Structural insights into aluminum chlorofluoride (ACF)

The structure of the very strong solid Lewis acid aluminum chlorofluoride (ACF, AlCl(x)F(3-x), x = 0.05-0.3) was studied by IR, ESR, Cl K XANES, (19)F MAS NMR, and (27)Al SATRAS NMR spectroscopic methods and compared with amorphous aluminum fluoride conventionally prepared by dehydration of alpha-AlF(3) x 3H(2)O. The thermal behavior of both compounds was investigated by DTA and XRD. In comparison to ACF, amorphous AlF(3) prepared in a conventional way is not catalytically active for the isomerization reaction of 1,2-dibromohexafluoropropane, which requires a very strong Lewis acid. Both compounds are mainly built up of corner-sharing AlF(6) octahedra forming a random network. The degree of disorder in ACF is higher than in amorphous AlF(3). Terminal fluorine atoms were detected in ACF by (19)F NMR. The chlorine in ACF does not exist as a separate, crystalline AlCl(3) phase. Additionally, chlorine-containing radicals, remaining from the synthesis, are trapped in cavities of ACF. These radicals are stable at room temperature but do not take part in the catalytic reaction.     

Synthesis of primary amines: first homogeneously catalyzed reductive amination with ammonia

[reaction: see text] The synthesis of primary amines via reductive amination of the corresponding carbonyl compounds with aqueous ammonia is achieved for the first time with soluble transition metal complexes. Up to an 86% yield and a 97% selectivity for benzylamines were obtained in the case of various benzaldehydes by using a Rh-catalyst together with water-soluble phosphine and ammonium acetate. In the case of aliphatic aldehydes, a bimetallic catalyst based on Rh/Ir gave improved results.     

Finding small somatic structural variants in exome sequencing data: a machine learning approach

Genetic variation forms the basis for diversity but can as well be harmful and cause diseases, such as tumors. Structural variants (SV) are an example of complex genetic variations that comprise of many nucleotides ranging up to several megabases. Based on recent developments in sequencing technology it has become feasable to elucidate the genetic state of a person’s genes (i.e. the exome) or even the complete genome. Here, a machine learning approach is presented to find small disease-related SVs with the help of sequencing data. The method uses differences in characteristics of mapping patterns between tumor and normal samples at a genomic locus. This way, the method aims to be directly applicable for exome sequencing data to improve detection of SVs since specific SV detection methods are currently lacking. The method has been evaluated based on a simulation study as well as with exome data of patients with acute myeloid leukemia. An implementation of the algorithm is available at https://github.com/lenz99-/svmod.     

The very strong solid Lewis acids aluminium chlorofluoride (ACF) and bromofluoride (ABF)—Synthesis, structure, and Lewis acidity

Aluminium chlorofluoride, ACF, (AlCl_xF_3−x, x ≈ 0.05-0.25) is an amorphous solid Lewis acid with an extraordinary acid strength that was patented by DuPont in 1992. It reaches the acidity of antimony pentafluoride, SbF₅, and, in some cases, even exceeds it.In this review, an overview of known structural data of ACF and the corresponding bromine compound, ABF, is presented, together with additional unpublished data. This includes a discussion of soft chemistry synthesis, structure of bulk and surface, and Lewis acidities of molecular and solid group 13 halides. The order of Lewis acidity of gaseous halides is established to be AlF_3(g) < AlCl_3(g) < AlBr_3(g) ≈ AlI_3(g) and AlX_3(g) > GaX_3(g) > InX_3(g) (X = F, Cl, Br, I).ACF and ABF are highly distorted solids. Different spectroscopic bulk methods show that the heavy halogen, chlorine or bromine, is a necessary perturbation that generates “disorder”. Highly Lewis acidic centres have been detected by several methods on the surface of ACF and ABF, which are responsible for the high catalytic reactivity observed in many reactions.The data gained on ACF and ABF show that many published data about heterogeneously catalysed fluorine-halogen exchange reactions in presence of aluminium chloride and bromide must be treated critically. In general, ACF and ABF are the active species.     

