共查询到20条相似文献,搜索用时 15 毫秒
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Haizea Echave Dr. Rosa López Prof. Dr. Claudio Palomo 《Angewandte Chemie (International ed. in English)》2016,55(10):3364-3368
The first enantioselective direct cross‐aldol reaction of α‐keto amides with aldehydes, mediated by a bifunctional ureidopeptide‐based Brønsted base catalyst, is described. The appropriate combination of a tertiary amine base and an aminal, and urea hydrogen‐bond donor groups in the catalyst structure promoted the exclusive generation of the α‐keto amide enolate which reacted with either non‐enolizable or enolizable aldehydes to produce highly enantioenriched polyoxygenated aldol adducts without side‐products resulting from dehydration, α‐keto amide self‐condensation, aldehyde enolization, and isotetronic acid formation. 相似文献
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Dipl.‐Chem. Sadiya Raja Dr. Winai Ieawsuwan Dr. Vadim Korotkov Prof. Magnus Rueping 《化学:亚洲杂志》2012,7(10):2361-2366
A Brønsted acid‐catalyzed asymmetric Nazarov cyclization of acyclic α‐alkoxy dienones has been developed. The reaction offers access to chiral cyclopentenones in a highly enantioselective manner. The reaction is complementary to our previously reported Brønsted acid‐catalyzed electrocyclization reactions, which provided differently substituted optically active cyclopentenones with a fused tetrahydropyrane ring in good yields and with excellent enantioselectivities. 相似文献
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Lei Yang Dr. Qiming Zhu Shengmei Guo Bo Qian Chungu Xia Hanmin Huang Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1638-1645
A cooperative catalytic system established by the combination of an iron salt and a chiral Brønsted acid has proven to be effective in the asymmetric Friedel–Crafts alkylation of indoles with β‐aryl α′‐hydroxy enones. Good to excellent yields and enatioselectivities were observed for a variety of α′‐hydroxy enones and indoles, particularly for the β‐aryl α′‐hydroxy enones bearing an electron‐withdrawing group at the para position of the phenyl ring (up to 90 % yield and 91 % ee). The proton of the chiral Brønsted acid, the Lewis acid activation site, as well as the inherent basic site for the hydrogen‐bonding interaction of the Brønsted acid are responsible for the high catalytic activities and enantioselectivities of the title reaction. A possible reaction mechanism was proposed. The key catalytic species in the catalytic system, the phosphate salt of FeIII, which was thought to be responsible for the high activity and good enantioselectivity, was then confirmed by ESIMS studies. 相似文献
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Brønsted Acid Enabled Nickel‐Catalyzed Hydroalkenylation of Aldehydes with Styrene and its Derivatives
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Xing‐Wang Han Tao Zhang Yan‐Long Zheng Wei‐Wei Yao Jiang‐Fei Li You‐Ge Pu Prof. Dr. Mengchun Ye Qi‐Lin Zhou 《Angewandte Chemie (International ed. in English)》2018,57(18):5068-5071
A Brønsted acid enabled nickel‐catalyzed hydroalkenylation of aldehydes and styrene derivatives has been developed. The Brønsted acid acts as a proton shuttle to transfer a proton from the alkene to the aldehyde, thereby leading to an economical and byproduct‐free coupling. A series of synthetically useful allylic alcohols were obtained through one‐step reactions from readily available styrene derivatives and aliphatic aldehydes in up to 88 % yield and with high linear selectivity. 相似文献
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Caitlan E. Ayala Dr. Nitin S. Dange Prof. Dr. Rendy Kartika 《Angewandte Chemie (International ed. in English)》2015,54(15):4641-4645
A new method which enables carbon–carbon bond formation at the α′‐position of silylenol ethers by using catalytic amounts of pyridinium triflate is reported. This chemistry successfully produces, structurally challenging, highly substituted indole‐containing silylenol ethers in excellent yields with complete regiocontrol, presumably through silyloxyallyl cation intermediates. Despite the use of Brønsted acid, the silylenol ether moiety does not undergo protodesilylation, thus underscoring the very mild reaction conditions. 相似文献
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Enantioselective α‐Alkylation of Aldehydes by Photoredox Organocatalysis: Rapid Access to Pharmacophore Fragments from β‐Cyanoaldehydes
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Eric R. Welin Dr. Alexander A. Warkentin Dr. Jay C. Conrad Prof. Dr. David W. C. MacMillan 《Angewandte Chemie (International ed. in English)》2015,54(33):9668-9672
The combination of photoredox catalysis and enamine catalysis has enabled the development of an enantioselective α‐cyanoalkylation of aldehydes. This synergistic catalysis protocol allows for the coupling of two highly versatile yet orthogonal functionalities, allowing rapid diversification of the oxonitrile products to a wide array of medicinally relevant derivatives and heterocycles. This methodology has also been applied to the total synthesis of the lignan natural product (?)‐bursehernin. 相似文献
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Direct N‐Glycofunctionalization of Amides with Glycosyl Trichloroacetimidate by Thiourea/Halogen Bond Donor Co‐Catalysis
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Dr. Yusuke Kobayashi Yuya Nakatsuji Shanji Li Dr. Seiji Tsuzuki Prof. Dr. Yoshiji Takemoto 《Angewandte Chemie (International ed. in English)》2018,57(14):3646-3650
Using a halogen bond (XB) donor and Schreiner's thiourea as cooperative catalysts, various amides, including the asparagine residues of several peptides, were directly coupled with glycosyl trichloroacetimidates to give unique N‐acylorthoamides in good yields. Synthetic applications of N‐acylorthoamides, including rearrangement to the corresponding β‐N‐glycoside, were also demonstrated. 相似文献
