1835-02-5Relevant articles and documents
Effect of cyclodextrin complexation on the photochemistry of the lignin model α-guaiacoxyacetoveratrone
Okano,Ovans,Zunic,Moorthy,Bohne
, p. 1356 - 1365 (1999)
The photodecomposition of α-guaiacoxyacetoveratrone (GAV) in homogeneous solvents and in aqueous cyclodextrin solutions was studied by following the fluorescence emission of the photoproducts formed. The same qualitative behavior as previously observed for the photodegradation quantum yield measurements was reproduced in the fluorescence studies in dry or wet methanol and acetonitrile. The yield for GAV photodegradation in water is smaller than in the organic solvents. Complexation of GAV to β- and γ-cyclodextrins leads to an increase in the photodecomposition yield, especially during the early part of the photodecomposition kinetics. The transients formed in the photolysis of GAV in water are similar to those observed in acetonitrile, and the lifetime of triplet GAV in water is 130 ns. In addition, solvated electrons were formed when GAV was photolyzed in water. Complexation of GAV to cyclodextrins leads to an increase in the triplet yield compared to the radical yield and a mode rate shortening of the triplet lifetime.
Synthesis and Fluorescence Properties of Novel indol-3yl-thiazolo[3,2-a][1,3,5]triazines and indole-3-carbaldehyde Schiff Bases
Sravanthi,Manju
, p. 1727 - 1738 (2015)
Novel photoactive 4-(4-chlorophenyl)-2-(1H-indol-3-yl)-6-substituted phenyl-2H-thiazolo[3,2-a][1,3,5]triazines were synthesized by the conjugate addition of ammonia to the indole-3-carbaldehyde Schiff bases followed by the condensation with 4-chlorobenzaldehyde. All the synthesized compounds were characterized by FT-IR, NMR, mass spectra and elemental analyses. Their antioxidant property, electrochemical and photophysical properties in different organic solvents were investigated. Comparative discussion on the photophysical properties of indole-3-carbaldehyde Schiff bases and 4-(4-chlorophenyl)-2-(1H-indol-3-yl)-6-substituted phenyl-2H-thiazolo[3,2-a][1,3,5]triazines has been described. The fluorescence quantum yield of Schiff bases (Φf = 0.66-0.70 in DMSO) found to be interestingly higher. High fluorescence quantum yield, large molar extinction coefficient, high stokes shift and smaller optical band gap positioning these new derivatives as an efficient metal free organic fluorescent and semiconductor material.
Design, synthesis and biological evaluation of 2-(3,4-dimethoxyphenyl)-6 (1,2,3,6-tetrahydropyridin-4-yl)imidazo[1,2-a]pyridine analogues as antiproliferative agents
Chitti, Surendar,Singireddi, SrinivasaRao,Santosh Kumar Reddy, Pochana,Trivedi, Prakruti,Bobde, Yamini,Kumar, Chandan,Rangan, Krishnan,Ghosh, Balaram,Sekhar, Kondapalli Venkata Gowri Chandra
, p. 2551 - 2558 (2019)
Two series of forty five novel 2-(3,4-dimethoxyphenyl)-6-(1,2,3,6-tetrahydropyridin-4-yl) imidazo[1,2-a]pyridine analogues (IPA 1–22, IPS 1–22 and IP-NH) have been designed, synthesized and structures confirmed by 1H NMR, 13C NMR, mass spectrometry. Furthermore, single crystal was developed for IPS-13. All the final derived conjugates were evaluated for their in vitro antiproliferative activity against a panel of diverse cancer cell lines viz., A549 (lung cancer), HeLa (cervical cancer), B16F10 (melanoma) and found to show potent anticancer activity on the tested cell lines. Many of them showed the IC50 values in the range 2.0–20.0 μM. The most active compounds (IPA 5,6,8,9,12,16,17,19 and IPS 7,8,9,22) from IPA and IPS series were screened to determine their cytotoxicity on HEK-293 (human embryonic kidney) normal cell line and were found to be nontoxic to normal human cells. The molecular interactions of the derivatised conjugates were also supported by molecular docking simulations. These derivatives may serve as lead structures for development of novel potential anticancer drug candidates.
Alkylation of monomeric, dimeric, and polymeric lignin models through carbon-hydrogen activation using Ru-catalyzed Murai reaction
Zuleta, Ernesto C.,Bozell, Joseph J.
, (2021/10/05)
In this study, we have assessed directed carbon-hydrogen activation (CHA) for alkylation of monomeric, dimeric, and polymeric lignin models using Murai's catalyst [RuH2(CO)(PPh3)3]. Based on related work from our laboratory showing that isolated organosolv lignin bears benzylic directing groups ideal for CHA reactions, this approach could offer new methodology for the valorization of biorefinery lignin. Monomeric and dimeric models bearing a keto group at the benzylic position undergo Ru-catalyzed alkylation in good to excellent yield. Similarly, models bearing a benzylic OH group also undergo alkylation via a tandem oxidation/alkylation process enabled by the Ru catalyst. Polymeric models show low levels of functionalization as a result of the poor solubility of the starting polymer. With unsymmetrical models, functionalization occurs first at the least sterically hindered ortho-site, but a subsequent alkylation, leading to disubstituted products can occur at the more sterically hindered site, leading to hexasubstituted arenes. The reaction shows sensitivity to free phenolic OH groups, which appears to reduce the yield in some reactions, and is also a contributing factor to the low yields observed with polymeric lignin models. Combining CHA methodology with lignin isolation technology able to introduce appropriate directing groups for catalytic functionalization will form the basis for improved conversion of lignin to high value chemical products.
An umpolung oxa-[2,3] sigmatropic rearrangement employing arynes for the synthesis of functionalized enol ethers
Gaykar, Rahul N.,George, Malini,Guin, Avishek,Bhattacharjee, Subrata,Biju, Akkattu T.
supporting information, p. 3447 - 3452 (2021/05/04)
An oxa-[2,3] sigmatropic rearrangement involving arynes is reported featuring the umpolung of ketones, where the C=O bond polarity is reversed. The in situ-generated sulfur ylides from β-keto thioethers and arynes undergo efficient rearrangement allowing the facile and robust synthesis of functionalized enol ethers in high yields and excellent functional group compatibility. Preliminary mechanistic studies rule out the possibility of Pummerer-type rearrangement operating in this case.