Solventless substitution chemistry of iron and ruthenium metal carbonyl complexes

ABSTRACT Solventless reactions of substituted cyclopentadienyl metal carbonyls of iron and ruthenium with electron donor ligands have been carried out. The reactions between CpFe(CO)2I and a range of phosphine ligands occurred in melt phase and yielded two typical compounds : salt product, [CpFe(CO)2PR3]I, and non-salt product, CpFe(CO)PR3I with the salt product being predominant. The complex [CpFe(CO)2]2 was used to catalyze these reactions. The progress of the reactions was followed by 1H NMR spectroscopy. The characterization of products correlates well with the products obtained when working in solution medium. The presence of a Me substituent on the Cp ring was found to favour the salt product formation but generally led to lower rates of reaction. Solventless reactions between RCpRu(CO)2I (R = H, Me) and solid phosphine ligands were also carried out. It has been observed that the ruthenium complexes were less reactive compared with their iron analogues but led to the same types of products namely salt and non-salt. The phosphite ligands were found to be less reactive than their phosphine analogues. In fact, the solventless reactions between RCpM(CO)2I (R = H, Me; M = Fe, Ru) were very slow even in the presence of [CpFe(CO)2]2 as a catalyst. However, when Me3NO.2H2O was added to the reaction mixture in solventless conditions, the non-salt product was obtained in a short period of time at 80oC. A range of cyclopentadienyl based metal complexes e.g [CpMo(CO)3]2, [MeCpRu(CO)2]2 etc. and palladium based compounds such as PdO, Pd/CaCO3 5% etc. were found to be good catalysts for the solventless reactions between CpFe(CO)2I and PPh3. Solventless migratory-insertion reactions have been successfully conducted between CpFe(CO)2CH3 and a range of solid phosphine ligands. Only the acetyl products, CpFe(CO)[PR3]COCH3 were obtained. SO2 insertion into RCpFe(CO)2R’ (R = H, CH3; R’ = CH3, CH2Ph) occurred quite easily at room temperature. However, when R was a carboxylic acid group, CO2H, no reaction took place. CO insertion into the same systems did not happen in solventless conditions

Fast microwave-assisted oxidation of 1,4-dihydropyridines with FeCl 3.SiO 2

Pyridine derivatives are easily obtained in high yields by microwave-promoted rapid oxidation of the corresponding 1,4-dihydropyridines with ferric chloride hexahydrate and silica gel under solvent-free conditions

Compositional Analysis of the High Molecular Weight Ethylene Oxide Propylene Oxide Copolymer by MALDI Mass Spectrometry

The composition of narrow distribution poly ethylene oxide-propylene oxide copolymer (Mw ~ 8700 Da) was studied using matrix assisted laser desorption ionization (MALDI) mass spectrometry. The ethylene oxide-propylene oxide copolymer produced oligomers separated by 14 Da. The average resolving power over the entire spectrum was 28,000. Approximately 448 isotopically resolved peaks representing about 56 oligomers are identified. Although agreement between experimental and calculated isotopic distributions was strong, the compositional assignment was difficult. This is due to the large number of possible isobaric components. The purpose of this research is to resolve and study the composition of high mass copolymer such as ethylene oxide-propylene oxide

Development of an optimized intumescent coating

Intumescent coatings for small diameter air launched missiles were studied. An aerodynamically smooth, moderately flexible coating, with excellent thermal efficiency was developed

The low temperature solvent-free aerobic oxidation of cyclohexene to cyclohexane diol over highly active Au/Graphite and Au/Graphene catalysts

The selectivity and activity of gold-catalysts supported on graphite and graphene have been compared in the oxidation of cyclohexene. These catalysts were prepared via impregnation and sol immobilisation methods, and tested using solventless and radical initiator-free reaction conditions. The selectivity of these catalysts has been directed towards cyclohexene epoxide using WO3 as a co-catalyst and further to cyclohexane diol by the addition of water, achieving a maximum selectivity of 17% to the diol. The sol immobilisation catalysts were more reproducible and far more active, however, selectivity towards the diol was lower than for the impregnation catalyst. The results suggest that formation of cyclohexane diol through solventless oxidation of cyclohexene is limited by a number of factors, such as the formation of an allylic hydroperoxyl species as well as the amount of in situ generated water

Aza-Michael mono-addition using acidic alumina under solventless conditions

Aza-Michael reactions between primary aliphatic and aromatic amines and various Michael acceptors have been performed under environmentally-friendly solventless conditions using acidic alumina as a heterogeneous catalyst to selectively obtain the corresponding mono-adducts in high yields. Ethyl acrylate was the main acceptor used, although others such as acrylonitrile, methyl acrylate and acrylamide were also utilized successfully. Bi-functional amines also gave the mono-adducts in good to excellent yields. Such compounds can serve as intermediates for the synthesis of anti-cancer and antibiotic drugs.peer-reviewe

An Efficient Synthesis of Pyridoxal Oxime Derivatives under Microwave Irradiation

Quaternary salts of pyridoxal oxime have been synthesized by the quaternization of pyridoxal oxime with substituted phenacyl bromides using microwave heating. Microwave-assisted rapid synthesis was done both in solvent (acetone) and under solvent-free conditions. Good to excellent yields (58%94%) were obtained in acetone in very short reaction times (35 min) as well as in the solvent-free procedure (42%78%) in very short reaction times (710 min) too. Effective metodologies for the preparation of pyridoxal oxime quaternary salts, having the advantagies of being eco-friendly, easy to handle, and performed in shorter reactions time are presented. The structure of compound 7, in which a 4-fluorophenacyl moiety is bonded to the pyridinium ring nitrogen atom, was unequivocally confirmed by the single-crystal X-ray diffraction method

Room temperature, solventless telomerization of isoprene with alcohols using (N-heterocyclic carbene)–palladium catalysts

The use of a custom-made palladium complex for the telomerisation of isoprene with alcohols under green conditions is described. Using a very low catalyst loading (0.1 mol%), this protocol allows for the reactions to be carried out without the need of high pressure equipment, at room temperature and under solventless conditions, affording high yields of telomerization products with high selectivity towards linear head-to-head and tail-to-head telomer

Expanding the palette of phenanthridinium cations

5,6-Disubstituted phenanthridinium cations have a range of redox, fluorescence and biological properties. Some properties rely on phenanthridiniums intercalating into DNA, but the use of these cations as exomarkers for the reactive oxygen species (ROS), superoxide, and as inhibitors of acetylcholine esterase (AChE) do not require intercalation. A versatile modular synthesis of 5,6-disubstituted phenanthridiniums that introduces diversity by Suzuki–Miyaura coupling, imine formation and microwave-assisted cyclisation is presented. Computational modelling at the density functional theory (DFT) level reveals that the novel displacement of the aryl halide by an acyclic N-alkylimine proceeds by an SNAr mechanism rather than electrocyclisation. It is found that the displacement of halide is concerted and there is no stable Meisenheimer intermediate, provided the calculations consistently use a polarisable solvent model and a diffuse basis set