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Antonia Mielgo Dr. Irene Velilla Claudio Palomo Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(25):7496-7502
In the presence of p‐nitrobenzoic acid, the O‐nitroso aldol reaction of nitrosobenzene with enolisable aldehydes may be promoted by commercially available α,α‐diphenylprolinol trimethylsilyl ether. The reaction proceeds with good yields and essentially complete enantioselectivity, with catalyst loadings in the 5–10 mol % range. The resulting α‐oxyaldehyde adducts may be transformed in situ into α‐oxyimines, which provide 1,2‐amino alcohols upon treatment with Grignard reagents, in good overall yield (45–59 %) and with typical diastereomeric ratios ≥95:5. 相似文献
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Aminomethylation of Enals through Carbene and Acid Cooperative Catalysis: Concise Access to β2‐Amino Acids
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Dr. Jianfeng Xu Xingkuan Chen Dr. Ming Wang Pengcheng Zheng Bao‐An Song Prof. Dr. Yonggui Robin Chi 《Angewandte Chemie (International ed. in English)》2015,54(17):5161-5165
A convergent, organocatalytic asymmetric aminomethylation of α,β‐unsaturated aldehydes by N‐heterocyclic carbene (NHC) and (in situ generated) Brønsted acid cooperative catalysis is disclosed. The catalytically generated conjugated acid from the base plays dual roles in promoting the formation of azolium enolate intermediate, formaldehyde‐derived iminium ion (as an electrophilic reactant), and methanol (as a nucleophilic reactant). This redox‐neutral strategy is suitable for the scalable synthesis of enantiomerically enriched β2‐amino acids bearing various substituents. 相似文献
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Catalytic Asymmetric Piancatelli Rearrangement: Brønsted Acid Catalyzed 4π Electrocyclization for the Synthesis of Multisubstituted Cyclopentenones
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Dr. Yunfei Cai Dr. Yurong Tang Prof. Dr. Magnus Rueping 《Angewandte Chemie (International ed. in English)》2016,55(45):14126-14130
The first catalytic asymmetric Piancatelli reaction is reported. Catalyzed by a chiral Brønsted acid, the rearrangement of a wide range of furylcarbinols with a series of aniline derivatives provides valuable aminocyclopentenones in high yields as well as excellent enantioselectivities and diastereoselectivities. The high value of the aza‐Piancatelli rearrangement was demonstrated by the synthesis of a cyclopentane‐based hNK1 antagonist analogue. 相似文献
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Catalytic Enantioselective Synthesis of α‐Chiral Azaheteroaryl Ethylamines by Asymmetric Protonation
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Dr. Chao Xu Calum W. Muir Dr. Andrew G. Leach Dr. Alan R. Kennedy Dr. Allan J. B. Watson 《Angewandte Chemie (International ed. in English)》2018,57(35):11374-11377
The direct enantioselective synthesis of chiral azaheteroaryl ethylamines from vinyl‐substituted N‐heterocycles and anilines is reported. A chiral phosphoric acid (CPA) catalyst promotes dearomatizing aza‐Michael addition to give a prochiral exocyclic aryl enamine, which undergoes asymmetric protonation upon rearomatization. The reaction accommodates a broad range of N‐heterocycles, nucleophiles, and substituents on the prochiral centre, generating the products in high enantioselectivity. DFT studies support a facile nucleophilic addition based on catalyst‐induced LUMO lowering, with site‐selective, rate‐limiting, intramolecular asymmetric proton transfer from the ion‐paired prochiral intermediate. 相似文献
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Enantioselective Formal [3+2] Cycloaddition of Epoxides with Imines under Brønsted Base Catalysis: Synthesis of 1,3‐Oxazolidines with Quaternary Stereogenic Center
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Dr. Azusa Kondoh Shiori Akahira Masafumi Oishi Prof. Dr. Masahiro Terada 《Angewandte Chemie (International ed. in English)》2018,57(21):6299-6303
The formal [3+2] cycloaddition of epoxides and unsaturated compounds is a powerful methodology for the synthesis of densely functionalized five‐membered heterocyclic compounds containing oxygen. Described is a novel enantioselective formal [3+2] cycloaddition of epoxides under Brønsted base catalysis. The bis(guanidino)iminophosphorane as a chiral organosuperbase catalyst enabled the enantioselective reaction of β,γ‐epoxysulfones with imines, owing to its strong basicity and high stereocontrolling ability, to provide enantioenriched 1,3‐oxazolidines having two stereogenic centers, including a quaternary one, in a highly diastereo‐ and enantioselective manner. 相似文献
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Ureidopeptide‐Based Brønsted Bases: Design,Synthesis and Application to the Catalytic Enantioselective Synthesis of β‐Amino Nitriles from (Arylsulfonyl)acetonitriles
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Dr. Saioa Diosdado Dr. Rosa López Prof. Dr. Claudio Palomo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6526-6531
The addition of cyanoalkyl moieties to imines is a very attractive method for the preparation of β‐amino nitriles. We present a highly efficient organocatalytic methodology for the stereoselective synthesis of β‐amino nitriles, in which the key to success is the use of ureidopeptide‐based Brønsted base catalysts in combination with (arylsulfonyl)acetonitriles as synthetic equivalents of the acetonitrile anion. The method gives access to a variety of β‐amino nitriles with good yields and excellent enantioselectivities, and broadens the stereoselective Mannich‐type methodologies available for their synthesis. 相似文献