14538-50-2Relevant academic research and scientific papers
Substituents Have a Large Effect on Photochemical Generation of Benzyl Cations and DNA Cross-Linking
Fan, Heli,Sun, Huabing,Peng, Xiaohua
, p. 7671 - 7682 (2018)
Photoactivated DNA interstrand cross-linking agents have a wide range of biological applications. Recently, several aryl boronates have been reported to induce DNA interstrand cross-link (ICL) formation via carbocations upon photoirradiation. Herein, we synthesized a series of new bifunctional phenyl compounds to test the generality of such a mechanism, and to understand how the chemical structure influences carbocation formation and the DNA cross-linking process. These compounds efficiently form DNA ICLs via generated benzyl cations upon 350 nm irradiation. The DNA cross-linking efficiency and the pathway for carbocation generation depend on both the aromatic substituents and the leaving groups. Bromine as a leaving group facilitates the DNA cross-linking process in comparison with trimethyl ammonium salt. Both electron-donating and -withdrawing substituents induce bathochromic shifts, which favor photoinduced DNA ICL formation. For the bromides, the benzyl cation intermediates were generated through oxidation of the corresponding benzyl radicals. However, for the ammonia salts, the benzyl cations were formed through two pathways: either through oxidation of the benzyl radicals or by direct heterolysis of the C?N bond. Photoinduced C?N homolysis to form benzyl radicals occurred with compounds having donating substituents, whereas direct heterolysis of the C?N bond occurred with those bearing withdrawing substituents. The adducts formed between 1 a and four natural nucleosides were characterized, indicating that the alkylation sites for the photogenerated benzyl cations are dG, dA, and dC.
Pd-Catalyzed ipso, meta-Dimethylation of ortho-Substituted Iodoarenes via a Base-Controlled C-H Activation Cascade with Dimethyl Carbonate as the Methyl Source
Wu, Zhuo,Wei, Feng,Wan, Bin,Zhang, Yanghui
supporting information, p. 4524 - 4530 (2021/05/04)
A methyl group can have a profound impact on the pharmacological properties of organic molecules. Hence, developing methylation methods and methylating reagents is essential in medicinal chemistry. We report a palladium-catalyzed dimethylation reaction of ortho-substituted iodoarenes using dimethyl carbonate as a methyl source. In the presence of K2CO3 as a base, iodoarenes are dimethylated at the ipso- and meta-positions of the iodo group, which represents a novel strategy for meta-C-H methylation. With KOAc as the base, subsequent oxidative C(sp3)-H/C(sp3)-H coupling occurs; in this case, the overall transformation achieves triple C-H activation to form three new C-C bonds. These reactions allow expedient access to 2,6-dimethylated phenols, 2,3-dihydrobenzofurans, and indanes, which are ubiquitous structural motifs and essential synthetic intermediates of biologically and pharmacologically active compounds.
Synthesis of functionalized alkyl substituted benzoquinones by Rh-catalyzed additions of boronic acids
Veguillas, Marcos,Rojas-Martín, Jaime,Ribagorda, María,Carre?o, M. Carmen
supporting information, p. 5386 - 5394 (2017/07/10)
A general synthetic route to γ-oxo alkyl or α-hydroxy benzyl 2-substituted benzoquinones has been developed through a one-pot Rh-catalyzed C-C bond formation/oxidative demethylation sequence from 2,5-dimethoxy aryl boronic acids and several electron deficient alkenes or aldehydes. The process allows rapid access to functionalized benzoquinones under very mild conditions and good yields. We disclose the first example of a Rh-catalyzed 1,4-addition reaction of benzoquinonyl boronic acid to methyl vinyl ketone and other conjugate acceptors, which allows the direct synthesis of 2-(γ-functionalized alkyl) substituted benzoquinones.
C-D-glucopyranosyl derivatives of tocopherols - Synthesis and evaluation as amphiphilic antioxidants
He, Li,Galland, Stephanie,Dufour, Claire,Chen, Guo-Rong,Dangles, Olivier,Fenet, Bernard,Praly, Jean-Pierre
experimental part, p. 1869 - 1883 (2009/04/04)
Treatment of dimethylhydroquinone dimethyl ethers (ortho and meta isomers) with glycopyranose pentaacetates (D-gluco, D-galacto) in the presence of SnCl4 and F3CCO2Ag selectively afforded the corresponding C-β-D-glycosyl derivatives by aromatic electrophilic substitution. Oxidation of the dimethoxybenzene moiety with ceric ammonium nitrate delivered C-β-D-glycosyl-dimethylbenzoquinones, which were reduced with Na2S2O4 to the corresponding C-β-D-glycosyldimethylhydroquinones. ZnCl2-catalyzed cyclization either with methylbut-2-en-1-ol (prenyl alcohol) or with all-racemic phytol led to acetyl-protected C-β-D-glycosyl chromanols or C-β-D-glycosyl tocopherols, the sugar residues of which were deacetylated under base catalysis conditions. These new molecules were evaluated as antioxidants in terms of their ability to inhibit the peroxidation of linoleic acid in SDS micelles. The position of the C-glucosyl moiety on the phenolic nucleus emerges as the critical structural determinant of their activity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
A convenient route for the synthesis of plumbagin
Mohan, H. Rama,Rao, A. S.
