bluuebunny/crossref_metadata_2025 huggingface dataset:
The design of a reinforced earth retaining wall at Dan-y-graig, Risca
Authors: Collins T. J.
Published: July 2007

The Paper describes the selection and design development of a reinforced earth solution to the problem of supporting a new dual carriageway routed over sidelong ground,14.5 m above and parallel to a fast-flowing river. A three-span bridge supported by piled intermediate piers and reinforced earth abutments was incorporated at about the third point of the 540 m long reinforced earth walls.

At one section of the scheme, where it was particularly desirable to minimize excavation into the side-long ground, a stepped form of wall cross-section was used. A method of sizing such a cross section is described together with illustrative examples of the design of reinforced earth retaining walls and abutments in submerged conditions.
Design approaches for geotextile separators beneath the granular sub-bases of unpaved roads
Authors: John N. W. M.
Published: July 2007

The purpose of a geotextile separator beneath a granular sub-baisse to prevent the road aggregate and the underlying subgrade soil from intermixing. In the absence of a geotextile, contamination of the sub-base aggregate by soft subgrade soil could reduce its load bearing capacity and thereby limit the life of the pavement

A number of different approaches have been proposed for the design of geotextile separators beneath unpaved roads. The most widely accepted of the methods based on simple hand calculations are those of Giroud and Noiray, and Sellmeijer et al. This Technical Note presents a simplified summary of these two design approaches and suggests some modifications.
Track quality improvement plan for London Underground
Authors: Sunley V. K. , Riley P. J.
Published: July 2007

Mr Sunley opened the discussion with his Paper, ‘Track quality improvement plan for London Underground’. He explained that the origins of the plan came from concern within London Underground over the consequences of poor track conditions.
Some examples of separation geotextiles under road pavements
Authors: Lawson C. R.
Published: July 2007

This Paper provides examples of the use of separators in road construction. It highlights aspects of function and cost saving and examines on-site construction procedure benefits prior to the construction of the road. It also highlights the essential differences in the separation function of a geotextile in temporary roads compared with that in permanent road structures
Electrification of British Railways' East Coast Main Line: Calton South Tunnel, Edinburgh, strengthening works for electrification
Authors: Riddell J. B.
Published: July 2007

Calton twin tunnels lie just east of Waverley Station Edinburgh. The North Tunnel carries a single line and was repaired in Tunnel was the subject of major strengthening works costing about £1.0 million and is the subject of this Paper. The 150 year old twin track tunnel is driven through a mixture of volcanic rocks and mudstones and has a fault passing through near its east portal. Large accessible voids were recorded above the crown's bricklining and evidence of several serious bulges of the lining were noted using photogrammetry. Distometer monitoring of these bulges revealed the need to support the lining in two locations. Rock bolting, grouting and guniting was used at one weak area whereas at the east end a tunnel-within-a-tunnel was constructed for 120 m using precast concrete segments. Extensive temporary works and careful monitoring of the tunnel structure was necessary to allow the invert rock excavation necessary to build the new ‘tube’ which catered for the operators' needs of an electrified single rail track.
M40 Oxford to Birmingham Route location and design
Authors: Heptinstall C. T. K. , Blood J. D.
Published: July 2007

The Institution of Highway Engineers submitted a scheme for a national motorway system to the Ministry of Transport in 1936 and a national motorway plan was produced by the County Surveyor's Society in 1938, including a motorway from London via Oxford to Birmingham. However, it was the early 1960s before work commenced on the first section of the M40 High Wycombe Bypass and it was 1974 before the last section of motorway between London and Oxford was opened to traffic.

This Paper describes the preparatory work and highway design for the continuation of the M40 northwards from Waterstock, near Oxford, to Birmingham.
An international initiative in highway research collaboration
Authors: Cornelius D. F.
Published: July 2007

This Paper describes the genesis of the Forum of European National Highway Research Laboratories(FEHRL) and TRL's leading role in its formation. FEHRL members are drawn from EC and EFTA countries. The Paper describes FEHRL's mission, to encourage collaboration between national highway research so as to provide relevant knowledge to governments, the road industry and road users. FEHRL's objectives are also given; to meet these objectives FEHRL has developed a Strategic European Road Research Programme (SERRP). This programme was submitted to the European Commission, which is considering how elements of a revised SERRP might be carried forward as part of the EC 4th R & D Framework Programme. SERRP is described in outline. It covers road-making materials, pavement design, roadside equipment, construction and maintenance, management, road/vehicle interaction and road environment.

