ABSTRACT
A novel iron-catalyzed hydrogenation of nitroarenes to the corresponding amines is reported. An in situ combination of Fe(BF4)2·6H2O and phosphine allows for highly selective hydrogenation of a broad range of aromatic and nitroarenes tolerating different functional groups.
Subject(s)
Ferrous Compounds/chemistry , Phosphines/chemistry , Amines/chemistry , Catalysis , Hydrogenation , Nitrobenzenes/chemistryABSTRACT
Committed carbenes: The convenient application of bidentate carbene ligands is described for the hydrogenation of carboxylic acid esters. The ligand precursors are easily synthesized through the dimerization of N-substituted imidazoles with diiodomethane. The catalyst is generated in situ and exhibits good activity and functional group tolerance for the hydrogenation of aromatic and aliphatic carboxylic acid esters.
Subject(s)
Carboxylic Acids/chemistry , Methane/analogs & derivatives , Ruthenium/chemistry , Catalysis , Esters , Hydrogenation , Ligands , Methane/chemistryABSTRACT
A selective iron-based catalyst system for the hydrogenation of α,ß-unsaturated aldehydes to allylic alcohols is presented. Applying the defined iron-tetraphos complex [FeF(L)][BF4] (L = P(PhPPh2)3) in the presence of trifluoroacetic acid a broad range of aldehydes are reduced in high yields using low catalyst loadings (0.05-1â mol %). Excellent chemoselectivity for the reduction of aldehydes in the presence of other reducible moieties, for example, ketones, olefins, esters, etc. is achieved. Based on the in situ detected hydride species [FeH(H2)(L)](+) a catalytic cycle is proposed that is supported by computational calculations.
Subject(s)
Alcohols/chemical synthesis , Aldehydes/chemistry , Alkenes/chemistry , Iron/chemistry , Ketones/chemistry , Alcohols/chemistry , Catalysis , Combinatorial Chemistry Techniques , Hydrogenation , Molecular Structure , Phosphines/chemistry , Trifluoroacetic Acid/chemistryABSTRACT
Molecularly well-defined homogeneous catalysts are known for a wide variety of chemical transformations. The effect of small changes in molecular structure can be studied in detail and used to optimize many processes. However, many industrial processes require heterogeneous catalysts because of their stability, ease of separation and recyclability, but these are more difficult to control on a molecular level. Here, we describe the conversion of homogeneous cobalt complexes into heterogeneous cobalt oxide catalysts via immobilization and pyrolysis on activated carbon. The catalysts thus produced are useful for the industrially important reduction of nitroarenes to anilines. The ligand indirectly controls the selectivity and activity of the recyclable catalyst and catalyst optimization can be performed at the level of the solution-phase precursor before conversion into the active heterogeneous catalyst.
Subject(s)
Cobalt/chemistry , Nitro Compounds/chemistry , Oxides/chemistry , Aniline Compounds/chemistry , Catalysis , Kinetics , Oxidation-ReductionABSTRACT
Chemoselective cubes: Cubane-type [Mo(3)S(4)X(3)(dmpe)(3)](+) clusters (dmpe = 1,2-(bis)dimethylphosphinoethane), in combination with an azeotropic 5:2 mixture of HCOOH and NEt(3) as the reducing agent, act as selective cluster catalysts (X = H) or precatalysts (X = Cl) for the transfer hydrogenation of functionalized nitroarenes, without the formation of hazardous hydroxylamines.
Subject(s)
Aniline Compounds/chemical synthesis , Coordination Complexes/chemistry , Nitro Compounds/chemistry , Aniline Compounds/chemistry , Catalysis , Coordination Complexes/chemical synthesis , Hydrogenation , Molecular StructureABSTRACT
A novel iron-catalyzed transfer hydrogenation of alkynes to the corresponding alkenes applying formic acid as a hydrogen donor is reported. An in situ combination of Fe(BF(4))(2)·6H(2)O and tetraphos allows for highly selective hydrogenation of a broad range of aromatic and aliphatic alkynes tolerating different functional groups.
ABSTRACT
An easily accessible in situ catalyst composed of [{RuCl(2)(p-cymene)}(2)] and terpyridine has been developed for the selective transfer hydrogenation of aromatic nitro and azo compounds. The procedure is general and the selectivity of the catalyst has been demonstrated by applying a series of structurally diverse nitro and azo compounds (see scheme).
Subject(s)
Aniline Compounds/chemical synthesis , Azo Compounds/chemistry , Nitrobenzenes/chemistry , Ruthenium/chemistry , Aniline Compounds/chemistry , Catalysis , Cymenes , Hydrogenation , Molecular Structure , Monoterpenes/chemistry , Organometallic Compounds/chemistryABSTRACT
Pyrolysis of iron-phenanthroline complexes supported on carbon leads to highly selective catalysts for the reduction of structurally diverse nitroarenes to anilines in 90-99% yields. Excellent chemoselectivity for the nitro group reduction is demonstrated.
Subject(s)
Hydrocarbons, Aromatic/chemistry , Iron/chemistry , Nitro Compounds/chemistry , Amines/chemistry , Catalysis , Oxidation-Reduction , Substrate SpecificityABSTRACT
The first well-defined iron-based catalyst system for the reduction of nitroarenes to anilines has been developed applying formic acid as reducing agent. A broad range of substrates including other reducible functional groups were converted to the corresponding anilines in good to excellent yields at mild conditions. Notably, the process constitutes a rare example of base-free transfer hydrogenations.
