共查询到20条相似文献,搜索用时 31 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3230-3234
To expand the scope of meta ‐functionalization, a pyrimidine‐based template effective for the formation of β‐aryl aldehydes and ketones, using allyl alcohols, by meta ‐C−H activation of benzylsulfonyl esters is described. In addition, α,β‐unsaturated aldehydes were generated by in situ olefination and deprotection of allyl benzyl ethers. These new functionalizations at the meta ‐position of an arene have also been successfully implemented in benzylphosphonate, phenethyl carbonyl, and phenethylsulfonyl ester scaffolds. Key to these successful new functionalizations is the creation of an electropositive palladium center by accepting the electron cloud from the metal to the energetically low‐lying π‐orbitals of pyrimidine ring, and it favors coordination of allyl alcohol to the metal center. 相似文献
2.
Sabrina I. Kallne Thomas Braun 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(35):9465-9469
An unprecedented reaction pathway for the borylation of SCF3‐containing arenes using [Rh(Bpin)(PEt3)3] (pin=pinacolato) is reported. Catalytic processes were developed and the functionalizations proceed under mild reaction conditions. The C H activations occur with a unique regioselectivity for the position ortho to the SCF3 group, which apparently serves as directing group. Borylated SCF3 compounds can serve as versatile building blocks. 相似文献
3.
Catalytic Borylation of SCF3‐Functionalized Arenes by Rhodium(I) Boryl Complexes: Regioselective CH Activation at the ortho‐Position 下载免费PDF全文
Dipl.‐Chem. Sabrina I. Kalläne Prof. Dr. Thomas Braun 《Angewandte Chemie (International ed. in English)》2014,53(35):9311-9315
An unprecedented reaction pathway for the borylation of SCF3‐containing arenes using [Rh(Bpin)(PEt3)3] (pin=pinacolato) is reported. Catalytic processes were developed and the functionalizations proceed under mild reaction conditions. The C? H activations occur with a unique regioselectivity for the position ortho to the SCF3 group, which apparently serves as directing group. Borylated SCF3 compounds can serve as versatile building blocks. 相似文献
4.
Dr. Nivesh Kumar Dr. Reddy Rajasekhar Reddy Dr. Ahmad Masarwa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8008-8012
An efficient and general method for the chemoselective synthesis of unsymmetrical gem-diborylalkanes is reported. This method is based on a late-stage desymmetrization through nucleophilic “trifluorination”, providing chiral gem-diborylalkanes bearing a trifluoroborate group. The reaction offers a highly modular and diastereoselective approach towards the synthesis of gem-diborylcyclopropanes. The utility of the gem-diborylalkane building blocks was demonstrated by selective post-functionalization of the trifluoroborate group. These functionalizations include inter- and intra- Pd-catalyzed Suzuki–Miyaura coupling reactions. 相似文献
5.
Shingo Kimura Satoshi Kobayashi Takuya Kumamoto Aki Akagi Naomi Sato Tsutomu Ishikawa 《Helvetica chimica acta》2011,94(4):578-591
Towards total synthesis of a series of kinamycin and related antibiotics via common synthetic intermediates, total synthesis of prekinamycin was achieved via Suzuki coupling of naphthaleneboronic acid and bromobenzene derivative, intramolecular Friedel? Crafts reaction of 2‐(naphthalen‐2‐yl)benzoic acid, and diazotization in ten steps from 3,5‐dimethylphenol. Synthetic studies towards kinamycin antibiotics was also examined, and the tetracyclic quinone core for kinamycins was synthesized. Palladium‐catalyzed site‐selective hydroxylation of a benzoic acid derivative with the AB‐D ring part was successfully applied to the selective D‐ring functionalizations. 相似文献
6.
