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1.
Steven Bloom Desta Doro Bume Cody Ross Pitts Prof. Dr. Thomas Lectka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8060-8063
To expand upon the recent pioneering reports of catalyzed sp3 C?H fluorination methods, the next rational step is to focus on directing “radical‐based fluorination” more effectively. One potential solution entails selective C?C bond activation as a prelude to selective fluorination. Herein, we report the tandem photocatalyzed ring‐opening/fluorination reactions of cyclopropanols by 1,2,4,5‐tetracyanobenzene (TCB) and Selectfluor to afford a process tantamount to site‐selective β‐fluorination of carbonyl‐containing compounds. This new approach provides a synthetically mild and operationally simple route to otherwise difficult‐to‐prepare β‐fluorinated products in good yields and with good‐to‐excellent regioselectivity. Remarkably, substrates that contain other usually reactive (e.g., benzylic) sites undergo ring‐opening fluorination preferably. The versatility of this method to give cyclic β‐fluorides from tertiary cyclopropanols and γ‐fluoro alcohols is also highlighted. 相似文献
2.
Dr. Yuwen Zeng Dr. Guangyu Li Prof. Dr. Jinbo Hu 《Angewandte Chemie (International ed. in English)》2015,54(37):10773-10777
Described is a one‐pot vicinal fluorination‐iodination of arynes at room temperature. The diphenyliodonium salt proved to be a privileged catalyst for this nucleophilic fluorination process using CsF as a fluorine source, and a subsequent facile electrophilic iodination with C4F9I was also found to be crucial to ensure the efficient fluorination. This new synthetic protocol has a broad substrate scope under mild reaction conditions. 相似文献
3.
A Convenient Late‐Stage Fluorination of Pyridylic C−H Bonds with N‐Fluorobenzenesulfonimide
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Michael Meanwell Dr. Matthew B. Nodwell Dr. Rainer E. Martin Prof. Robert Britton 《Angewandte Chemie (International ed. in English)》2016,55(42):13244-13248
Pyridine features prominently in pharmaceuticals and drug leads, and methods to selectively manipulate pyridine basicity or metabolic stability are highly sought after. A robust, metal‐free direct fluorination of unactivated pyridylic C?H bonds was developed. This convenient reaction shows high functional‐group tolerance and offers complimentary selectivity to existing C?H fluorination strategies. Importantly, this late‐stage pyridylic C?H fluorination provides opportunities to rationally modulate the basicity, lipophilicity, and metabolic stability of alkylpyridine drugs. 相似文献
4.
Kazuaki Ishihara Kazuki Nishimura Katsuya Yamakawa 《Angewandte Chemie (International ed. in English)》2020,59(40):17641-17647
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
5.
Alexander P. Kharitonov Galina V. Simbirtseva Vyacheslav M. Bouznik Maxim G. Chepezubov Marc Dubois Katia Guérin Andre Hamwi Hayat Kharbache Francis Masin 《Journal of polymer science. Part A, Polymer chemistry》2011,49(16):3559-3573
Chemical–physical properties of ultra‐high‐molecular weight polyethylene (UHMWPE) treated by direct fluorination, direct fluorination accompanied with UV irradiation, by XeF2 and by TbF4, were tested by FTIR spectroscopy, visible spectroscopy, 19F and 13C NMR, scanning electron microscopy, XRD, and EPR. Surface energy measurements were carried out. The direct fluorination of UHMWPE is a diffusion‐controlled process, but treatment with XeF2 is a kinetically controlled one. Direct fluorination and direct fluorination accompanied with UV irradiation results mainly in a formation of ? CF2? groups. On the contrary, ? CHF? groups are prevailing in UHMWPE treated with XeF2 and TbF4. Surface texture of UHMWPE treated with XeF2 and with F2 is quite different. Direct fluorination results in a higher polarity of the polymer surface when compared with treatment with XeF2. For the case of direct fluorination, both long‐lived peroxy and fluoroalkylradicals are formed. For the case of treatment with XeF2, only fluoroalkylradicals were detected. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49:3559–3573, 2011 相似文献
6.
