A selective and high yielding synthesis of polysubstituted pyrazoles through a VLPC (visible light photoredox catalysis)-promoted reaction of hydrazine with Michael acceptors is reported. The method employs very mild reaction conditions and uses air as the terminal oxidant, which makes the process environmentally benign. Different types of Michael acceptors with various substituents can undergo the reaction to afford corresponding pyrazoles in good to excellent yields. The reaction is proposed to go through VLPC-promoted oxidation of hydrazine to diazene followed by its addition to Michael acceptors, other than the conventional condensation of hydrazine with a carbonyl.
A metal-free protocol through visible light mediated oxidative cleavage of CC bonds to directly construct CN bonds has been developed for the conversion of alkenes to hydrazones under mild conditions.
Over the past few decades, ylide chemistry has been significantly extended to an area beyond olefination and small ring formation, among which ylide [4 + 1] annulation has been extensively explored, and five-membered ring structures, such as dihydrofurans, isoxazolines, pyrrolines, indoles, dihydropyrazoles and cyclopentenones, can be readily constructed through this type of transformation. An overview of the recent advances in this field is presented herein. Ylide [4 + 1] annulations are reviewed by highlighting their product diversity, selectivity and applicability, and the mechanistic rationale is presented when possible.
1-Ethyl-3-methylimidazolium chlorine
([Emim]Cl) and 1-ethyl-3-methylimidazolium
bromide ([Emim]Br) as an additive to working fluid [lithium bromide
aqueous solution (H2O/LiBr) and lithium chloride aqueous
solution (H2O/LiCl)] of absorption cycles were proposed.
The vapor pressure of H2O + LiCl + [Emim]Cl (mass ratio
LiCl/[Emim]Cl = 2) in the temperature from 314.79 to 435.48 K, H2O + LiCl + [Emim]Br (mass ratio LiCl/[Emim]Br = 2) in the
temperature from 317.62 to 431.27 K, and H2O + LiBr + [Emim]Cl
(mass ratio LiBr/[Emim]Cl = 2) in the temperature from 303.10 to 409.91
K was measured by the boiling point method. The mass fractions of
the absorbent were from 0.30 to 0.60. The experimental data were regressed
using the Antoine-type equation, and the average absolute relative
deviation (AARD %) between the experimental data and calculated values
of three systems was 0.44, 0.51, and 0.54%. Compared with that of
the previously reported ionic liquids, ([Emim]Ac) as an absorbent
for LiBr + H2O, vapor pressure of these four systems follows
the order LiCl + [Emim]Cl + H2O < LiCl + [Emim]Br +
H2O < LiBr + [Emim]Cl + H2O < LiBr + [Emim]Ac
+ H2O. The proposed ternary systems have better water affinity
and can be promising alternative working fluids in the absorption
cooling system.
Cellular senescence is a state of irreversible cell growth arrest. Increasing evidence suggests that cellular senescence contribute to tumour suppression in vivo. However, only a few anti-cancer drugs have been discovered to induce cellular senescence. Searching for new compounds which can inhibit cancer cell growth by inducing senescence is becoming one of the most attractive research fields. To test the effects of candidate compounds on cancer cell growth, cell proliferation assays, senescence-associated β-galactosidase (SA-β-gal) staining, and flow cytometry assay were performed. Immunofluorescence, western blot, and qRT-PCR experiments were used to further study the molecular mechanisms of the candidate compounds. We demonstrated that a pyridine derivative, 4-(4-fluorophenyl)-2-phenyl-5, 6, 7, 8-tetrahydroquinoline (FPTHQ), from a pool of 46 compounds can induce senescence of ovarian cancer cells in a dose-dependent manner. FPTHQ caused growth inhibition by inducing G0/G1 cell cycle arrest in A2780 cells. Increased activities of SA-β-gal were observed in FPTHQ-treated A2780, OVCAR-3 and SKOV-3 cell lines. In addition, FPTHQ treatment increased the protein levels of MMP3 and the mRNA levels of IL-6 and IL-8 in A2780 cells, indicating the appearance of senescence-associated secretary phenotype (SASP) in the cells. Furthermore, we found that p21 was up-regulated and DNA damage was accumulated in FPTHQ-treated ovarian cancer cells. So far, our data suggest that FPTHQ can induce senescence in multiple ovarian cancer cell lines through activation of p21 signalling pathway by causing excessive DNA damage.
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