3530-36-7Relevant academic research and scientific papers
Acid- And base-switched palladium-catalyzed γ-C(sp3)-H alkylation and alkenylation of neopentylamine
Zhang, Jinquan,Zhang, Shuaizhong,Zou, Hongbin
supporting information, p. 3466 - 3471 (2021/05/31)
The functionalization of remote unactivated C(sp3)-H and the reaction selectivity are among the core pursuits for transition-metal catalytic system development. Herein, we report Pd-catalyzed γ-C(sp3)-H-selective alkylation and alkenylation with removable 7-azaindole as a directing group. Acid and base were found to be the decisive regulators for the selective alkylation and alkenylation, respectively, on the same single substrate under otherwise the same reaction conditions. Various acrylates were compatible for the formation of C(sp3)-C(sp3) and C(sp3)-C(sp2) bonds. The alkenylation protocol could be further extended to acrylates with natural product units and α,β-unsaturated ketones. The preliminary synthetic manipulation of the alkylation and alkenylation products demonstrates the potential of this strategy for structurally diverse aliphatic chain extension and functionalization. Mechanistic experimental studies showed that the acidic and basic catalytic transformations shared the same six-membered dimer palladacycle.
Rational Design of Single-Chain Polymeric Nanoparticles That Kill Planktonic and Biofilm Bacteria
Nguyen, Thuy-Khanh,Lam, Shu Jie,Ho, Kitty K. K.,Kumar, Naresh,Qiao, Greg G.,Egan, Suhelen,Boyer, Cyrille,Wong, Edgar H. H.
, p. 237 - 248 (2017/04/21)
Infections caused by multidrug-resistant bacteria are on the rise and, therefore, new antimicrobial agents are required to prevent the onset of a postantibiotic era. In this study, we develop new antimicrobial compounds in the form of single-chain polymeric nanoparticles (SCPNs) that exhibit excellent antimicrobial activity against Gram-negative bacteria (e.g., Pseudomonas aeruginosa) at micromolar concentrations (e.g., 1.4 μM) and remarkably kill ≥99.99% of both planktonic cells and biofilm within an hour. Linear random copolymers, which comprise oligoethylene glycol (OEG), hydrophobic, and amine groups, undergo self-folding in aqueous systems due to intramolecular hydrophobic interactions to yield these SCPNs. By systematically varying the hydrophobicity of the polymer, we can tune the extent of cell membrane wall disruption, which in turn governs the antimicrobial activity and rate of resistance acquisition in bacteria. We also show that the incorporation of OEG groups into the polymer design is essential in preventing complexation with proteins in biological medium, thereby maintaining the antimicrobial efficacy of the compound even in in vivo mimicking conditions. In comparison to the last-resort antibiotic colistin, our lead agents have a higher therapeutic index (by ca. 2-3 times) and hence better biocompatibility. We believe that the SCPNs developed here have potential for clinical applications and the information pertaining to their structure-activity relationship will be valuable toward the general design of synthetic antimicrobial (macro)molecules.
Zirconocene-catalyzed direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1:1 ratio under solvent-free conditions
Tang, Zhi,Jiang, Qiutao,Peng, Lifen,Xu, Xinhua,Li, Jie,Qiu, Renhua,Au, Chak-Tong
supporting information, p. 5396 - 5402 (2017/11/22)
A highly efficient way for the direct (trans)esterification of acyl acids (esters) and alcohols in a strict 1:1 ratio using a zirconocene complex (1, 1 mol%), a strong Lewis acid of good water tolerance, as a catalyst under solvent-free conditions has been developed. A wide range of acid and alcohol (esters) substrates undergo (trans)esterification to produce carboxylic ester motifs in moderate to good or excellent yields with good functional tolerance, such as that towards C-Br as well as CC and CC bonds. And complex 1 can be recycled six times without showing a significant decline in catalytic efficiency. It was demonstrated that cyclandelate, which is used to treat high blood pressure as well as heart and blood-vessel diseases, can be directly synthesized on a gram scale with 81% yield (6.70 g) using complex 1.
Heterobimetallic dinuclear lanthanide alkoxide complexes as acid-base difunctional catalysts for transesterification
Zeng, Ruijie,Sheng, Hongting,Zhang, Yongcang,Feng, Yan,Chen, Zhi,Wang, Junfeng,Chen, Man,Zhu, Manzhou,Guo, Qingxiang
, p. 9246 - 9252 (2014/12/11)
A practical lanthanide(III)-catalyzed transesterification of carboxylic esters, weakly reactive carbonates, and much less-reactive ethyl silicate with primary and secondary alcohols was developed. Heterobimetallic dinuclear lanthanide alkoxide complexes [Ln2Na8{(OCH2CH2NMe2)}12(OH)2] (Ln = Nd (I), Sm (II), and Yb (III)) were used as highly active catalysts for this reaction. The mild reaction conditions enabled the transesterification of various substrates to proceed in good to high yield. Efficient activation of transesterification may be endowed by the above complexes as cooperative acid-base difunctional catalysts, which is proposed to be responsible for the higher reactivity in comparison with simple acid/base catalysts.
