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1.
Ming-Xing Song Guo-Qing Xi Hao-Yuan Chi Ke-Chuan He Peng Lü Zheng-Kun Qin Yong-Ling Zhang Shi-Quan Lü Hong-Jie Zhang 《应用有机金属化学》2020,34(5):e5525
A series of heterocyclic Ir(III) complexes used in organic light-emitting diode (OLED) materials with low-efficiency roll-off performance have been studied theoretically. Their electronic structures, spectral properties, and their application value in OLEDs are discussed. The geometries, electronic structures, lowest-lying singlet absorptions, and triplet emissions of (dmdppr-dmp)2Ir(dibm), and the theoretically designed models of (dmdppr-dmp)2Ir(acac), (dmdppr-dmp)2Ir(tpip), (dmdppr-Fdmp)2Ir(dibm), (dmdppr-Fdmp)2Ir(acac), and (dmdppr-Fdmp)2Ir(tpip) were investigated with density-functional-theory-based approaches, where dibm denotes 2,6-dimethy-3,5-heptanedionato-κ2-O,O′, acac denotes acetylacetonate, and tpip denotes tetraphenylimido-diphosphinate. 相似文献
2.
Jun‐Long Li Cai‐Zhen Yue Peng‐Qiao Chen You‐Cai Xiao Prof. Dr. Ying‐Chun Chen 《Angewandte Chemie (International ed. in English)》2014,53(21):5449-5452
Catalytic asymmetric Friedel–Crafts alkylation is a powerful protocol for constructing a chiral C(sp2)? C(sp3) bond. Most previous examples rely on LUMO activation of the electrophiles using chiral catalysts with subsequent attack by electron‐rich arenes. Presented herein is an alternative strategy in which the HOMO of the aromatic π system of 2‐furfuryl ketones is raised through the formation of a formal trienamine species using a chiral primary amine. Exclusive regioselective alkylation at the 5‐position occurred with alkylidenemalononitriles, and high reactivity and excellent enantioselectivity (up to 95 % ee) was obtained by this remote activation. 相似文献
3.
《Journal of heterocyclic chemistry》2018,55(9):2055-2060
A straightforward approach for the regioselective synthesis of highly functionalized pyrazolo[5,1‐b]purine from the annulation of 6‐bromo‐3‐cyano‐2‐(ethylthio)‐5‐methyl‐7‐oxo‐6,7‐dihydropyrazolo[1,5‐a]pyrimidine with thiourea as a bisnucleophilic reagent under reflux condition in CH3CN in the presence of Et3N has been developed. The N‐alkylation of the synthesis compound was also accomplished. The true regioisomer was determined by 2D‐NOESY NMR spectroscopy, as well. 相似文献
4.
Guang‐Yao Ran Xing‐Xing Yang Jing‐Fei Yue Wei Du Ying‐Chun Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9308-9312
An atom‐economic and highly efficient vinylogous umpolung strategy is developed for deconjugated carbonyl compounds, which generate electron‐deficient π‐allylpalladium complexes with Pd(OAc)2 under ligand‐free conditions. In cooperation with a chiral‐phosphonium‐based phase‐transfer catalyst, the asymmetric direct oxidative allylic alkylations of 3‐substituted oxindoles are furnished under O2 atmosphere. The γ‐ or even remote ?‐regioselective alkylation products, with substantial substituents, are delivered with excellent enantioselectivity, and can be further used to access diverse chiral spirocyclic architectures effectively. The Mukaiyama dienol silyl ether can be utilized similarly, indicating that the current active π‐allylpalladium species results from tautomerization of the PdII‐dienolate intermediate. 相似文献
5.
Srinivas Tekkam Joseph L. Johnson Subash C. Jonnalagadda Venkatram R. Mereddy 《Journal of heterocyclic chemistry》2013,50(4):969-972
A novel methodology for the efficient synthesis of [2.2.1] heterobicyclic pyroglutamates has been described. The key synthetic steps involve alkylation of amino acid‐derived iminoesters with Baylis‐Hillman bromide, RhCl3‐catalyzed exocyclic olefin isomerization, diastereoselective dihydroxylation, and regioselective lactonization. All the compounds were evaluated for their cytotoxicity using multiple myeloma cancer cell lines RPMI 8226. 相似文献
6.