, p. 1044 - 1046 (2007/10/03)
An efficient synthesis of plumbagin 1 has been carried out starting from 2, 6-dimethylbenzoquinone 4. Two of the key steps are: (1) prepared of aldehyde 2 and (ii) aromatization of 3 via conversion to enol acetate 7 followed by DDQ dehydrogenation to afford 8.
Selective nitration versus oxidative dealkylation of hydroquinone ethers with nitrogen dioxide
Rathore,Bosch,Kochi
, p. 6727 - 6758 (2007/10/02)
Various alkyl-substituted p-dialkoxybenzenes (ArH) react readily with nitrogen dioxide (NO2) in dichloromethane solution via either nitration (ArNO2) or oxidative dealkylation to quinones (Q). Spectral transients indicate that these coupled processes proceed from the dialkoxybenzene radical cation (ArH+) formed as the common reactive intermediate from electron-transfer in the disproportionated precursor [ArH, NO+]NO3-. In fast subsequent steps, ArH+ undergoes homolytic coupling with NO2 (which leads to aromatic nitration) and nucleophilic attack of NO3- (which results in oxidative dealkylation). As such, the competition between nitration and oxidative dealkylation is effectively modulated by solvent polarity and added nitrate.
The Structure and Synthesis of Some Minor Xanthones from the Lichen Rinodina thiomela
Elix, John A.,Gaul, Kim L.,Jiang, Hui
, p. 95 - 110 (2007/10/02)
The total synthesis of the xanthones 5,7-dichloro-8-hydroxy-2-methoxy-1,3-dimethyl-9H-xanthen-9-one (10), 5,7-dichloro-2,8-dihydroxy-1,3-dimethyl-9H-xanthen-9-one (11), 2-dechloro-8-O-methylthiomelin (6), 2-dechlorothiomelin (8), 4-dechloro-8-O-methylthio
Redox-active crown ethers. Electrochemical and electron paramagnetic resonance studies on alkali metal complexes of quinone crown ethers
Delgado, Milagros,Wolf Jr., Robert E.,Hartman, Judithann R.,McCafferty, Gillian,Yagbasan, Rahmi,Rawle, Simon C.,Watkin, David J.,Cooper, Stephen R.
, p. 8983 - 8991 (2007/10/02)
Structural studies on [M(NCS)·(5QC-HQDME)] (M = Li, Na) as well as free 6QC-HQDME and [M(NCS)· (6QC-HQDME)] (M = Na, K) (where 5QC-HQDME is 15,17-dimethyl-16,18-dimethoxy-3,6,9,12-tetraoxabicyclo-[12.3.1]octadeca(1,14, 16)triene, and 6QC-HQDME is 15,17-dimethyl-16,18-dimethoxy-3,6,9,12,15-pentaoxabicyclo-[15.3.1]heneico(1,14, 16)triene) show that in all cases the metal ion binds to the anisole oxygen atom in the 1-position. Only in the case of [K(NCS)·(6QC-HQDME)] do both benzylic O atoms bind to the metal ion; in the other complexes only one of these O atoms interacts with M+. In each complex all of the non-benzylic crown O atoms coordinate. These results indicate that the benzylic O atoms contribute suboptimally to complexation. Crystallographic data are as follows: [Li(NCS)· (5QC-HQDME)], monoclinic, C19H28NO6SLi, space group P2}/n, a = 14.103 (4) A?, b = 8.493 (4) A?, c = 19.128 (8) A?, β = 108 70 (9)°, Z = 4; [Na(NCS)·(5QC-HQDME)], monoclinic, C19H28NO6SNa, space group P21/c, a = 10.182 (4) A?, b = 8.601 (1) A?, c = 25.631 (3) A?, β= 97.29 (3)°, Z = 4; 6QC-HQDME, orthohombic, C20H32O7, space group P212121, a = 8 195 (1) A?, b = 11.541 (1) A?, c = 22.449 (3) A?, Z = 4; [Na(NCS)·(6QC-HQDME)]·MeCN, monoclinic, C23H35N2O7SNa, space group P21/c, a = 11.308 (1) A?, b = 14.521 (2) A?, c = 16.440 (4) A?, β= 91.56 (1)°, Z = 4; [K(NCS)·(6QC-HQDME)], monoclinic, C21H32NO7SK, space group P21/c, a = 17.377 (3) A?, b = 10.600 (2) A?, c = 27.538 (7) A?, β= 102.41 (3)°, Z = 8. Electrochemical and EPR studies show that redox-active crown ethers incorporating quinone groups successfully couple ion binding by the crown ether to the redox state of the quinone group. Alkali metal ions cause potential shifts that establish-differential redox-induced complexation that qualitatively and quantitatively differs from ion-pairing effects. They also perturb the EPR hyperfine splittings in the semiquinone moieties in a characteristic fashion, as well as in one case giving rise to 23Na superhyperfine splitting.
Synthesis of 1,4-Benzoquinone Derivatives Having Two Side-Armed Polyethers and Crown Ethers, and Their Electrochemical Study in the Presence of Alkali Metal Cations (Na+ and K+)
Togo, Hideo,Hashimoto, Kiichi,Morihashi, Kenji,Kikuchi, Osamu
, p. 3026 - 3028 (2007/10/02)
Several crown ethers and two side-armed polyethers which have reducible quinonoid groups were prepared.Some of them, 7a, 7b, and 7d, showed highly enhanced cation-binding properties for the Na+ cation upon electrochemical reduction.