Hypervalent Iodine‐Catalyzed Oxidative Functionalizations Including Stereoselective Reactions 下载免费PDF全文
Hypervalent iodine chemistry is now a well‐established area of organic chemistry. Novel hypervalent iodine reagents have been introduced in many different transformations owing to their mild reaction conditions and environmentally friendly nature. Recently, these reagents have received particular attention because of their applications in catalysis. Numerous hypervalent iodine‐catalyzed oxidative functionalizations such as oxidations of various alcohols and phenols, α‐functionalizations of carbonyl compounds, cyclizations, and rearrangements have been developed successfully. In these catalytic reactions stoichiometric oxidants such as mCPBA or oxone play a crucial role to generate the iodine(III) or iodine(V) species in situ. In this Focus Review, recent developments of hypervalent iodine‐catalyzed reactions are described including some asymmetric variants. Catalytic reactions using recyclable hypervalent iodine catalysts are also covered. 相似文献
7.
Alexandre Hentz Dr. Pascal Retailleau Prof. Dr. Vincent Gandon Dr. Kevin Cariou Dr. Robert H. Dodd 《Angewandte Chemie (International ed. in English)》2014,53(32):8333-8337
Two unprecedented N functionalizations of indoles with ynamides are described. By varying the electron‐withdrawing group on the ynamide nitrogen atom, either Z‐indolo‐etheneamides or indolo‐amidines can be selectively obtained under the same metal‐free reaction conditions. The scope and synthetic potential of these reactions, as well as some mechanistic insights provided by DFT calculations, are reported. 相似文献
8.
Ming Hu Jian‐Hong Fan Yu Liu Xuan‐Hui Ouyang Ren‐Jie Song Jin‐Heng Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(33):9713-9716
A new metal‐free oxidative radical [2+2+1] carbocyclization of benzene‐linked 1,n‐enynes with two C(sp3) H bonds adjacent to the same heteroatom is described. This method achieves two C(sp3) H oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five‐membered carbocyclic hydrocarbons. 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1579-1582
Methods for positionally selective remote C−H functionalizations are in high demand. Herein, we disclose the first heterogeneous ruthenium catalyst for meta ‐selective C−H functionalizations, which enabled remote halogenations with excellent site selectivity and ample scope. The versatile heterogeneous Ru@SiO2 catalyst was broadly applicable and could be easily recovered and reused, which set the stage for the direct fluorescent labeling of purines. In contrast to palladium, rhodium, iridium, or cobalt complexes, solely the ruthenium catalysis manifold provided access to meta ‐halogenated purine derivatives, illustrating the unique power of ruthenium C−H activation catalysis. 相似文献
10.
ZnII‐ and AuI‐Catalyzed Regioselective Hydrative Oxidations of 3‐En‐1‐ynes with Selectfluor: Realization of 1,4‐Dioxo and 1,4‐Oxohydroxy Functionalizations 下载免费PDF全文
Dr. Appaso Mahadev Jadhav Sagar Ashok Gawade Dr. Dhananjayan Vasu Dr. Ramesh B. Dateer Prof. Dr. Rai‐Shung Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):1813-1817
Catalytic 1,4‐dioxo functionalizations of 3‐en‐1‐ynes to (Z)‐ and (E)‐2‐en‐1,4‐dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one‐pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4‐hydroxy‐2‐en‐1‐carbonyl products instead. A cooperative action of pyridine and ZnII assists the hydrolysis of key oxonium intermediate. 相似文献
11.
The imidazo[1,2‐a]pyridines are an important target in organic synthetic chemistry and have attracted critical attention of chemists mainly due to the discovery of the interesting properties exhibited by a great number of imidazo[1,2‐a]pyridine derivatives. Although lots of synthetic methods of imidazo[1,2‐a]pyridines have been developed in the past years, the chemistry community faces continuing challenges to use green reagents, maximize atom economy and enrich the functional group diversity of product. Undoubtedly, with its low cost and lack of environmentally hazardous byproducts, cascade reactions and C?H functionalizations are ideal strategies for this field. In this record we highlight some of our progress toward the goal to synthesis of imidazo[1,2‐a]pyridine derivatives through carbene transformations or C?H functionalizations. 相似文献
12.