Full Functionalization of the Imidazole Scaffold by Selective Metalation and Sulfoxide/Magnesium Exchange
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Christoph Sämann Estibaliz Coya Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2014,53(5):1430-1434
A simple, flexible, and straightforward method for the functionalization of all the positions of the imidazole heterocycle through regioselective arylations, allylations, acylations, and additions to aldehydes is disclosed. Starting from the readily available key imidazole 1 , highly functionalized imidazole derivatives have been synthesized in a regioselective manner from directed metalations and a sulfoxide/magnesium exchange. Moreover, the selective N3‐alkylation followed by deprotection of N1 (trans‐N‐alkylation) allows the regioselective N‐alkylation of complex imidazoles. 相似文献
7.
Peng Chen Zhi‐Chao Chen Yue Li Qin Ouyang Wei Du Ying‐Chun Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4076-4080
Auto‐tandem catalysis (ATC), in which a single catalyst promotes two or more mechanistically different reactions in a cascade pattern, provides a powerful strategy to prepare complex products from simple starting materials. Reported here is an unprecedented auto‐tandem cooperative catalysis (ATCC) for Morita–Baylis–Hillman carbonates from isatins and allylic carbonates using a simple Pd(PPh3)4 precursor. Dissociated phosphine generates phosphorus ylides and the Pd leads to π‐allylpalladium complexes, and they undergo a γ‐regioselective allylic–allylic alkylation reaction. Importantly, a cascade intramolecular Heck‐type coupling proceeds to finally furnish spirooxindoles incorporating a 4‐methylene‐2‐cyclopentene motif. Experimental results indicate that both Pd and phosphine play crucial roles in the catalytic Heck reaction. In addition, the asymmetric versions with either a chiral phosphine or chiral auxiliary are explored, and moderate results are obtained. 相似文献
8.
C‐Selective and Diastereoselective Alkyl Addition to β,γ‐Alkynyl‐α‐imino Esters with Zinc(II)ate Complexes
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Dr. Manabu Hatano Kenji Yamashita Mai Mizuno Orie Ito Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2015,54(9):2707-2711
Since umpolung α‐imino esters contain three electrophilic centers, regioselective alkyl addition with traditional organometallic reagents has been a serious problem in the practical synthesis of versatile chiral α‐amino acid derivatives. An unusual C‐alkyl addition to α‐imino esters using a Grignard reagent (RMgX)‐derived zinc(II)ate was developed. Zinc(II)ate complexes consist of a Lewis acidic [MgX]+ moiety, a nucleophilic [R3Zn]? moiety, and 2 [MgX2]. Therefore, the ionically separated [R3Zn]? selectively attacks the imino carbon atom ,which is most strongly activated by chelation of [MgX]+. In particular, chiral β,γ‐alkynyl‐α‐imino esters can strongly promote highly regio‐ and diastereoselective C‐alkylation because of structural considerations, and the corresponding optically active α‐quaternary amino acid derivatives are obtained within 5 minutes in high to excellent yields. 相似文献
9.
Philip Andreetta Dr. Robert T. Martin Charafa Souilah Dr. Ángel Rentería-Gómez Dr. Zhihui Song Yas Khorramshahi Bayat Dr. Sergei Ivlev Prof. Dr. Osvaldo Gutierrez Prof. Dr. Alicia Casitas 《Angewandte Chemie (International ed. in English)》2023,62(46):e202310129
Here, we report the development of cobalt(I)-catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3-dicarbonyl compounds. A family of well-defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3)Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3)Cl] (dppp=1,3-Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt-catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle. 相似文献
10.
Jiang L Lei Q Huang X Cui HL Zhou X Chen YC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(34):9489-9493
A Lewis base assisted Brønsted base catalysis (LBABB) strategy is applied for direct asymmetric vinylogous alkylation of allylic sulfones with Morita–Baylis–Hillman (MBH) carbonates, in which a strong Brønsted base, tert‐butoxy anion, generated in situ from a tertiary amine catalyst and MBH carbonate, is crucial in activating unstabilized nucleophiles. The γ‐regioselective alkylation products were obtained with good to excellent enantiomeric excess values when catalyzed by a modified cinchona alkaloid. 相似文献
11.
