共查询到20条相似文献,搜索用时 15 毫秒
1.
Hongchao Zheng Robert McDonald Dr. Dennis G. Hall Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(18):5454-5460
Herein, the concept of boronic acid catalysis (BAC) for the activation of unsaturated carboxylic acids is applied in several classic dipolar [3+2] cycloadditions involving azides, nitrile oxides, and nitrones as partners. These cycloadditions can be used to produce pharmaceutically interesting, small heterocyclic products, such as triazoles, isoxazoles, and isoxazolidines. These cycloadducts are formed directly and include a free carboxylic acid functionality that can be employed for further transformations, thereby avoiding prior masking or functionalization. In all cases, BAC provides faster reactions, under milder conditions, with much improved product yields and regioselectivities. In some instances, such as triazole formation from the reaction of azides with 2‐alkynoic acids, catalysis with ortho‐nitrophenylboronic acid circumvents the undesirable product decarboxylation observed when using thermal activation. By using NMR spectroscopic studies, the boronic acid catalyst was shown to provide activation by a LUMO‐lowering effect in the unsaturated carboxylic acid, likely via a monoacylated hemiboronic ester intermediate. 相似文献
2.
Takahiro Horibe Takashi Hazeyama Yuto Nakata Kazuki Takeda Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2020,59(39):17256-17260
An enantioselective 1,4‐addition of α,β‐unsaturated carboxylic acids with cycloalkanones has been developed by using chiral amine–boronic acid cooperative catalysts. In the presence of a chiral amine and boronic acid, cycloalkanones and carboxylic acids are activated as chiral enamines and mixed anhydrides, respectively. The corresponding 1,4‐adducts are obtained in high yield with high enantioselectivity. Furthermore, subsequent oxylactonization of the 1,4‐adducts gives spirolactones with high diastereoselectivity. 相似文献
3.
Dr. Takahiro Horibe Takashi Hazeyama Yuto Nakata Kazuki Takeda Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17409-17413
An enantioselective 1,4-addition of α,β-unsaturated carboxylic acids with cycloalkanones has been developed by using chiral amine–boronic acid cooperative catalysts. In the presence of a chiral amine and boronic acid, cycloalkanones and carboxylic acids are activated as chiral enamines and mixed anhydrides, respectively. The corresponding 1,4-adducts are obtained in high yield with high enantioselectivity. Furthermore, subsequent oxylactonization of the 1,4-adducts gives spirolactones with high diastereoselectivity. 相似文献
4.
Br?nsted base-assisted boronic acid catalysis for the dehydrative self-condensation of carboxylic acids is described. Arylboronic acid bearing bulky (N,N-dialkylamino)methyl groups at the 2,6-positions can catalyze the intramolecular dehydrative condensation of di- and tetracarboxylic acids. This is the first successful method for the catalytic dehydrative self-condensation of carboxylic acids. 相似文献
5.
Decarboxylative Conjunctive Cross-coupling of Vinyl Boronic Esters using Metallaphotoredox Catalysis
Riccardo S. Mega Vincent K. Duong Dr. Adam Noble Prof. Dr. Varinder K. Aggarwal 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(11):4405-4409
The synthesis of complex alkyl boronic esters through conjunctive cross-coupling of vinyl boronic esters with carboxylic acids and aryl iodides is described. The reaction proceeds under mild metallaphotoredox conditions and involves an unprecedented decarboxylative radical addition/cross-coupling cascade of vinyl boronic esters. Excellent functional-group tolerance is displayed, and application of a range of carboxylic acids, including secondary α-amino acids, and aryl iodides provides efficient access to highly functionalized alkyl boronic esters. The decarboxylative conjunctive cross-coupling was also applied to the synthesis of sedum alkaloids. 相似文献
6.
New mono boronic acid was found to be an enantioselective fluorescent chemosensor for mono alpha-hydroxyl carboxylic acids, such as mandelic acid and lactic acid. The chiral sensor shows lower background fluorescence, higher fluorescence enhancement, and enantioselective recognition kinetics toward mandelic acids and lactic acids. 相似文献
7.