Hiromichi Egami Taiki Rouno Tomoki Niwa Kousuke Masuda Kenji Yamashita Yoshitaka Hamashima 《Angewandte Chemie (International ed. in English)》2020,59(33):14101-14105
A linked dicarboxylate phase‐transfer catalyst enables smooth asymmetric dearomative fluorination of 2‐naphthols with Selectfluor under mild conditions to give the corresponding 1‐fluoronaphthalenone derivatives in a highly enantioselective manner. This reaction, which is compatible with a range of functional groups, is the first example of catalytic asymmetric fluorination of 2‐naphthols, and is expected to be useful in the synthesis of bioactive molecules. 相似文献
7.
Dr. Guo‐Qiang Xu Hui Liang Jie Fang Dr. Zhi‐Long Jia Dr. Jian‐Qiang Chen Prof. Dr. Peng‐Fei Xu 《化学:亚洲杂志》2016,11(23):3355-3358
The first highly enantioselective α‐fluorination of 2‐acyl imidazoles utilizing iridium catalysis has been accomplished. This transformation features mild conditions and a remarkably broad substrate scope, providing an efficient and highly enantioselective approach to obtain a wide range of fluorine‐containing 2‐acyl imidazoles which are found in a variety of bioactive compounds and prodrugs. A large scale synthesis has also been tested to demonstrate the potential utility of this fluorination method. 相似文献
8.
Rhodium‐Catalyzed Geminal Oxyfluorination and Oxytrifluoro‐Methylation of Diazocarbonyl Compounds
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Dr. Weiming Yuan Dr. Lars Eriksson Prof. Kálmán J. Szabó 《Angewandte Chemie (International ed. in English)》2016,55(29):8410-8415
A new reaction for the rhodium‐catalyzed geminal‐difunctionalization‐based fluorination is presented. The substrates are aromatic and aliphatic diazocarbonyl compounds. As the fluorine source a stable and easily accessible benziodoxole reagent was used. A variety of alcohol, phenol, and carboxylic acid reagents were employed to introduce the second functionality. The reaction was extended to trifluoromethylation using a benziodoxolon reagent. The fluorination and trifluoromethylation reactions probably proceed by a rhodium‐containing onium ylide type intermediate, which is trapped by either the F or CF3 electrophiles. 相似文献
9.
The treatment of a β3‐amino acid methyl ester with 2.2 equiv. of lithium diisopropylamide (LDA), followed by reaction with 5 equiv. of N‐fluorobenzenesulfonimide (NFSI) at ?78° for 2.5 h and then 2 h at 0°, gives syn‐fluorination with high diastereoisomeric excess (de). The de and yield in these reactions are somewhat influenced by both the size of the amino acid side chain and the nature of the amine protecting group. In particular, fluorination of N‐Boc‐protected β3‐homophenylalanine, β3‐homoleucine, β3‐homovaline, and β3‐homoalanine methyl esters, 5 and 9 – 11 , respectively, all proceeded with high de (>86% of the syn‐isomer). However, fluorination of N‐Boc‐protected β3‐homophenylglycine methyl ester ( 16 ) occurred with a significantly reduced de. The use of a Cbz or Bz amine‐protecting group (see 3 and 15 ) did not improve the de of fluorination. However, an N‐Ac protecting group (see 17 ) gave a reduced de of 26%. Thus, a large N‐protecting group should be employed in order to maximize selectivity for the syn‐isomer in these fluorination reactions. 相似文献
10.
Xiuqin Dong Wen Yang Weimin Hu Jianwei Sun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(2):670-673
The asymmetric fluorination of azolium enolates that are generated from readily available simple aliphatic aldehydes or α‐chloro aldehydes and N‐heterocyclic carbenes (NHCs) is described. The process significantly expands the synthetic utility of NHC‐catalyzed fluorination and provides facile access to a wide range of α‐fluoro esters, amides, and thioesters with excellent enantioselectivity. Pyrazole was identified as an excellent acyl transfer reagent for catalytic amide formation. 相似文献
11.