Catalytic and Atom‐Economic C
−C
Bond Formation: Alkyl Tantalum Ureates for Hydroaminoalkylation
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Rebecca C. DiPucchio Dr. Sorin‐Claudiu Roşca Prof. Laurel L. Schafer 《Angewandte Chemie (International ed. in English)》2018,57(13):3469-3472
Atom‐economic and regioselective C ?C bond formation has been achieved by rapid C?H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH2SiMe3)3Cl2, and a ureate N,O‐chelating‐ligand salt gives catalytic systems prepared in situ that can realize high yields of β‐alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C?H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration. 相似文献
12.
The mechanisms of iron‐catalyzed regioselective anti‐Markovnikov addition of C‐H bonds in the aromatic ketones to alkenes are studied using Density Functional Theory (DFT) calculations with the B3LYP‐D3 method. Our results show that the overall catalytic cycle includes the initial generation of aromatic ketone C‐H activation, the coordination and insertion of a styrene, and finally C‐C reductive elimination. Two different alkylation products are obtained through the linear or branched formation via several different paths. The formation of the linear product is energetically favorable over that of the branched product, which is in agreement with the experimental observation. The rate‐limiting step for the whole catalytic cycle to obtain the main linear product is the reductive elimination step where the Gibbs free energy in solvent THF ΔGsol is 13.5 kcal/mol computed using the SMD method. 相似文献
13.
A novel stereoselective SN2′ alkylation reaction sequence of the γ,δ-epoxy α,β-unsaturated ester system has been developed which involves a regioselective substitution reaction with chloride ions at the γ-position and a subsequent SN2′ alkylation reaction of the resulting γ-chloro-δ-hydroxy derivatives with a R3Al-CuCN reagent. The new methodology was demonstrated to be applicable to a variety of substrates and to provide various δ-hydroxy-α-alkyl-β,γ-unsaturated esters including those bearing a quaternary asymmetric carbon atom at the α-position in a highly stereoselective manner and high yields. 相似文献
14.
Dipl.‐Chem. Dipl.‐Ing. André P. Dieskau Dipl.‐Chem. Michael S. Holzwarth Prof. Dr. Bernd Plietker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2423-2429
We present herein a versatile and broadly applicable Fe‐catalyzed regioselective alkoxy allylation of activated double bonds. Substituted allylic carbonates are converted into the corresponding σ‐enyl Fe complexes by reaction with Bu4N[Fe(CO)3(NO)] (TBAFe) at 30 °C. The liberated alkoxide adds to an activated double bond with the generation of a C‐nucleophile, which is trapped by the σ‐enyl Fe complex in a regioselective manner. Alternatively, the alkoxide acts as a base in deprotonating an external pronucleophile, which undergoes Michael addition. The method is characterized by a broad functional group tolerance, mild reaction conditions, low catalyst loadings, and high regioselectivities in favor of the ipso‐substitution product. 相似文献
15.
Umpolung Reactions of α‐Imino Esters: Useful Methods for the Preparation of α‐Amino Acid Frameworks
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This paper summarizes our recent efforts toward the development of tandem reactions utilizing umpolung reactions of α‐imino esters. A highly diastereoselective tandem N‐alkylation–Mannich reaction of α‐imino esters was developed. A tandem N‐alkylation–addition reaction of α‐imino esters derived from ethyl glyoxylate with various aldehydes proceeded to give 1,2‐amino alcohols. The same reaction also proceeded efficiently using a novel flow system comprising two connected microreactors. Novel syntheses of α‐quaternary alkynyl amino esters and allenoates were developed through the use of umpolung N‐addition to β,γ‐alkynyl α‐imino esters, followed by regioselective acylation. In addition, a highly regioselective tandem N‐alkylation–vinylogous aldol reaction of β,γ‐alkenyl α‐imino esters was discovered. N‐Alkylation of α‐iminophosphonates followed by a Horner–Wadsworth–Emmons reaction with aldehydes occurred to afford enamines, which can be used in a four‐component coupling reaction with methyl vinyl ketone. α‐N‐Acyloxyimino esters served as highly efficient substrates for the N,N,C‐trialkylation reaction to introduce various nucleophiles at the imino nitrogen and carbon atoms. 相似文献
16.
