of α-hydroxyesters (up to 12) were prepared in good to excellent yields. KOtBu was the base of choice, along with tert-amyl alcohol as the solvent. As far as we are aware, this is the first report of this catalytic arylation, using rhodium–NHC catalysts with this specific substrate type. 相似文献
2.
Tasimelteon is a useful drug for the treatment of Non-24 in totally blind individuals. An efficient and convenient asymmetric synthesis of tasimelteon has been developed from 4-vinyl-2,3-dihydrobenzofuran through six steps in 53% overall yield using the Corey–Bakshi–Shibata (CBS0 asymmetric reduction of ketone as a key step. 相似文献
3.
Ekaterina V. Matveeva Pavel V. Petrovskii Zinaida S. Klemenkova Natalya A. Bondarenko Irina L. Odinets 《Comptes Rendus Chimie》2010,13(8-9):964-970
Biphasic systems room temperature imidazolium ionic liquid (RTIL)/water or water as a solvent significantly accelerate the addition of amines to vinylphosphoryl compounds hence opening green and effective synthesis of β-aminophosphoryl compounds in excellent yields over short reaction times. The application of water, being the cheapest and most non-toxic solvent, without any catalyst or co-solvent, is more advantageous as it provides a simple isolation procedure for products having high purity (> 95% according to the NMR data) via simple freeze-drying and does not require extraction with organic solvents. The solubility of the starting phosphorus substrate in water does not play crucial role in the reaction as it was demonstrated using water insoluble diphenylvinylphosphine oxide. In contrast to typical procedures, using a reactant ratio (vinylphosphoryl compound: amine) of 2:1 readily resulted in double phosphorylation of primary amines, including polyamines, in water. 相似文献
4.
A practical synthesis of novel α-dibromoalkyl- and trimethylsilylmethyl-aminoboranes and derivatives
Söyleyici HC Fırıncı E Eyduran F Akbulat F Sahin Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(3):1139-1142
Addition of LDA to a mixture of trimethylborate and dibromomethane in THF at a temperature of -78°C leads to the formation of dibromomethyllithium and its capture by borate ester. ClB(OMe)(2) converts the resulting borate salt to dimethoxy(dibromomethyl)borane 2. N,N-Dimethylamino(methoxy)(dibromomethyl)borane 3 and N,N-bis(dimethylamino)(dibromomethyl)borane 4 were prepared by an amination reaction between N,N-dimethylaminotrimethylsilane and dimethoxy(dibromomethyl)borane 2. To obtain dichlorotrimethylsilylmethylborane 7 not containing the α-halomethyl group, N,N-bis(dimethylamino)(trimethylsilylmethyl)borane 5 was first obtained from the reaction of ClB(NMe(2))(2) with an organolithium reagent. Dimethoxy(trimethylsilylmethyl)borane 6 was then prepared by methoxylation of compound 5. Finally, compound 7 was prepared by chlorination of 6 using BCl(3). The chemical structures of these compounds were determined using (13)C, (1)H, (11)B NMR and GC/MS/MS techniques. 相似文献
5.
Trost BM Taft BR Masters JT Lumb JP 《Journal of the American Chemical Society》2011,133(22):8502-8505
A new strategy for the synthesis of chiral β-alkynyl esters which relies on sequential Pd and Cu catalysis is reported. Terminal alkynes bearing aryl, alkyl, and silyl groups can be employed without prior activation yielding a wide range of important chiral building blocks. The reaction sequence utilizes a robust Pd(II)-catalyzed hydroalkynylation of ynoates with terminal alkynes providing geometrically pure ynenoates which are readily reduced by CuH. In contrast to previous reports, where additions to ynenoates proceed with marginal preference for the 1,6-pathway, this conjugate reduction occurs with high 1,4-selectivity yielding β-alkynyl esters with excellent levels of enantioselectivity. Importantly, the method tolerates a wide range of functionality, including allylic carbonates and carbamates, and thus allows for rapid elaboration of the β-alkynyl esters into a variety of chiral, substituted heterocycles. 相似文献
6.