《中国化学会会志》2017,64(10):1128-1138
High‐surface‐area chromium‐based catalysts in the presence of a small amount of zinc were prepared via a sol–gel auto‐combustion method using chromic nitrate, zinc nitrate, and citric acid. First, the auto‐combustion behavior of the dried gel was investigated by derivative thermogravimetry and (DTG)‐TG and infrared (IR) techniques. The results revealed that the dried gel exhibited self‐propagating combustion properties. Second, the as‐burnt powders were characterized by IR , X‐ray diffraction (XRD) , Brunauer–Emmett–Teller analysis (BET) , and scanning electron microscopy (SEM) . The findings showed that the gels were directly converted into CrZn ‐O nanoparticles with high surface area during the auto‐combustion process. Third, the pre‐fluorination Cr‐Zn catalysts were characterized by XRD , BET , SEM , X‐ray photoelectron spectroscopy (XPS) , and Fourier transform (FT)‐IR spectroscopy of pyridine adsorption techniques. It was found that the presence of zinc led to significant structural changes in the catalyst, the particle size was smaller, the surface area became larger, and more active sites appeared. Finally, the catalytic activities of the samples were tested for the fluorination of 1,2‐dichlorohexafluorocyclopentene (1,2‐F6 ) with anhydrous hydrogen fluoride. The obtained results indicated that the pre‐fluorination activated Cr‐Zn catalysts prepared by this sol–gel auto‐combustion method exhibited high efficiency in the synthesis of cyclic hydrofluorocarbons. 相似文献
12.
Bis‐tert‐Alcohol‐Functionalized Crown‐6‐Calix[4]arene: An Organic Promoter for Nucleophilic Fluorination
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Dr. Vinod H. Jadhav Wonsil Choi Sung‐Sik Lee Prof. Dr. Sungyul Lee Prof. Dr. Dong Wook Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4515-4520
A bis‐tert‐alcohol‐functionalized crown‐6‐calix[4]arene (BACCA) was designed and prepared as a multifunctional organic promoter for nucleophilic fluorinations with CsF. By formation of a CsF/BACCA complex, BACCA could release a significantly active and selective fluoride source for SN2 fluorination reactions. The origin of the promoting effects of BACCA was studied by quantum chemical methods. The role of BACCA was revealed to be separation of the metal fluoride to a large distance (>8 Å), thereby producing an essentially “free” F?. The synergistic actions of the crown‐6‐calix[4]arene subunit (whose O atoms coordinate the counter‐cation Cs+) and the terminal tert‐alcohol OH groups (forming controlled hydrogen bonds with F?) of BACCA led to tremendous efficiency in SN2 fluorination of base‐sensitive substrates. 相似文献
13.
N‐Heterocyclic Carbene Catalyzed Enantioselective α‐Fluorination of Aliphatic Aldehydes and α‐Chloro Aldehydes: Synthesis of α‐Fluoro Esters,Amides, and Thioesters
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Dr. Xiuqin Dong Dr. Wen Yang Dr. Weimin Hu Prof. Dr. Jianwei Sun 《Angewandte Chemie (International ed. in English)》2015,54(2):660-663
The asymmetric fluorination of azolium enolates that are generated from readily available simple aliphatic aldehydes or α‐chloro aldehydes and N‐heterocyclic carbenes (NHCs) is described. The process significantly expands the synthetic utility of NHC‐catalyzed fluorination and provides facile access to a wide range of α‐fluoro esters, amides, and thioesters with excellent enantioselectivity. Pyrazole was identified as an excellent acyl transfer reagent for catalytic amide formation. 相似文献
14.
A Facile Top‐Down Protocol for Postsynthesis Modification of Hierarchical Aluminum‐Rich MFI Zeolites
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Lili Yu Dr. Shengjun Huang Dr. Shu Miao Fucun Chen Shuang Zhang Zhenni Liu Prof. Sujuan Xie Prof. Dr. Longya Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1048-1054
High aluminum content constitutes a major hurdle for the postsynthesis modification of hierarchical zeolites. A facile protocol comprising fluorination and sequential alkaline treatment is presented for the postsynthesis modification of hierarchical Al‐rich MFI zeolites. By virtue of this protocol, uniform intracrystalline mesoporosity is introduced in an Al‐rich MFI zeolite (Si/Al=14.3). The obtained hierarchical zeolites exhibit a significant mesopore size distribution, centered around 6 nm, and show improved conversions in catalytic cracking of bulky aromatic molecules. The fundamental implications of the fluorination–alkaline treatment protocol are related to the formation of F‐bearing tetrahedral aluminum species in the antecedent fluorination step, which alleviates the resistance of Al sites to the alkaline medium and causes Al?F complexation for regulated hydrolysis of the Al species during the alkaline treatment process. This top‐down protocol and the derived mechanistic understandings are expected to be applied in the synthesis of hierarchical Al‐rich zeolites with other framework topologies. 相似文献
15.