Madhu Sudan Manna Seok Yeol Yoo Mohammed Sharique Hyoju Choi Bimal Pudasaini Prof. Dr. Mu-Hyun Baik Prof. Dr. Uttam K. Tambar 《Angewandte Chemie (International ed. in English)》2023,62(35):e202304848
We report a copper-catalyzed, regioselective, and stereospecific alkylation of unbiased internal allylic carbonates with functionalized alkyl and aryl Grignard reagents. The reactions exhibit high stereospecificity and regioselectivity for either SN2 or SN2′ products under two sets of copper-catalyzed conditions, which enables the preparation of a broad range of products with E-alkene selectivity. Density functional theory calculations reveal the origins of the regioselectivity based on the different behaviors of homo- and heterocuprates. 相似文献
17.
The strategies described here have permitted the synthesis of a series of 4-aminoquinoline antimalarials. Substantive improvements over previous syntheses include nucleophilic substitution with neat amine rather than in phenol, regioselective reductive alkylation to convert the terminal primary amine (12a–20a) on the diaminoalkane side chain to a diethylamino group, and purification by column chromatography with basic alumina. The 1H nmr spectra obtained after regioselective reductive alkylation with sodium borodeuteride (in comparison with sodium borohydride) demonstrated that this reductive alkylation proceeds via formation and subsequent reduction of the corresponding diamides in situ. 相似文献
18.
Miguel Peña‐López M. Montserrat Martínez Dr. Luis A. Sarandeses Prof. Dr. José Pérez Sestelo Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):910-916
The first total synthesis of (+)‐neomarinone has been achieved by following a concise and convergent route using methyl (R)‐lactate and (R)‐3‐methylcyclohexanone as chiral building blocks. Key steps of the synthesis are the stereocontrolled formation of the two quaternary stereocenters by diastereoselective 1,4‐conjugate addition and enolate alkylation reactions, and the construction of the furanonaphthoquinone skeleton by regioselective Diels–Alder reaction between a 1,3‐bis(trimethylsilyloxy)‐1,3‐diene and a bromoquinone. The synthesis proves the relative and absolute stereochemistry of natural neomarinone. 相似文献
19.
Hashem Sharghi Mona Hosseini‐Sarvari Fatemeh Moeini Reza Khalifeh AlirezaSalimi Beni 《Helvetica chimica acta》2010,93(3):435-449
A safe, efficient, and improved procedure for the regioselective synthesis of 1‐(2‐hydroxyethyl)‐1H‐1,2,3‐triazole derivatives under ambient conditions is described. Terminal alkynes reacted with oxiranes and NaN3 in the presence of a copper(I) catalyst, which is prepared by in situ reduction of the copper(II) complex 4 with ascorbic acid, in H2O. The regioselective reactions exclusively gave the corresponding 1,4‐disubstituted 1H‐1,2,3‐triazoles in good to excellent yields. This procedure avoids the handling of organic azides as they are generated in situ, making this already powerful click process even more user‐friendly and safe. The remarkable features of this protocol are high yields, very short reaction times, a cleaner reaction profile in an environmentally benign solvent (H2O), its straightforwardness, and the use of nontoxic catalysts. Furthermore, the catalyst could be recovered and recycled by simple filtration of the reaction mixture and reused for ten consecutive trials without significant loss of catalytic activity. No metal‐complex leaching was observed after the consecutive catalytic reactions. 相似文献
20.
The use of 1-adamantyl bromomethyl ketone, under phase transfer catalysis conditions permits the regioselective N1 alkylation of uracil and thymine,the N1,N3 dialkyl derivatives. The observed selectivity is discussed in relaxation with the structure of the alkylating agent. 相似文献