O-Methyl hydroxamic acids, readily available from carboxylic acids, are found to be extremely reactive for beta-C-H activation by Pd(OAc)2. This reactivity is exploited to develop the first example of cross-coupling sp3 C-H bonds with sp3 boronic acids. Air was shown to be a suitable stoichiometric oxidant for the catalytic oxidative coupling reaction. A biologically active natural product is readily converted to its novel analogues through this coupling reaction. 相似文献
8.
Decarboxylative Conjunctive Cross‐coupling of Vinyl Boronic Esters using Metallaphotoredox Catalysis
Riccardo S. Mega Vincent K. Duong Adam Noble Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2020,59(11):4375-4379
The synthesis of complex alkyl boronic esters through conjunctive cross‐coupling of vinyl boronic esters with carboxylic acids and aryl iodides is described. The reaction proceeds under mild metallaphotoredox conditions and involves an unprecedented decarboxylative radical addition/cross‐coupling cascade of vinyl boronic esters. Excellent functional‐group tolerance is displayed, and application of a range of carboxylic acids, including secondary α‐amino acids, and aryl iodides provides efficient access to highly functionalized alkyl boronic esters. The decarboxylative conjunctive cross‐coupling was also applied to the synthesis of sedum alkaloids. 相似文献
9.
Synthesis of Aldehydes by Organocatalytic Formylation Reactions of Boronic Acids with Glyoxylic Acid
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(28):8313-8317
Reported herein is a conceptually novel organocatalytic strategy for the formylation of boronic acids. New reactivity is engineered into the α‐amino‐acid‐forming Petasis reaction occurring between aryl boronic acids, amines, and glyoxylic acids to prepare aldehydes. The operational simplicity of the process and its ability to generate structurally diverse and valued aryl, heteroaryl, and α,β‐unsaturated aldehydes containing a wide array of functional groups, demonstrates the practical utility of the new synthetic strategy. 相似文献
10.
Hydrogen bonding is a key determinant of much macromolecular structure in nature, but individual donor and acceptor pairs are rarely observed in solution. Their weak interactions result in nanosecond lifetimes and rapid exchange of partners. Reversible encapsulation isolates molecules in very small spaces for milliseconds to hours and allows their characterization by NMR methods. Here we report a competitive study of hydrogen-bonding functions--carboxylic acids, primary amides, and boronic acids--within a multicomponent capsular assembly. The pairwise co-encapsulation of these molecules allows the direct observation of homodimeric boronic acids and their heterodimeric complexes with carboxylic acids and primary amides. The efficiency of boronic acids as hydrogen-bonding partners derives from their adaptable structures rather than from their intrinsic acid/base properties. 相似文献
11.
Dr. Jie Wang Dr. Tian Qin Dr. Tie‐Gen Chen Dr. Laurin Wimmer Jacob T. Edwards Dr. Josep Cornella Benjamin Vokits Dr. Scott A. Shaw Prof. Phil S. Baran 《Angewandte Chemie (International ed. in English)》2016,55(33):9676-9679
A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross‐coupling between alkyl‐carboxylic acids and boronic acids is described. This Ni‐catalyzed reaction relies upon the activation of alkyl carboxylic acids as their redox‐active ester derivatives, specifically N‐hydroxy‐tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl2?6 H2O—$9.5 mol?1, Et3N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption. 相似文献
12.
Yuko Mochizuki Shinsuke Inagaki Mayu Suzuki Jun Zhe Min Koichi Inoue Kenichiro Todoroki Toshimasa Toyo'oka 《Journal of separation science》2013,36(12):1883-1889
A novel bromoquinolinium reagent, i.e. 1‐(3‐aminopropyl)‐3‐bromoquinolinium bromide (APBQ), was synthesized for the analysis of carboxylic acids. A simple and practical precolumn derivatization procedure using the APBQ in RP chromatography and MS (HPLC‐MS) has been developed using bile acids and free fatty acids, as the representative carboxylic acids in biological samples. The APBQ efficiently reacted with carboxylic acids at 60°C for 60 min in the presence of N,N‐dicyclohexylcarbodiimide and pyridine as the activation reagents. Because the APBQ possesses a bromine atom in the structure, the identification of a series of carboxylic acids was easily achieved due to the characteristic bromine isotope pattern in the mass spectra. The APBQ also has a quaternary amine structure, thus the positively charged derivatives are predominate for the highly sensitive detection of carboxylic acids. The APBQ was successfully applied to the selective determination of biological carboxylic acids in human plasma. The bile acids (chenodeoxycholic acid and deoxycholic acid) and several saturated (stearic acid and palmitic acid) and unsaturated free fatty acids (oleic acid and linoleic acid) were reasonably determined by HPLC‐MS under the proposed procedure. Based on the results of analyses of human plasma and saliva, the proposed procedure using APBQ seems to be applicable for the qualitative and quantitative analyses of a series of carboxylic acids in biological samples. 相似文献
13.
