- NaBH4-TMEDA and a palladium catalyst as efficient regio- and chemoselective system for the hydrodehalogenation of halogenated heterocycles
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The pair NaBH4-TMEDA as hydride source and a palladium catalyst in THF prove to be an efficient system for the hydrodehalogenation of halogenated heterocycles with one or more heteroatoms. In general, Pd(OAc) 2-PPh3 rapidly hydrodehalogenates reactive halo-heterocycles such as bromo-pyridines, -quinolines, -thiophenes, -indoles, -imidazoles, etc., at room temperature in very good yields, whereas in most cases PdCl2(dppf) reduces less reactive halides such as chloro-pyridines, -quinolines, -pyrimidines and bromo-indoles, -benzofurans, etc. Moreover, PdCl2(tbpf) shows to be even more active removing the 2- and 5-chlorine from both thiophene and thiazole rings. The reaction conditions tolerate various functional groups, allowing highly chemoselective reactions in the presence of halide, ester, alkyne, alkene and nitrile substituents. Moreover, with a proper selection of the catalyst it is also possible to obtain a good control in the regioselective hydrodehalogenation of a variety of polyhalogenated substrates.
- Chelucci, Giorgio,Figus, Susanna
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p. 191 - 209
(2014/07/21)
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- Regioselective C-C bond formation reactions on 2,3-dibromo- and 2,3,5-tribromobenzofuran as an access to multiply substituted benzofurans. Total syntheses of eupomatenoids 3, 4, 5, 6, and 15
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Regioselective C-C-bond formation reactions at 2,3-dibromobenzofuran (1) and 2,3,5-tribromobenzofuran (6) were studied. Pd-catalyzed Sonogashira and Negishi cross-coupling occurred with perfect regioselectivity at carbon atom C-2 to provide 2-substituted 3-bromobenzofurans (12, 14) and 3,5-dibromobenzofurans (17, 18) in 50-91% yield. A regioselective displacement of the bromine substituents in 3,5-dibromobenzofurans 18 was achieved by a halogen-metal exchange reaction at carbon atom C-3 and by a Nicatalyzed Kumada cross-coupling at C-5. The methodology was applied to the synthesis of eupomatenoids 3, 4, 5, 6, and 15 (5). The synthesis of these compounds was achieved in overall yields of up to 60%.
- Bach, Thorsten,Bartels, Marc
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p. 925 - 939
(2007/10/03)
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- Benzofuranyl 3,5-bis-polyamine derivatives as time-dependent inhibitors of trypanothione reductase
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The synthesis and evaluation of 3,5-disubstituted benzofuran derivatives as time-dependent inhibitors of the protozoan oxidoreductase trypanothione reductase are reported. These molecules were designed as simplified mimetics of the naturally occurring spermidine-bridged macrocyclic alkaloid lunarine 1, a known time-dependent inhibitor of trypanothione reductase. In this series of compounds the bis-polyaminoacrylamide derivatives 2-4 were all shown to be competitive inhibitors, but only the bis-4-methyl-piperazin-1-yl-propylacrylamide derivative 4 displayed time-dependent activity. The kinetics of time dependent inactivation of trypanothione reductase by 1 and 4 have been determined and are compared and discussed herein.
- Hamilton, Chris J.,Saravanamuthu, Ahilan,Fairlamb, Alan H.,Eggleston, Ian M.
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p. 3683 - 3693
(2007/10/03)
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