Palladium‐Catalyzed Fluorination of Cyclic Vinyl Triflates: Effect of TESCF3 as an Additive
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Yuxuan Ye Prof. Dr. Takashi Takada Prof. Dr. Stephen L. Buchwald 《Angewandte Chemie (International ed. in English)》2016,55(50):15559-15563
A method for the palladium‐catalyzed fluorination of cyclic vinyl triflates has been developed. As with several previous palladium‐catalyzed fluorination reactions using fluoride salts, controlling the regioselectivity presented a challenge in developing a practical synthetic procedure. The addition of triethyl(trifluoromethyl)silane (TESCF3) was found to effectively address this problem and resulted in drastically improved regioselectivities in this palladium‐catalyzed fluorination reaction. This discovery, along with the use of a new biarylphosphine ligand, allowed for the development of an efficient and highly regioselective protocol for the fluorination of vinyl triflates. This method is compatible with a range of sensitive functional groups and provides access to five‐, six‐, and seven‐membered cyclic vinyl fluorides. 相似文献
16.
Dr. Theresa Liang Constanze N. Neumann Prof. Tobias Ritter 《Angewandte Chemie (International ed. in English)》2013,52(32):8214-8264
Over the past decade, the most significant, conceptual advances in the field of fluorination were enabled most prominently by organo‐ and transition‐metal catalysis. The most challenging transformation remains the formation of the parent C? F bond, primarily as a consequence of the high hydration energy of fluoride, strong metal—fluorine bonds, and highly polarized bonds to fluorine. Most fluorination reactions still lack generality, predictability, and cost‐efficiency. Despite all current limitations, modern fluorination methods have made fluorinated molecules more readily available than ever before and have begun to have an impact on research areas that do not require large amounts of material, such as drug discovery and positron emission tomography. This Review gives a brief summary of conventional fluorination reactions, including those reactions that introduce fluorinated functional groups, and focuses on modern developments in the field. 相似文献
17.
Leming Wang Xinhang Jiang Jiean Chen Yong Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7488-7492
In contrast to well‐established asymmetric hydrogenation reactions, enantioselective protonation is an orthogonal approach for creating highly valuable methine chiral centers under redox‐neutral conditions. Reported here is the highly enantio‐ and diastereoselective hydrofluorination of enals by an asymmetric β‐protonation/α‐fluorination cascade catalyzed by N‐heterocyclic carbenes (NHCs). The two nucleophilic sites of a homoenolate intermediate, generated from enals and an NHC, are sequentially protonated and fluorinated. The results show that controlling the relative rates of protonation, fluorination, and esterification is crucial for this transformation, and can be accomplished using a dual shuttling strategy. Structurally diverse carboxylic acid derivatives with two contiguous chiral centers are prepared in a single step with excellent d.r. and ee values. 相似文献
18.
A facile and direct fluorination process of alkynes and diynes was developed. In the presence of n‐butyllithium, the reaction of a series of terminal alkynes and diynes with the electrophilic fluorinating reagent (NFSI) proceeded to afford various 1‐fluoroalkynes and 1‐fluoro‐1,3‐diynes in moderate to high yields. 相似文献
19.
α‐Fluoro‐o‐cresols: The Key Role of Intramolecular Hydrogen Bonding in Conformational Preference and Hydrogen‐Bond Acidity
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Dr. Elena Bogdan Alexis Quarré de Verneuil François Besseau Dr. Guillaume Compain Prof. Dr. Bruno Linclau Prof. Dr. Jean‐Yves Le Questel Dr. Jérôme Graton 《Chemphyschem》2016,17(17):2702-2709
20.
Aleksei B. Sheremetev Natali S. Aleksandrova Svyatoslav S. Semyakin Kyrill Yu. Suponitsky David B. Lempert 《化学:亚洲杂志》2019,14(23):4255-4261
The synthesis of a new energetic 1,2,4‐triazole compound bearing nitrofurazanyl and fluorodinitromethyl units, which may find use as a component for rocket ramjet engines (RRE), is described. The target product was prepared in a four‐step process applying oxidation/nitration/decarboxylation/fluorination reactions and is fully characterized. Its density and structural features were uniquely determined by X‐ray analysis. It is shown that replacing HMX with the compound of this study in boron‐based fuels gives an increase in energy. 相似文献