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1.
An efficient and modular entry to α‐halogenated amides and esters is reported. This reaction is based on an underestimated double electrophilic activation of ynamides sequentially involving highly reactive activated keteniminium and iminium ions. Upon simple reaction with HCl and an electrophilic halogenation reagent in the presence of water or an alcohol, a broad range of ynamides can be transformed, in a highly divergent manner, to α‐halo amides and esters with high efficiency and under mild conditions. 相似文献
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N. Chary Mamillapalli Prof. Govindasamy Sekar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18584-18588
Synthesis of enantiomerically enriched α‐hydroxy amides and β‐amino alcohols has been accomplished by enantioselective reduction of α‐keto amides with hydrosilanes. A series of α‐keto amides were reduced in the presence of chiral CuII/(S)‐DTBM‐SEGPHOS catalyst to give the corresponding optically active α‐hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one‐pot complete reduction of both ketone and amide groups of α‐keto amides has been achieved using the same chiral copper catalyst followed by tetra‐n‐butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β‐amino alcohol derivatives. 相似文献
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Chemoselective Reductive Nucleophilic Addition to Tertiary Amides,Secondary Amides,and N‐Methoxyamides 下载免费PDF全文
Minami Nakajima Yukiko Oda Takamasa Wada Ryo Minamikawa Dr. Kenji Shirokane Dr. Takaaki Sato Noritaka Chida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17565-17571
As the complexity of targeted molecules increases in modern organic synthesis, chemoselectivity is recognized as an important factor in the development of new methodologies. Chemoselective nucleophilic addition to amide carbonyl centers is a challenge because classical methods require harsh reaction conditions to overcome the poor electrophilicity of the amide carbonyl group. We have successfully developed a reductive nucleophilic addition of mild nucleophiles to tertiary amides, secondary amides, and N‐methoxyamides that uses the Schwartz reagent [Cp2ZrHCl]. The reaction took place in a highly chemoselective fashion in the presence of a variety of sensitive functional groups, such as methyl esters, which conventionally require protection prior to nucleophilic addition. The reaction will be applicable to the concise synthesis of complex natural alkaloids from readily available amide groups. 相似文献
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A general and efficient Cu(II)‐catalyzed cross‐coupling method is reported for the preparation of acyclic tertiary amides. Generally moderate to excellent yields and functional group tolerance were obtained with secondary acyclic amides and aryl halides as substrates in toluene. 相似文献
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Rachel C. Atkinson Dr. Fernando Fernández‐Nieto Josep Mas Roselló Prof. Jonathan Clayden 《Angewandte Chemie (International ed. in English)》2015,54(31):8961-8965
Available α‐amino acids undergo arylation at their α position in an enantioselective manner on treatment with base of N′‐aryl urea derivatives ligated to pseudoephedrine as a chiral auxiliary. In situ silylation and enolization induces diastereoselective migration of the N′‐aryl group to the α position of the amino acid, followed by ring closure to a hydantoin with concomitant explulsion of the recyclable auxiliary. The hydrolysis of the hydantoin products provides derivatives of quaternary amino acids. The arylation avoids the use of heavy‐metal additives, and is successful with a range of amino acids and with aryl rings of varying electronic character. 相似文献
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Christopher J. Teskey Pauline Adler Carlos R. Gonalves Nuno Maulide 《Angewandte Chemie (International ed. in English)》2019,58(2):447-451
We report a method for the selective α,β‐dehydrogenation of amides in the presence of other carbonyl moieties under mild conditions. Our strategy relies on electrophilic activation coupled to in situ selective selenium‐mediated dehydrogenation. The α,β‐unsaturated products were obtained in moderate to excellent yields, and their synthetic versatility was demonstrated by a range of transformations. Mechanistic experiments suggest formation of an electrophilic SeIV species. 相似文献
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Meijuan Yuan Yewen Fang Li Zhang Xiaoping Jin Minjia Tao Qilin Ye Ruifeng Li Jinjian Li Hui Zheng Juejun Gu 《中国化学》2015,33(10):1119-1123
The first palladium‐catalyzed method for the arylation of α‐phosphonovinyl nonaflates is described. Using a catalyst comprised of Pd(OAc)2 and SPhos, terminal and internal α‐aryl vinylphosphonates could be efficiently accessed under mild conditions. The reaction features a broad coupling partner scope and tolerates many functional groups. 相似文献
