Laser Desorption electron impact mass spectrometry: Studies of ion radical fragmentation mechanisms and hydrogen/deuterium rearrangement in time-resolved experiments

Laser desorption of neutral molecules followed by electron impact ionization is shown to produce gaseous ion radicals that undergo fragmentation analogous to that observed with electron impact and field ionization. Spectra were measured of heptanal and four deuterium-labeled analogs regenerated from bisulfite derivatives, and compared with electron impact, chemical ionization and field ionization spectra published previously. Lifetimes of desorbed neutral molecules and of ions were found to influence the fragmentation process as reflected in isotope patterns. This is explained on the basis of internal energies.     

The activity of solutions of Ru3(CO)12 as catalysts for the fischer-tropsch reaction

Solutions of dodecacarbonyl-triangulo-triruthenium [Ru₃(CO)₁₂] have been shown to be catalyst precursors for the Fischer-Tropsch reaction; the catalyst formed under the reaction conditions is heterogeneous; no indication of homogeneous activity was found.     

Synthesis of new [1,2,3]triazoles and 1H-tetrazoles via reactions of 3,(5)-(Di)chloro-2H-1,4-(benz)oxazin-2-ones with diazocompounds or sodium azide

Treatment of 3,(5)-(di)chloro-2H-1,4-(benz)oxazin-2-ones with diazo compounds or sodium azide yields bi(tri)cyclic compounds which can be converted into [1,2,3]triazoles or 1,5-disubstituted tetrazoles via reactions with nucleophiles as methanol, water and amines.     

Homogeneous and heterogeneous asymmetric reactions: Part 11. Sonochemical enantioselective hydrogenation of trifluoromethyl ketones over platinum catalysts

Enantioselective sonochemical hydrogenation of alpha,alpha,alpha-trifluoromethyl ketones, namely, 1,1,1-trifluoroacetophenone and 1,1,1-trifluoro-phenylacetone was carried out over various platinum catalysts modified by cinchonidine in different solvents. Both compounds yielded the (R)-alcohol as major product. The reaction rates and the enantiomeric excesses were determined over Pt/C, Pt/SiO2, Pt/K-10 and Pt/Al2O3 catalysts under conventional conditions. Since Pt/Al2O3 exhibited the best catalytic performance the effect of ultrasound on the catalytic activity and enantioselectivity was tested using this catalyst applying different sonochemical pretreatments. These methods included a pretreatment before the reaction in hydrogen and oxygen or both. The ultrasonic irradiation was found to be highly advantageous in the case of trifluoroacetophenone, whereas only moderate changes were observed using trifluoro-phenylacetone. After insonation of the catalyst, the enantioselectivity was considerably improved. Both the aerobic and anaerobic sonochemical pretreatments resulted in significant improvement in optical yield (up to 49% and 17% ee, at room temperature under 10 bar in 1,2-dichlorobenzene). In parallel, the hydrogenation rates increased to a small extent (1.1-1.2-fold increase) after hydrogenative ultrasonic pretreatment, whereas the rates decreased by a factor of 1.5-2 after aerobic insonation. To obtain more insight into the process, the effect of insonation time on the activity and enantioselectivity and actual changes of the catalyst were also studied.     

Continuous enantioselective hydrogenation of activated ketones on a pt-cd chiral catalyst: use of h-cube reactor system

Summary The Pt-alumina-CD catalyzed enantioselective hydrogenations of ethylpyruvate (EP), ketopantolactone (KPL) and methyl benzoylformate (MBF) have been studied at first in an H-Cube flow hydrogenator in toluene and toluene + acetic acid. Based on the experience of previous studies carried out in batch-reactor and continuous flow systems, some parameters were kept constant (amount of catalyst, 380 mg; substrate concentration, 0.18 mol/L; temperature, 283 K), whereas others, namely chiral modifier (CD) concentration, hydrogen pressure and total liquid flow (TLF: substrate + modifier + solvent) were varied. In the course of enantioselective hydrogenation (R)-products were formed in excess: in the case of EP, KPL, MBF: 90, 60, 80 % enantioselectivities were obtained.     

Synthesis and structure of new arylnickel(II) malonato-complexes

Summary Interaction of malonate anions with chloro(aryl)bis(organophosphine)nickel(II) complexes leads to the formation of stable (aryl)(malonato)(organophosphine)nickel(II) species, as shown by i.r. and¹H n.m.r. data. The crystal and molecular structure of (diethylmalonato-O,O)(-naphthyl)(triphenylphosphine)nickel(II), determined by x-ray methods (space group P¯1,a=10.767(9),b=16.253(16),c=9.835(13)Å, =108.97(10)⁰, =106.08(10)⁰, =89.11(7)⁰,Z= 2;R= 0.070 for 3650 independent observed reflections), shows distorted square-planar O₂PC coordination about the nickel with bond distances: Ni-P, 2.142(2)Å; Ni-O, 1.888(5) and 1.936(5)Å; Ni-C, 1.887(8)Å. The parameters and bonding of the triphenylphosphine-nickel and naphthyl moieties in the complex are normal, whereas considerable electron-delocalisation occurs in the planar ethylmalonate moiety. The -naphthyl ligand is oriented almost perpendicularly to the NiO₂CP core-malonate plane.