5-溴-6-甲氧基-2-丙酰基萘的钯催化氢化脱溴

溴甲氧基丙酰基萘;5-溴-6-甲氧基-2-丙酰基萘的钯催化氢化脱溴     

Hydrodehalogenation of 4-chlorophenol and 4-bromophenol over Pd–Fe/Al2O3: influence of catalyst reduction conditions

The reduction of monometallic Pd/Al₂O₃ and bimetallic PdFe/Al₂O₃ catalysts produced by co-impregnation or sequential impregnation of the support with metal salts was possible not only under high temperature hydrogen treatment but also at 30 °C under the action of aqueous phenol solution and hydrogen. According to the XPS data, both reduction routes provided sufficient degrees of Pd reduction required for fast hydrodehalogenation of 4-chlorophenol and 4-bromophenol to phenol in aqueous solutions. The degree of Pd reduction was higher in the co-impregnated bimetallic PdFe catalyst, which was more efficient in transformation of 4-bromophenol; the bimetallic catalysts were more stable than the monometallic Pd one in the conversion of 4-chlorophenol.     

Synthesis of meso-Free Decaphyrin(1.1.1.1.1.1.1.1.1.1) by a Hydrodebromination Protocol; Aromaticity and Solvent-Polarity Dependent Conformational Change

A meso-free β-bromodecaphyrin has been constructed by [2+3+2+3] type acid-catalyzed cross-condensation and subsequent oxidation. Hydrodebromination of this tetrabromodecaphyrin with NaBH₄ in the presence of TMEDA and palladium catalyst afforded β-unsubstituted doubly meso-free [46]decaphyrin(1.1.1.1.1.1.1.1.1.1) as the first example of β-unsubstituted meso-free regular expanded porphyrins with the number of pyrrole units larger than eight. It exhibits distinct aromaticity originating from its 46π-conjugated electronic circuit and flexible conformational change between non-twisted and doubly twisted forms depending on the solvent-polarity. Their distinct conformations have been analyzed by combined experimental and theoretical investigations.     

Hydrodebromination of bromoarenes using Grignard reagents catalyzed by metal ions

The metal salts, FeCl^·₂4H₂O, FeCl₃, NiCl₂, CoCl₂, CuBr and some iron complexes were found to be efficient catalysts for hydrodebromination of bromoarenes under mild reaction conditions with two equivalents of Grignard reagents. Among them, the iron systems showed the best behavior regarding economic and environmental considerations. All the alkyl Grignard reagents (except CH₃MgCl) and p‐tolylMgBr were promising reductive reagents with the formation of their homo‐coupling products. Copyright © 2008 John Wiley & Sons, Ltd.