The reaction of a copper complex bearing iminosemiquinone ligands with a CF3(+) source provides an unprecedented Cu(II)-CF3 complex through ligand-based oxidation. Reactivity of this complex leads to ...nucleophilic trifluoromethylation of the ligand, suggesting an electronic interplay that results in a formal umpolung of the initial CF3(+).
Total Synthesis of Norbadione A Bourdreux, Yann; Nowaczyk, Stéphanie; Billaud, Célia ...
Journal of organic chemistry,
01/2008, Letnik:
73, Številka:
1
Journal Article
Recenzirano
A short, convergent synthesis of the mushroom pigment norbadione A is described. The construction of an appropriately substituted naphtholactone intermediate involved a regioselective Diels−Alder ...reaction between a bis(triisopropylsilyloxy)diene and 2,6-dichlorobenzo-1,4-quinone. A double Suzuki−Miyaura cross-coupling between a diboronate and two identical enol triflates was another key feature of the synthesis.
A recently reported high-throughput screening strategy has been applied to the rapid selection of new water-soluble antioxidants that display strong protective activities. Based on a competitive ...immunoassay, a triple-screening procedure was used to evaluate the ability of different compounds to protect thymidine under different oxidative stresses. The pro-oxidant effect of norbadione A in the presence of iron was observed, while some pulvinic acid derivatives proved strongly protective during γ radiolysis, UV irradiation, and Fenton-like oxidation.
We present a new high-throughput screening method for the selection of powerful water-soluble antiradiation compounds. This method, which uses conventional immunoassay techniques, allowed the ...capacity of a given compound to protect thymidine from irradiation to be evaluated. By applying this assay to an antioxidant library, we showed for the first time that norbadione A, a well-known mushroom pigment, has pronounced atypical antiradiation properties.
A well-defined copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF
3
+
source into CF
&z.rad;
3
radicals. This redox behavior is enabled by the ...ligand which shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(
ii
). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF
&z.rad;
3
radicals.
Cooperative catalysis involving copper(
ii
) complex bearing redox ligands allows generation of CF
&z.rad;
3
radicals through ligand-based SET while metallic oxidation state is preserved.
Amino-substituted biphenyls were obtained by Suzuki cross-coupling of 2,6-dibromoaniline with a phenylboronic acid (substituted with Me, NO(2), OH, OMe or Cl) preferably assisted by microwave ...irradiation. Conversion of the amino group into a thiol preceded a base-induced intramolecular substitution, also facilitated by microwave heating, to generate the second C-S bond of the target dibenzothiophene. The 1-, 2-, 3- or 4-substituted 6-halodibenzothiophenes obtained were subjected to a palladium-mediated coupling with 2-morpholin-4-yl-8-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-4H-chromen-4-one to give the respective 6-, 7-, 8- or 9-substituted dibenzothiophen-4-ylchromenones. These compounds were evaluated as inhibitors of DNA-dependent protein kinase (DNA-PK) and compared to the parent 8-(dibenzob,dthiophen-4-yl)-2-morpholin-4-yl-4H-chromen-4-one. Notably, derivatives bearing hydroxy or methoxy substituents at C-8 or C-9 retained activity, whereas substitution at C-7 lowered activity. Substitution with chloro at C-6 was not detrimental to activity, but a chloro group at C-7 or C-8 reduced potency. The data indicate permissive elaboration of hydroxyl at C-8 or C-9, enabling the possibility of improved pharmaceutical properties, whilst retaining potency against DNA-PK.
A well-defined copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF sub(3) super(+) source into CF super(&z.rad; ) sub(3) radicals. This redox ...behavior is enabled by the ligand which shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(ii). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF super(&z.rad; ) sub(3) radicals.
A well-defined copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF
source into CF˙3 radicals. This redox behavior is enabled by the ligand which ...shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(ii). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF˙3 radicals.
Cooperative catalysis involving copper(
ii
) complex bearing redox ligands allows generation of CF˙3 radicals through ligand-based SET while metallic oxidation state is preserved.
A well-defined ...copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF
3
+
source into CF˙3 radicals. This redox behavior is enabled by the ligand which shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(
ii
). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF˙3 radicals.
A versatile new method for the preparation of NHC boranes starting from two stable, readily available reactants―an heterocyclic salt and an amine or phosphine−borane―is reported. It uses a Lewis base ...exchange at boron and provides easy access to new NHC boranes, in particular B-substituted borane ones.
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