《Mendeleev Communications》2021,31(5):620-623
The chemical oxidation of rhodium(i) complexes [Rh(L)(COD)][BF4], where L is a ferrocenyl phosphine/N-heterocyclic carbene ligand, with 2 equiv. of a triaryl-aminium salt [(4-BrC6H4)3N][BF4] in acetonitrile gave planar chiral, air-stable [Rh(L–H)(MeCN)3][BF4]2 complexes where the ferrocene (C5H4CH2ImR or C5H4CH2BImCH2Mes) ring has been C–H activated at the position 2 in good to excellent yields. An important reactivity difference between our complexes and the ubiquitous [Cp*Rh(MeCN)3]X2 complex has been observed in the Grignard-type arylation of 4-nitrobenzaldehyde. 相似文献
7.
Ascic E Hansen CL Le Quement ST Nielsen TE 《Chemical communications (Cambridge, England)》2012,48(27):3345-3347
An efficient and broadly applicable alternative to the classical Pictet-Spengler synthesis of tetrahydro-β-carbolines is presented. The method relies on metal-catalyzed isomerization of allylic amines to form reactive iminium intermediates which can be trapped by a tethered indole nucleophile. 相似文献
8.
An efficient rhodium/diene-catalyzed asymmetric addition of arylboronic acids to α,β-unsaturated γ-lactams has been developed. The power of this methodology is further demonstrated by the concise synthesis of (R)-baclofen and (R)-rolipram. 相似文献
9.
SbCl3 adsorbed on Al2O3 is found to be an efficient and recyclable catalyst in promoting three-component coupling reactions of aldehydes (aromatic and aliphatic), amines (aryl amines, aliphatic amines and esters of S-α-amino acids) and dialkylphosphites to afford the corresponding α-aminophosphonates in high yields. The ethyl ester of S-phenylalanine was observed to yield the corresponding α-aminophosphonate with S,S-diastereoisomer formed in dominance over the S,R-diastereoisomer. 相似文献
10.
正Producing biofuels from renewable biomass resources is considered to be an effective way to reduce carbon emissions and is helpful for establishing sustainable society [1]. Bio‐methane (CH4) is a promising and available clean energy in the future owing to its properties such as high calorific values, low carbon emissions and full miscibility and interchangeability with natural gas or shale gas. Therefore, the production of me‐thane directly from waste biomass resources like straw is highly attractive. However, because of the robustness and vari‐ety of C–C bonds and C–O bonds existing in biomass molecules,it is very difficult to achieve high‐selective methanation of bio‐ 相似文献
11.
Treatment of N-phenyl-iododifluoroacetamide (1) with terminal alkenes (2) in the presence of Na2S2O4 and NaHCO3 in CH3CN/H2O gave good yields of N-phenyl-2,2-difluoro-4-iodoalkanamide (3), which cyclized under strong basic conditions to afford N-phenyl-α,α-difluoro-γ-lactams (4). Or simply, these lactams 4 can be directly prepared in one-pot from 1 and 2 in the presence of Na2S2O4 and NaOH. 相似文献
12.
《Mendeleev Communications》2021,31(5):677-679
Novel approach to methyl 2-aryl-2-(arylhydrazono) acetates via methanolysis of dichlorodiazabutadienes was developed. Hydrogen bonding in methyl Z-2-phenyl-2-(phenyl-hydrazono) acetate was explored by DFT calculations and topological analysis of the electron density distribution within the framework of Bader’s theory (QTAIM method). 相似文献
13.
Rui Umeda Yuji Shimizu Yuta Ida Masahiro Ikeshita Shuichi Suzuki Takeshi Naota Yutaka Nishiyama 《Tetrahedron letters》2019,60(2):183-186
π-Extended oxepins 1 and dimer 8 were synthesized by the benzannulation of the corresponding asymmetric diarylacetylene derivatives and 2-(phenylethynyl)benzaldehyde followed by the Cu-catalyzed intramolecular cyclization. The optical properties of the π-extended oxepins 1 and 8 are also investigated. 相似文献
14.
