New Synthesis and Chirality of (−)-4,4,4,4′,4′,4′-Hexafluorovaline

(?)-(R)-4,4,4,4′,4′,4′-Hexafluorovaline hydrochloride ((R)- 5 ) of 98% ee is prepared from β,β-bis(trifluoromethyl)acrylic acid (= benzyl 4,4,4-trifluoro-3-(trifluoromethyl)but-2-enoate; 1 ) in 4 steps with an overall yield of 9.6%. Key step is the separation of the TsOH salts of the diastereoisomers obtained by anti-Michael addition of (+)-(R)-1-phenylethylamine ( 2 ) to 1 (→ (R,R)- 3 ). In contrast to the published (S)-chirality, the X-ray structure analysis of (R,S)- 6 reveals, that (R)-chirality has to be assigned to the levorotatory (?)-4,4,4,4′,4′,4′-hexafluorovaline hydrochloride.     

Comparison of magnetic resonance imaging of inhaled SF6 with respiratory gas analysis

Magnetic resonance imaging of inhaled fluorinated inert gases ((19)F-MRI) such as sulfur hexafluoride (SF(6)) allows for analysis of ventilated air spaces. In this study, the possibility of using this technique to image lung function was assessed. For this, (19)F-MRI of inhaled SF(6) was compared with respiratory gas analysis, which is a global but reliable measure of alveolar gas fraction. Five anesthetized pigs underwent multiple-breath wash-in procedures with a gas mixture of 70% SF(6) and 30% oxygen. Two-dimensional (19)F-MRI and end-expiratory gas fraction analysis were performed after 4 to 24 inhaled breaths. Signal intensity of (19)F-MRI and end-expiratory SF(6) fraction were evaluated with respect to linear correlation and reproducibility. Time constants were estimated by both MRI and respiratory gas analysis data and compared for agreement. A good linear correlation between signal intensity and end-expiratory gas fraction was found (correlation coefficient 0.99+/-0.01). The data were reproducible (standard error of signal intensity 8% vs. that of gas fraction 5%) and the comparison of time constants yielded a sufficient agreement. According to the good linear correlation and the acceptable reproducibility, we suggest the (19)F-MRI to be a valuable tool for quantification of intrapulmonary SF(6) and hence lung function.     

Electrooxidation of pyrrole-terminated self-assembled lipoic acid derivatives

New pyrrole derivatives, pyrrolyl lipoic acid (Py-LA 3) and dipyrrolyl lipoic acid (Py₂-LA 2) have been used for surface attachment and immobilisation on gold surfaces, by self-assembly. The electrooxidation of the surface-confined pyrroles was analysed by cyclic voltammetry and the modified electrodes morphological and thickness changes addressed by scanning probe microscopy and ellipsometry. The data support the formation of oligomers as a result of the pendant-pyrrolyl units ease oxidation but provide no evidence of an effective subsequent polymerisation.     

Spatial mode cleaning by femtosecond filamentation in air

By studying the conical emission of a blue femtosecond laser filament in air, it is shown that self-improvement of the beams' spatial mode quality occurs for a self-guided laser pulse.     

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen: V. Synthese,reaktionen und struktur neuartiger manganacycloalkane

The colourless, six- and seven-membered manganacycloalkanes (OC)₄$\text{MnPR}{}_2\text{OCH}{}_2\text{XC}$H₂ are obtained by reaction of Na₂[(OC)₄MnPR₂O] with the bis(triflate)alkanes (YCH₂)₂X (R = C₆H₅; X = CH₂, C(CH₃)₂, CH₂CH₂; Y = CF₃SO₃). CO or SO₂ can be inserted into the reactive MnC-σ bonds under ring expansion. Some characteristic IR and ¹H NMR data are discussed. (OC)₄$\text{MnPR}{}_2\text{OCH}{}_2\text{CH}{}_2\text{C}$H₂ crystallizes monoclinic in the space group P2₁/c with Z = 4.     

Memory for the locations of environmental sounds

The accuracy with which a single source of sound can be localized has been examined in many studies, but very few studies have examined the ability of participants to determine the absolute locations of multiple sources of sound. The current study assessed participants' abilities to determine and remember the locations of up to six sources of environmental sound that were positioned at a range of azimuths and elevations in virtual auditory space. In experiment 1, a sequence of one to six sounds was presented one, three, or five times in each trial and the target sound was nominated following presentation of the last sequence. In experiment 2, memory load was held constant by nominating the target sound prior to a single sequence presentation. Localization accuracy was observed to decrease as the number of sounds was increased to three or more under the conditions of experiment 1, but not those of experiment 2. In experiment 1, localization was more accurate when sequences were presented more than once. Pronounced primacy and recency effects were observed for the six sound conditions in experiment 1. An analysis of errors for those conditions indicated that immediate temporal errors, but not immediate spatial errors, were over-represented.     

Inverse angle dependence of the reflection colours of cholesteric polymeric liquid crystals mixed with pigments

Measurements on thin layers of cholesteric liquid crystals with a cyclic polysiloxane backbone show the usual angle dependence of the reflection wavelength, namely a shift to shorter wavelengths with increasing angle of observation. By mixing these liquid-crystalline side chain polymers with suitable pigments or dyes or by choice of a suitable coloured background, a red shift of the reflection colour with increasing angle can be obtained.     

Entropy-Induced Selectivity Switch in Gold Catalysis: Fast Access to Indolo[1,2-a]quinolines

New N-heterocyclic compounds for organic functional materials and their efficient syntheses are highly demanded. A surprising entropy-induced selectivity switch in the gold-catalyzed intramolecular hydroarylation of 2-ethynyl N-aryl indoles was found and its exploitation led to straightforward syntheses of indolo[1,2-a]quinolines. Experimental and computational mechanistic investigations gave insight into this uncommon selectivity phenomenon and into the special reactivity of the indolo[1,2-a]quinolines. The high functional group tolerance of this methodology enabled access to a diverse scope with high yields. In addition, bidirectional approaches, post-functionalization reactions, and π-extension of the core structure were feasible. An in-depth study of the photophysical properties explored the structure-effect relationship for different derivatives and revealed a high potential of these compounds for future applications as functional materials.