Symmetry‐Driven Strategy for the Assembly of the Core Tetracycle of (+)‐Ryanodine: Synthetic Utility of a Cobalt‐Catalyzed Olefin Oxidation and α‐Alkoxy Bridgehead Radical Reaction 下载免费PDF全文
Dr. Masanori Nagatomo Dr. Koji Hagiwara Kengo Masuda Masaki Koshimizu Takahiro Kawamata Yuki Matsui Dr. Daisuke Urabe Prof. Dr. Masayuki Inoue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):222-229
Ryanodine ( 1 ) is a potent modulator of intracellular calcium release channels, designated as ryanodine receptors. The exceptionally complex molecular architecture of 1 comprises a highly oxygenated pentacyclic system with eleven contiguous stereogenic centers, which makes it a formidable target for organic synthesis. We identified the embedded C2‐symmetric tricyclic substructure within 1 . This specific recognition permitted us to design a concise synthetic route to enantiopure tricycle 9 by utilizing a series of pairwise functionalizations. The four tetrasubstituted carbon centers of 9 were effectively constructed by three key reactions, a dearomatizing Diels–Alder reaction, the kinetic resolution of the obtained racemic 14 through asymmetric methanolysis, and the transannular aldol reaction of the eight‐membered diketone 10 . A new combination of cobalt‐catalyzed hydroperoxidation and NfF‐promoted elimination enabled conversion of the hindered olefin of 9 into the corresponding ketone, thus realizing the desymmetrization. Finally, the tetrasubstituted carbon was stereospecifically installed by utilizing the α‐alkoxy bridgehead radical to deliver the core tetracycle 7 with the six contiguous tetrasubstituted carbon centers. Consequently, the present work not only accomplishes efficient assembly of four out of the five fused rings of 1 , but also develops two new powerful methodologies: two‐step ketone formation and bridgehead radical reaction. 相似文献
13.
Ms. Orsolya Tischler Mr. Balázs Tóth Dr. Zoltán Novák 《Chemical record (New York, N.Y.)》2017,17(2):184-199
This account collects the developments and transformations which avoid the utilization of harsh reaction conditions in the field of palladium catalyzed, ortho‐directed C?H activation of aniline derivatives from the first attempts to up‐to‐date results, including the results of our research laboratory. The discussed functionalizations performed under mild conditions include acylation, olefination, arylation, alkylation, alkoxylation reactions. Beside the optimization studies and the synthetic applications mechanistic investigations are also presented. 相似文献
14.
Dr. Hua Zhang Prof. Dr. Shinya Hagihara Prof. Dr. Kenichiro Itami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):16796-16800
The dimethylamino (Me2N) group is arguably the most versatile functional group capable of highly efficient and site‐selective directed aromatic functionalizations at the ortho‐, meta‐, and para‐positions depending on reaction conditions. While the repertoire of Me2N‐directed reactions is growing at a rapid pace, the lack of a general method to transform this group to other functionalities hampers its wider application in organic synthesis. Here we report nickel‐catalyzed C?N borylations of aryl‐ and benzyl‐dimethylamines that permit the conversion of a huge library of largely underutilized Me2N‐containing organic molecules into various functional molecules by taking advantage of the wealth of existing C?B functionalization methods. 相似文献
15.
Martin PichetteDrapeau Janet Bahri Dominik Lichte Lukas J. Gooßen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(3):902-906
In the presence of a bimetallic Pd/Cu system with 1,10‐phenanthroline as the ligand and either air or N‐methylmorpholine N‐oxide as the oxidant, electron‐deficient benzoic acids undergo oxidative decarboxylative coupling with unprotected amines. This operationally simple aniline synthesis is widely applicable with respect to the amine and gives good yields, even on multigram scale. The orthogonality of this reaction to other Pd‐catalyzed cross‐couplings allows the concise synthesis of multisubstituted arenes by sequential C?C, C?Cl, and C?N functionalizations. Mechanistic investigations suggest the intermediacy of a hypervalent Pd species. 相似文献
16.
Hyune-Jea Lee Prof. Dr. Heejin Kim Prof. Dr. Dong-Pyo Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(50):11641-11645
Ibuprofen was prepared from an inactive and inexpensive p-xylene by three-step flow functionalizations through chemoselective metalations of benzyl positions in sequence using an in situ generated LICKOR-type superbase. The flow approach in the microreactor facilitated the comprehensive exploration of over 100 conditions in the first-step reaction by varying concentrations, temperatures, solvents, and equivalents of reagents, enabling optimal conditions to be found with 95 % yield by significantly suppressing the formation of byproducts, followed by the second C−H metalation step in 95 % yield. Moreover, gram-scale synthesis of ibuprofen in the final step was achieved by biphasic flow reaction of solution-phase intermediate with CO2, isolating 2.3 g for 10 min of operation time. 相似文献
17.