Xiang-zheng Tang Jing-xuan zhou Hua-ju Liang Xue-jing Zhang Ming Yan Albert S.C. Chan 《Tetrahedron letters》2019,60(2):147-149
A straightforward synthesis of isoindolinones has been developed via a [3?+?3] benzannulation of 4-arylmethylene-2,3-dioxopyrrolidines and 1,3-bissulfonylpropenes (or 4-sulfonylcrotonates). A series of functionalized isoindolinones were obtained in excellent yields. The reaction could be carried out under mild conditions without transition metal catalyst. The finding provides a practical approach for the preparation of isoindolinone derivatives with potential biological activities. 相似文献
15.
The enantioselective α-vinylation of aldehydes using vinyl iodonium triflate salts has been accomplished via the synergistic combination of copper and chiral amine catalysis. These mild catalytic conditions provide a direct route for the enantioselective construction of enolizable α-formyl vinylic stereocenters without racemization or olefin transposition. These high-value coupling adducts are readily converted into a variety of useful olefin synthons. 相似文献
16.
《中国化学快报》2023,34(3):107647
Catalytic asymmetric dearomatization of indoles and alkynes has received much attention in the past decade because this strategy offers an attractive and alternative way for the efficient synthesis of valuable chiral polycyclic indolines. However, these reactions have been mostly limited to transition-metal catalysts, and the related chiral Brønsted acid catalysis has been scarcely reported. Herein, we disclose a chiral phosphoric acid-catalyzed asymmetric dearomatization of indolyl ynamides by direct activation of alkynes. This metal-free method enables the practical and atom-economical construction of an array of valuable chiral polycyclic indolines in moderate to good yields with high enantioselectivities 相似文献
17.
An efficient enantioselective approach to form trans-γ-lactams in up to 99% yield, 93% ee, and >20/1 dr using unactivated imines has been developed. The cyclohexyl-substituted azolium and the weak base sodium o-chlorobenzoate are most suitable for this transformation. Notably, the process involves cooperative catalysis by an N-heterocyclic carbene and a Br?nsted acid. 相似文献
18.
In recent years, considerable efforts have been expended to the development ofenantioselective synthesis of α-amino acids and the use of α-amino acids as chiralbuilding blocks for the synthesis of complex molecules. Numerous unnatural aminoacids which are often the characteristic units of biologically active peptides, have alsobeen discovered. Herein we describe a convenient and general access to natural andunnatural α-amino acids which are based on the use of the chiral building blocks,(S)-1a-e and (R)-1a-e from kinetic resolution of α-furfuryl amines (Scheme 1). 相似文献
19.
Pol Karier Gheorghe C. Catrinescu Nicolas Diercxsens Koen Robeyns Michael L. Singleton István E. Markó 《Tetrahedron》2018,74(51):7242-7251
A modulable tin based allylation method for the synthesis of 1,2,3-triols is described. The optimization of the reaction was aided by 1H and 119Sn low temperature NMR spectroscopic investigations, which support the formation of two cyclic intermediates after transmetallation. Depending on the nature of the Lewis acid, either syn/anti or anti/syn configured triols could be obtained with good stereocontrol. To demonstrate the value of this methodology and the resulting scaffolds, they were used to install the signature triol motifs of (?)-cleistenolide and of herbarumin I. 相似文献
20.
Enantiomerically enriched cyclopropanes and products of C–H insertion reactions were obtained in excellent combined yields and enantioselectivities as a consequence of rhodium-catalyzed decomposition of vinyl diazoacetate in the presence of tert-butoxycarbonyl-(Boc)-protected amines as trapping agents. A series of enantiomerically enriched six- to eight-membered nitrogen-containing heterocycles were subsequently prepared via ring-closing metathesis of the dienes catalyzed by ruthenium benzylidene complex. 相似文献