Visible‐Light‐Mediated Decarboxylative Radical Additions to Vinyl Boronic Esters: Rapid Access to γ‐Amino Boronic Esters
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)
Dr. Adam Noble Riccardo S. Mega Dr. Daniel Pflästerer Dr. Eddie L. Myers Prof. Dr. Varinder K. Aggarwal 《Angewandte Chemie (International ed. in English)》2018,57(8):2155-2159
The synthesis of alkyl boronic esters by direct decarboxylative radical addition of carboxylic acids to vinyl boronic esters is described. The reaction proceeds under mild photoredox catalysis and involves an unprecedented single‐electron reduction of an α‐boryl radical intermediate to the corresponding anion. The reaction is amenable to a diverse range of substrates, including α‐amino, α‐oxy, and alkyl carboxylic acids, thus providing a novel method to rapidly access boron‐containing molecules of potential biological importance. 相似文献
14.
Riss PJ Lu S Telu S Aigbirhio FI Pike VW 《Angewandte Chemie (International ed. in English)》2012,51(11):2698-2702
Rapid and direct: the carboxylation of boronic acid esters with (11)CO(2) provides [(11)C]carboxylic acids as a convenient entry into [(11)C]esters and [(11)C]amides. This conversion of boronates is tolerant to diverse functional groups (e.g., halo, nitro, or carbonyl). 相似文献
15.
16.
1,3,5-tri-Oxygenated benzenes can serve as substrates for the Petasis boronic acid reaction, providing a practical synthetic route for the two CC bond formation of α-(1,3,5-tri-oxygenated phenyl)carboxylic acids. The scope and limitations of this method have been examined. 相似文献
17.
Kandasamy Jothivenkatachalam Singaravelu Chandra Mohan Paramasivan Natarajan 《Research on Chemical Intermediates》2013,39(7):3371-3386
Cobalt(III) ammine complexes coordinated to carboxylic acids are classic examples showing photoredox reactions originating from the ligand to metal charge transfer excited states. Cobalt(III) pentaammine complexes coordinated to unsaturated carboxylic acids as ligands were synthesized and characterized by spectroscopic methods. The photolysis of these complexes produces a carboxylate free radical. This free radical undergoes further transformation to form organic photoproducts. The organic photoproducts were characterized by spectroscopic methods. The nature of the decomposition products from the organic photoproduct was examined in detail. The quantum yields were also determined. The photochemical reactions have the potential to produce novel compounds from the decarboxylation of unsaturated acids, which shows interesting reaction pathways. 相似文献
18.
The reaction of lead tetraacetate with unsaturated carboxylic acids (or salts) to from bislactones (γ or δ) can be controlled to produce efficiently addition of two carboxylic oxygens to the double bond, in consonance with an initial plumbolactonization step followed by SN2 displacement of lead. 相似文献
19.
A Pd(II)/sulfoxide-catalyzed sequential allylic C-H oxidation/vinylic C-H arylation of alpha-olefins to furnish E-arylated allylic esters in high regio- and E:Z selectivities (>20:1) is reported. The broad scope of this method with respect to the alpha-olefin, carboxylic acid, and aryl boronic acid enables the rapid assembly of densely functionalized fragments for complex molecule synthesis from cheap, abundant hydrocarbon starting materials. The Pd(II)/sulfoxide-catalyzed vinylic C-H arylation of electronically unbiased olefins with aryl boronic acids proceeds under oxidative, acidic conditions and mild temperatures (room temperature to 45 degrees C). 相似文献