PEG-stabilized cobalt nanoparticles were prepared by thermal decomoposition of [Co2(CO)8] in PEG and were shown to be highlyactive and selectivecatalysts, for intra- and intermolecular Pauson-Khand reactions (PKR), in organic solvents or aqueous media.
Raney Cobalt: An Effective and Recyclable Catalyst for the Pauson–Khand Reaction
作者:Jean-Luc Muller、Annika Rickers、Walter Leitner
DOI:10.1002/adsc.200600453
日期:2007.2.5
Commercially available Raneycobalt is broadly applicable as a catalyst in intra- and intermolecular Pauson–Khand reactions (PKR). The activity of Raneycobalt compares favourably with that of previously described heterogeneous or heterogenised cobalt systems. The major reaction pathway appears to occur at the solid catalyst which can be efficiently separated and reused by filtration and/or exploiting
Alkyne-dicobalthexacarbonyl complexes are readily prepared by the reduction of cobalt bromide by Zn in the presence of alkynes in THF while bubbling carbon monoxide under ambient conditions. The complexes prepared in this way react with olefins to give the corresponding Pauson-Khand cyclopentenones in moderate to good yields. The alkyne-dicobalthexacarbonyl complexes can be also prepared in situ by