Catalytic stereoselective addition to alkynes. Borylation or silylation promoted by magnesia-supported iron oxide and cis-diboronation or silaboration by supported platinum nanoparticles

摘要: Abstract Iron oxide nanoparticles supported on magnesia (FeO/MgO) have been prepared by NaBH4 reduction of Fe(SO4) MgO and spontaneous reoxidation upon storage. XPS FeO/MgO indicates the presence Fe(0) (16%) Fe(II) (84%) this solid. TEM images show that catalytically active is constituted iron about 25 nm dispersed fibrous MgO. in catalytic amounts triphenylphosphine promotes highly regio- stereoselective monoborylation aromatic, aliphatic, terminal internal alkynes. Chemical analysis liquid after reaction control experiments using salts absence or PPh3 supports catalysis heterogeneous. The possibility trace copper impurities present precursor influence activity was studied a commercially available high-purity as (99.999% Fe purity) showing again good (but lower) activity. In addition, experiment catalyst containing 30 times higher Cu than low purity did not lead to complete alkyne conversion, although product formation observed large extent. Alkynes react with chemoselectivity versus alkenes. contrast FeO/MgO, Pt carbon efficiently diboronation silaboration alkynes at lower temperature render cis configured diboronated silaborated alkene.