Trimethyl-1,4-Benzoquinone Synthesis via 2,3,6-Trimethylphenol Catalytic Oxidation by Oxygen in the Presence of Non-Keggin-Type Mo-V-Phosphoric Heteropoly Acid Solutions

In the present study, the modified （non-Keggin-type） aqueous solutions of Mo-V-phosphoric heteropoly acids HaPzMoyVx,Oh （HPA-x＇） were applied as homogeneous catalysts for the two-stage oxidation of TMP （2,3,6-trimethylphenol） by oxygen into TMQ （2,3,5-trimethyl-l,4-benzoquinone）, the latter being the key intermediate in the synthesis of vitamin E. The TMQ yield was analyzed regarding solvent type, reaction temperature, molar HPA-x ＇：TMP ratio, and the concentration of vanadium （V） in the HPA-x＇ solution. The TMQ yield was found to depend strongly on the catalyst redox potential and the rate of electron transfer. The results obtained enabled to establish the optimal reaction conditions as well as to suggest the reaction mechanism. In the target reaction, which proceeds in the two-phase system, the TMQ yield is higher than 99%. After phase separation, the catalyst is rapidly regenerated by oxygen and reused.

Tetrachloro-1,4-benzoquinone induces apoptosis of mouse embryonic stem cells

Pentachlorophenol（PCP） is a widespread,persistent environmental contaminant,and it is enzymatically activated to form a reactive metabolite,tetrachloro-l,4-benzoquinone（TCBQ）.To our knowledge,there is no information about TCBQ toxicity on embryonic stem cells.Here,we demonstrated that TCBQ induced significantly apoptosis of mouse embryonic stem cells in a concentration-dependent manner.We also showed that TCBQ elevated genomic5-hydroxymethylcytosine（5hmC） by affecting ten-eleven translocation（Tet） dioxygenases in mouse embryonic stem cells.We further investigated whether Tet dioxygenases were implicated in TCBQ-induced apoptosis.By depleting all three dioxygenases（Tet1-3）,we found that Tet dioxygenases slightly inhibited both early and late apoptosis induced by TCBQ at a low concentration（30 μmol/L）.Meanwhile,treated by TCBQ at higher concentrations（40and 50 μmol/L）,the total percentage of apoptotic cells was not affected by Tet dioxygenases.However,Tet dioxygenases tended to arrest mouse ES cells to be at early apoptotic stage and to reduce the cells to enter later apoptotic stage.These results indicate that Tet dioxygenases play a role in shaping TCBQ-induced apoptosis in mouse embryonic stem cells.Our study provides new insights into the toxicology of PCP and its reactive metabolite TCBQ.

Elevated 5-hydroxymethycytosine and cell apoptosis induced by tetrachloro-1,4-benzoquinone in mouse embryonic stem cells

Pentachlorophenol（PCP）has been extensively used as a fungicide,bactericide,herbicide,molluscicide.algaecide and insecticide worldwide（Ahlborg and Thunberg,1980：Choudhury et al.,1986）.Although PCP is primarily used as a preservative for wood and wood products,it has been also used in a variety of other products,including adhesives,construction materials,leather and paper.

Synthesis of substituted 1,2-benzoquinones and substituted 3-hydroxy-4 (1H) -pyridinones: Application of oxidation-Michael addition in organic synthesis

Catechol (1) and 2-ethoxy-2-ethyl-3-hydroxy-4(1H)-pyridinone (4) derivatives can be oxidized to give ortho-quinone of 1,2-benzoquinone (2) and 2-ethoxy-2-ethyl-1,2(2H)-pyridine 3,4-dione (5) that subsequently dew Michael addition with nucleophiles. This reaction served a convenient route to synthesize 4,5-disubstituted 1,2-benzoquinones (3a-c) and 6-substituted-3-hydroxy-4(1H)-pyridinones (6a-f).

Heterocyclization of thiocarbonohydrazides:Facile synthesis of 5-unsubstituted-1,3,4-thiadiazoles

2-（Hydrazinecarbothioyl）-N-substituted hydrazinecarbothioamides react with 2,3,5,6-tetrachloro-1,4-benzoquinone in high yields in a novel fast and facile method to give 5-unsubstituted-1,3,4-thiadiazole-2-amine derivatives.The synthesized compounds were characterized by spectroscopic methods and confirmed by using X-ray crystallography.A rationale for the formation of the products is presented.