Selective acylation of the phenolic hydroxyl of (hydroxyalkyl)phenols by using vinyl carboxylates as acyl donors in the presence of rubidium fluoride
Miyazawa, Toshifumi,Yamamoto, Masato,Danjo, Hiroshi
, p. 1351 - 1354 (2013/10/01)
Highly selective acylation of the phenolic hydroxy group can be achieved with (hydroxyalkyl)phenols carrying both alcoholic and phenolic hydroxyls by the use of vinyl carboxylates as acyl donors in the presence of rubidium fluoride.
Hypervalent (tert-butylperoxy)iodanes generate iodine-centered radicals at room temperature in solution: Oxidation and deprotection of benzyl and allyl ethers, and evidence for generation of α-oxy carbon radicals
Ochiai, Masahito,Ito, Takao,Takahashi, Hideo,Nakanishi, Akinobu,Toyonari, Mika,Sueda, Takuya,Goto, Satoru,Shiro, Motoo
, p. 7716 - 7730 (2007/10/03)
1-(tert-Butylperoxy)-1,2-benziodoxol-3(1H)-one (1a) oxidizes benzyl and allyl ethers to the esters at room temperature in benzene or cyclohexane in the presence of alkali metal carbonates. Since this reaction is compatible with other protecting groups such as MOM, THP, and TBDMS ethers, and acetoxy groups, and because esters are readily hydrolyzed under basic conditions, this new method provides a convenient and effective alternative to the usual reductive deprotection. Oxidation with 1a occurs readily with C-H bonds activated by both enthalpic effects (benzylic, allylic, and propargylic C-H bonds) and/or polar effects (α-oxy C-H bonds), generating α-oxy carbon-centered radicals, which can be detected by nitroxyl radical trapping. Measurement of the relative rates of oxidation for a series of ring-substituted benzyl n-butyl ethers 2d and 2p-s indicated that electron-releasing groups such as p-MeO and p-Me groups increase the rate of oxidation, and Hammett correlation of the relative rate factors with the σ+ constants of substituents afforded the reaction constant ρ+ = -0.30. The large value of the isotope effect obtained for the oxidation of benzyl n-butyl ether 2d (k(H)/k(D) = 12-14) indicates that the rate-determining step of the reactions probably involves a high degree of benzylic C-H bond breaking. The effects of molecular dioxygen were examined, and the mechanism involving the intermediacy of the tert-butylperoxy acetal 5 and/or the hydroperoxy acetal 32 is proposed. Particularly noteworthy is the finding that (tert-butylperoxy)iodane 1a can generate the tert-butylperoxy radical and the iodine-centered radical 33a, even at room temperature in solution, via homolytic bond cleavage of the hypervalent iodine(III)-peroxy bond.
The 'Baylis - Hillman reaction' mechanism and applications revisited
Fort, Yves,Berthe, Marie Christine,Caubere, Paul
, p. 6371 - 6384 (2007/10/02)
It is shown that reaction of aryl, benzyl, alkyl and functionalised alkyl acrylic esters with benzaldehyde, in the presence of 1,4-diazabicyclo[2.2.2] octane, strongly depends upon the electronic and steric effects of the ester part. This influence is also observed in condensation of furfuraldehyde. Moreover, for the first time, it is shown that the overall condensation is equilibrated.
SYNTHESIS OF ACRYLIC ESTERS BY LIPASE
Ikeda, Isao,Tanaka, Jun,Suzuki, Kimihiro
, p. 6865 - 6866 (2007/10/02)
Various acrylic esters were synthesized by the transesterification of vinyl acrylate with various alcohols.The yield of acrylic esters was about 40 and 66percent with n-hexyl and β-phenethyl alcohol, respectively.
Substituent Effects on the Intramolecular Photochemical Reactions of Phenyl-Ethenyl Non-conjugated Bichromophoric Systems
Ellis-Davies, Graham C. R.,Gilbert, Andrew,Heath, Peter,Lane, Jon C.,Warrington, John V.,Westover, David L.
, p. 1833 - 1842 (2007/10/02)
The effects of substitution on the photochemistry of phenyl-ethenyl bichromophoric systems are reported.Methyl substitution at the 2-, 3-, 5-, and 1,1,2-positions in the pentene moiety of 5-phenylpent-1-ene reduces both reaction efficiency and selectivity but in contrast to intramolecular analogues the photoreaction of 3-phenethylcyclohexene is comparable with that of the corresponding cyclopentene.Incorporation of ester units in the connecting unit between the chromophores or on the ethene inhibits intramolecular cyclisation as does the presence of para OMe, CN, or COMe groups in 5-phenylpent-1-ene.In contrast reaction selectivity and efficiency are greatly promoted by ortho Me or OMe groups and the products reflect exlusive 1,3-cycloaddition.The presence of a para Me group in 5-phenylpent-1-ene leads to specific 2,6-intramolecular cyclisation but the reaction of the meta-Me derivative leads to four products derived from 1,3- and 1,5-intramolecular cycloaddition.The observations are discussed in terms of mechanisms of arene-ethene photoreactions and preferred conformations of the bichromophores.