Rapid determination of polycyclic aromatic hydrocarbons in the exhaust gases of direct-injecting Diesel engines by HPLC

A rapid HPLC procedure is introduced that allows the quantification of polycyclic aromatic hydrocarbons (PAH) in the exhaust gases of direct injecting Diesel engines. A branch stream of the motor exhaust gas is passed through a cooler and a filter. Then the cooler rinsing phase and the soot collected on the filter are extracted with toluene. The clean-up is carried out by solid phase extraction and thin-layer chromatography. Using this method, which is reproducible with high precision, a great number of samples may be analysed in a cost and time efficient manner, even when other rapid procedures fail.     

A new condensation principle

We generalize (A), which was introduced in [Sch], to larger cardinals. For a regular cardinal >₀ we denote by (A) the statement that and for all regular >,is stationary in It was shown in [Sch] that can hold in a set-generic extension of L. We here prove that can hold in a set-generic extension of L as well. In both cases we in fact get equiconsistency theorems. This strengthens results of [Rä00] and [Rä01]. is equivalent with the existence of 0^#.Mathematics Subject Classification (1991): Primary 03E55, 03E15, Secondary 03E35, 03E60     

First total synthesis of the biologically active 2,7-dioxygenated tricyclic carbazole alkaloids 7-methoxy-O-methylmukonal, clausine H (clauszoline-C), clausine K (clauszoline-J) and clausine O

Using the iron-mediated arylamine cyclization as the key step we have achieved a short and highly efficient access to the biologically active 2,7-dioxygenated tricyclic carbazole alkaloids 7-methoxy-O-methylmukonal, clausine H (clauszoline-C), clausine K (clauszoline-J) and clausine O.     

Structure of (NH4)3GaF6 investigated by multinuclear magic-angle spinning NMR spectroscopy in comparison with rietveld refinement

The structure of ammonium gallium cryolite (NH(4))(3)GaF(6) was investigated by (19)F and (69,71)Ga magic-angle spinning (MAS) NMR in comparison with X-ray powder diffraction followed by Rietveld refinement. In agreement with previous thermodynamic measurements, NMR experiments on (NH(4))(3)GaF(6) support the model of rigid GaF(6) octahedra. At high spinning speeds (30 kHz), the scalar coupling between the six equivalent (19)F nuclei and (69,71)Ga can be directly observed in the powder spectra. The coupling constants are J(19)F(69)Ga = 197 Hz and J(19)F(71)Ga = 264 Hz. To explain the (71)Ga spectra recorded at 3 kHz a small distribution of quadrupolar frequencies has to be included. The spread of the spinning sidebands hints to a largest nu(Q) value of 28 kHz for (71)Ga. This can be explained by the occurrence of highly symmetric GaF(6) octahedra, which are tilted against the surrounding atoms. In addition, the incomplete motional excitation does not average out the quadrupolar effects. NMR findings are in discrepancy to those of Rietveld refinement. As result it appears that X-ray diffraction is not sensitive enough to deliver proper results.     

Transient Silenes as Versatile Synthons – The Reaction of Dichloromethyl‐tris(trimethylsilyl)silane with Organolithium Reagents

Treatment of dichloromethyl‐tris(trimethylsilyl)silane (Me₃Si)₃Si–CHCl₂ ( 1 ), prepared by the reaction of tris(trimethylsilyl)silane with chloroform in presence of potassium tertbutoxide, with organolithium reagents (molar ratio 1 : 3) affords the bis(trimethylsilyl)methyl‐disilanes Me₃SiSiR₂–CH(SiMe₃)₂ ( 12 a–d ) ( a : R = Me, b : R = n‐Bu, c : R = Ph, d : R = Mes). The formation of 12 a–d is discussed as proceeding through an exceptional series of isomerization and addition reactions involving intermediate silyl substituted carbenoids and transient silenes. The carbenoid (Me₃Si)₂PhSi–C(SiMe₃)LiCl ( 8 c ) is moderately stable at low temperature and was trapped with water to give (Me₃Si)₂PhSi–CH(SiMe₃)Cl ( 9 c ) and with chlorotrimethylsilane affording (Me₃Si)₂PhSi–CCl(SiMe₃)₂ ( 7 c ). For 12 d an X‐ray crystal structure analysis was performed, which characterizes the compound as a highly congested silane with bond parameters significantly deviating from standard values.