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Dr. Dmitry Katayev Prof. Yi‐Xia Jia Akhilesh K. Sharma Dr. Dipshikha Banerjee Dr. Céline Besnard Prof. Raghavan B. Sunoj Prof. E. Peter Kündig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):11916-11927
Palladium complexes incorporating chiral N‐heterocyclic carbene (NHC) ligands catalyze the asymmetric intramolecular α‐arylation of amides producing 3,3‐disubstituted oxindoles. Comprehensive DFT studies have been performed to gain insight into the mechanism of this transformation. Oxidative addition is shown to be rate‐determining and reductive elimination to be enantioselectivity‐determining. The synthesis of seven new NHC ligands is detailed and their performance is compared. One of them, L8 , containing a tBu and a 1‐naphthyl group at the stereogenic centre, proved superior and was very efficient in the asymmetric synthesis of fifteen new spiro‐oxindoles and three azaspiro‐oxindoles often in high yields (up to 99 %) and enantioselectivities (up to 97 % ee; ee=enantiomeric excess). Three palladacycle intermediates resulting from the oxidative addition of [Pd(NHC)] into the aryl halide bond were isolated and structurally characterized (X‐ray). Using these intermediates as catalysts showed alkene additives to play an important role in increasing turnover number and frequency. 相似文献
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Longji Li Yao Li Niankai Fu Long Zhang Sanzhong Luo 《Angewandte Chemie (International ed. in English)》2020,59(34):14347-14351
Asymmetric catalysis with benzyne remains elusive because of the highly fleeting and nonpolar nature of benzyne intermediates. Reported herein is an electrochemical approach for the oxidative generation of benzynes (cyclohexyne) and its successful merging with chiral primary aminocatalysis, formulating the first catalytic asymmetric enamine–benzyne (cyclohexyne) coupling reaction. Cobalt acetate was identified to stabilize the in situ generated arynes and facilitate its coupling with an enamine. This catalytic enamine‐benzyne protocol provides a concise method for the construction of diverse α‐aryl (α‐cyclohexenyl) quaternary carbon stereogenic centers with good stereoselectivities. 相似文献
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Johannes Schranck Mia Burhardt Christoph Bornschein Dr. Helfried Neumann Prof. Dr. Troels Skrydstrup Prof. Dr. Matthias Beller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9534-9538
A carbonylative α‐arylation process employing unactivated nitriles for the first time is described. The reaction tolerates a range of (hetero)aryl iodides and several nitrile coupling partners. No prefunctionalization of the nitriles is necessary and the resulting β‐ketonitriles are obtained in good to excellent yields. The methodology also allows for a convenient 13C‐labelling of the generated carbonyl moiety. 相似文献
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Yasushi Yoshida Kazuki Omori Tomohiko Hiroshige Takashi Mino Masami Sakamoto 《化学:亚洲杂志》2019,14(15):2737-2743
Chiral functionalized aminals are important core structures of natural products and pharmaceuticals. Their chemo‐ and regioselective catalytic, asymmetric synthesis has been realized through the umpolung reaction of α‐imino amides using a catalyst we originally developed. Functionalized aminals were prepared with high chemoselectivity by treating a hemiaminal intermediate with pyridine in butanol. Evaluation of substrate scope revealed that this transformation could be achieved with a wide range of α‐imino amides to produce the desired products in high yields with up to 97 % ee. A mechanistic study suggested that aminal formation proceeded through the ring opening/ring closing equilibrium of the hemiaminal skeleton. 相似文献
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Enrico Marelli Dr. Martin Corpet Sian R. Davies Prof. Dr. Steven P. Nolan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(52):17272-17276
A general catalytic protocol for the α‐arylation of aryl ketones has been developed. It involves the use of a preformed, bench‐stable Pd–N‐heterocyclic carbene pre‐catalyst bearing IHept as an ancillary ligand, and allows the coupling of various functionalized coupling partners at very low catalyst loading. Careful choice of the solvent/base system was crucial to obtain optimum catalyst performance. The pre‐catalyst was also successfully tested in the synthesis of an industrially relevant compound. 相似文献
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Anthony Millet David Dailler Dr. Paolo Larini Prof. Dr. Olivier Baudoin 《Angewandte Chemie (International ed. in English)》2014,53(10):2678-2682
The palladium‐catalyzed ligand‐controlled arylation of α‐zincated acyclic amines, obtained by directed α‐lithiation and transmetalation, is described. Whereas PtBu3 gave rise to α‐arylated Boc‐protected amines, more flexible N‐phenylazole‐based phosphine ligands induced major β‐arylation through migrative cross‐coupling. 相似文献