Other FEHRL activities and their outcomes, such as the organization of a seminar on the falling weight deflectometer and a symposium on the mitigation of traffic noise in urban areas are summarized. Mention is made of the research collaboration that has been encouraged by FEHRL and which has led to strong cooperation between various groupings of its members on projects such as BRITE/EURAM. The Paper concludes with thoughts on the possible future for FEHRL.
Rail links into and out of the United Kingdom via the Channel Tunnel - opportunities and constraints
Authors: McLoughlin P. , Garnett C. , Robinson A. , Reid Sir Bob , Stewart R. S. C.
Published: July 2007

In his opening address, Patrick McLoughlin, MP, expressed his gratitude to the President of the Institution of Civil Engineers for providing the opportunity to discuss the impact of one of the greatest British and French engineering challenges.
Research needs in transport
Authors: Jones V. E. , Gore C. , Heyes M. P. H. , Ratcliffe B. G.
Published: July 2007

Mr Jones outlined the tasks of the Review of Transportation Research and Education Panel and explained that the breadth of the review was reflected in the composition of the panel. The review was timely because travel demand overall was increasing at a rate which was substantially faster than effective capacity would or could be expanded. Transport was operating near to capacity for a greater period of time and transport policies were increasingly preoccupied with demand management.
Runway resurfacing experiences
Authors: Austin G. E. , Davies W. S. , Evans K. G. , Sparkes A. M.
Published: July 2007

The speakers based their introductory remarks on the three papers published in ICE Proceedings Part 1, published June 1991.
Design and construction of the Dornoch Firth Bridge: design
Authors: Iversen N. , Faulds J. R. , Rowley F. N.
Published: July 2007

This Paper explains the history of the project, the design and construct competition, and the design process that the Contractors followed from the initial inquiry stage to the final permanent works design for an incrementally launched continuous prestressed concrete box superstructure, supported on 20 reinforced concrete portals.

The introduction describes how the final design was chosen. It includes reference to the influence that the economics, aesthetics and the programme implications of the various options considered had on the final chosen design and how the client's design brief was met.

The design aspects are dealt with under three separate headings: substructure, superstructure and bridgeworks finishings.

In each of these sections the Authors describe how the design criteria were met, how the method of construction influenced the design, and how the durability and maintenance aspects were incorporated.
Possible application of guided bus technology in Britain - operational design implications
Authors: Tebb R. G. P.
Published: July 2007

Guided bus is a transport concept which ought more properly to be termed ‘guidable bus’, because its essentlal characteristic is that the vehicles can operate steered on ordinary roads in the normal manner or can be guided wherever infrastructure is provided for this purpose. Guided bus is intended to bring together the best features of road and rail transport to provide a high-performance, highly reliable system offering origin-destination transport for the majority of users, in today's idiom, genuinely a seamless rapid transit system. Compared to ordinary busways, guided busways offer the opportunity for substantial reductions in the amount of space required and provlde an enhanced ride and performance.

Buses can be guided electronically or mechanically; although research on the current generatlon of guided buses started with electronic guidance, the greatest success has been achleved with mechanical guidance. In particular, the concept of kerb-guidance where the vehicle is steered by two 180 mm dia. solid rubber wheels in a bus lane provlded wlth 180 mm high kerbs set 2·6 m apart, has achieved greatest provenance with over 12 years of continuous operatlonal use. Because guidance need only be provided where congestion or circuitous road networks would otherwise delay buses the design of any system needs to explore localized opportunities as well as the overall system performance. Introduction can be incremental, as funds allow and needs require. The operational design implications for a guided bus system therefore are that great care needs to be taken in the application of a broad range of design features in a wide variety of potential applications to achieve the most cost-effective and efficient rapid transit system.
Cost-effective measurement of track for maintenance planning
Authors: Lewis R. B.
Published: July 2007

The equipment and techniques used by British Rail Research in their track recording car to detect rail defects are described. Inspections can be performed at 70 km/h on good quality continuously welded rail (CWR) in the Ultrasonic Test Unit (UTU). Computerization is improving the speed and efficiency of track maintenance.
Improvements to crossings
Authors: Sawley K. J.
Published: July 2007