Loris Laze Paula Romero Prof. Dr. Irene Bosque Prof. Dr. Jose C. Gonzalez-Gomez 《European journal of organic chemistry》2023,26(6):e202201484
Direct and selective C(sp2)−H/C(sp2)−H cross-dehydrogenative coupling has become a promising strategy to increase molecular complexity with a high atom economy. This study describes an efficient and straightforward protocol for the regioselective C3-H/C3-H cross-coupling of 4-hydroxycoumarin derivatives with quinoxalin-2(1H)-ones, including late-stage modification of natural drugs, promoted by visible light under aerobic conditions at room temperature. With this approach, a wide range of hybrid drug-like molecules were prepared, using air as the terminal oxidant. Remarkably, the C4-OH group at the coumarin ring is essential for the reaction and has been used as a handle for diverse functionalizations of the final products. Moreover, sunlight can promote the reaction under very mild and sustainable conditions, even on a gram scale. Qualitative and semi-quantitative tools were used to demonstrate the greenness advance of this methodology over previously reported ones. Several experiments were conducted to propose a plausible mechanism for this transformation. 相似文献
18.
Enantioselective Organocatalytic Cascade Approach to Different Classes of Benzofused Acetals 下载免费PDF全文
Bruno Matos Paz Dr. Lydia Klier Line Næsborg Vibeke Henriette Lauridsen Prof. Dr. Frank Jensen Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16810-16818
A novel enantioselective organocatalytic strategy is presented for the synthesis of tetrahydrofurobenzofuran and methanobenzodioxepine natural product core structures. The strategy is based on a pair of divergent reaction pathways in which hydroxyarenes react with γ‐keto‐α,β‐unsaturated aldehydes, catalyzed by a chiral secondary amine. One reaction pathway, which leads to chiral 5,5‐fused acetals with two stereocenters—the tetrahydrofurobenzofuran scaffolds—proceeds in moderate yields and up to 96 % ee. The other reaction pathway provides 5,6‐bridged methanobenzodioxepine scaffolds with three stereocenters in moderate to good yields and up to 95 % ee. The reaction is remarkable as it can proceed with catalyst loadings as low as 0.25 mol %, providing one of the highest known turnover numbers in iminium ion catalysis. Furthermore, the hemiacetal tetrahydrofurobenzofuran can undergo functionalizations including reduction, oxidation, and allylation. Finally, the effects involved in the substrate control for the divergent pathways, based on both experimental and computational studies, have been investigated. A model involving steric, electronic and stereoelectronic interactions is discussed to rationalize the observed selectivities. 相似文献
19.
The data on nucleophilic substitution reactions of hydrogen in 6,8‐dimethylpyrimido[4,5‐c]pyridazine‐5,7(6H,8H)‐dione, its 3‐chloride, N2‐oxide and some other derivatives are reviewed. All these compounds possess a remarkable ability to undergo not only simple functionalizations but also tandem and cascade transformations leading to annelation of various heterocyclic rings. 相似文献
20.
Dr. Benudhar Punji Weifeng Song Grigory A. Shevchenko Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(32):10605-10610
Inexpensive cobalt catalysts derived from N‐heterocylic carbenes (NHC) allowed efficient catalytic C? H bond arylations on heteroaryl‐substituted arenes with widely available aryl chlorides, which set the stage for the preparation of sterically hindered tri‐ortho‐substituted biaryls. Likewise, challenging direct alkylations with β‐hydrogen‐containing primary and even secondary alkyl chlorides proceeded on pyridyl‐ and pyrimidyl‐substituted arenes and heteroarenes. The cobalt‐catalyzed C? H bond functionalizations occurred efficiently at ambient reaction temperature with excellent levels of site‐selectivities and ample scope. Mechanistic studies highlighted that electron‐deficient aryl chlorides reacted preferentially, while the arenes kinetic C? H bond acidity was found to largely govern their reactivity. 相似文献