This Technical Note outlines work done to assess objectively the relative merits of a number of fixed, acute, rail crossings, and summarizes the factors that affect crossing performance
Case Definitions for Use in Population‐Based Surveillance of Periodontitis
Authors: Page Roy C. , Eke Paul I.
Published: July 2007

Many definitions of periodontitis have been used in the literature for population‐based studies, but there is no accepted standard. In early epidemiologic studies, the two major periodontal diseases, gingivitis and periodontitis, were combined and considered to be a continuum. National United States surveys were conducted in 1960 to 1962, 1971 to 1974, 1981, 1985 to 1986, 1988 to 1994, and 1999 to 2000. The case definitions and protocols used in the six national surveys reflect a continuing evolution and improvement over time. Generally, the clinical diagnosis of periodontitis is based on measures of probing depth (PD), clinical attachment level (CAL), the radiographic pattern and extent of alveolar bone loss, gingival inflammation measured as bleeding on probing, or a combination of these measures. Several other patient characteristics are considered, and several factors, such as age, can affect measurements of PD and CAL. Accuracy and reproducibility of measurements of PD and CAL are important because case definitions for periodontitis are based largely on either or both measurements, and relatively small changes in these values can result in large changes in disease prevalence. The classification currently accepted by the American Academy of Periodontology (AAP) was devised by the 1999 International Workshop for a Classification of Periodontal Diseases and Conditions. However, in 2003 the Centers for Disease Control and Prevention and the AAP appointed a working group to develop further standardized clinical case definitions for population‐based studies of periodontitis. This classification defines severe periodontitis and moderate periodontitis in terms of PD and CAL to enhance case definitions and further demonstrates the importance of thresholds of PD and CAL and the number of affected sites when determining prevalence.
Detection of Porphyromonas gingivalis in the Amniotic Fluid in Pregnant Women With a Diagnosis of Threatened Premature Labor
Authors: León Rubén , Silva Nora , Ovalle Alfredo , Chaparro Alejandra , Ahumada Alexis , Gajardo Marta , Martinez Maria , Gamonal Jorge
Published: July 2007

Background: Epidemiologic and randomized controlled studies have shown that periodontal diseases may be associated with preterm labor and delivery of infants with low birth weights. The purpose of the present study was to determine the presence of microbial invasion of the amniotic cavity by periodontopathic bacteria in pregnant women with a diagnosis of threatened premature labor.

Methods: A periodontal examination and collection of amniotic fluid and subgingival plaque samples were performed on women identified as having threatened premature labor (preterm premature rupture of membranes without clinical infection or labor and preterm labor with intact membranes) and a gestational age ranging between 24 and 34 weeks. Samples collected from amniotic fluid and from the four deepest periodontal pockets in each patient were pooled in prereduced transport fluid and cultured. Porphyromonas gingivalis was identified primarily by colony morphology under stereoscopic microscope and rapid biochemical tests. Amniotic fluid or plaque samples were homogenized, DNA was extracted, and polymerase chain reaction (PCR) amplification of 16S rRNA with specific and universal primers was carried out.

Results: Twenty‐six women with threatened premature labor were included: eight with preterm premature rupture of membranes and 18 with preterm labor with intact membranes. Eight women presented with gingivitis, 12 with chronic periodontitis, and six without periodontal disease. Microbial invasion of the amniotic cavity as detected by P. gingivalis PCR was 30.8% (eight of 26 patients). In these eight patients, P. gingivalis was present in both the subgingival samples and the respective amniotic fluid sample.

Conclusion: The presence of microbial invasion of the amniotic cavity by P. gingivalis could indicate a role for periodontal pathogenic bacteria in pregnant women with a diagnosis of threatened premature labor.
Early Devonian calymenid larvae (Trilobita) from the Bissounel Formation (Montagne Noire, France)
Authors: Lerosey-Aubril Rudy
Published: July 2007

The late Emsian middle Member of the Bissounel Formation (Montagne Noire, France) has yielded a highly diverse silicified trilobite fauna. Among the thousands of disarticulated sclerites discovered, two protaspid specimens were found that display morphological characteristics of planktonic larvae of calymenid trilobites. The presence of calymenid protaspides within a non-calymenid trilobite fauna is noted. The two specimens are very similar to the first planktonic larval stage of the Ordovician Flexicalymene senaria (Conrad, 1841), and are of comparable size. This indicates that, as in F. senaria, a second planktonic larval stage might have occurred in the ontogeny of this undetermined calymenid. Thus, some post-Ordovician calymenids might have retained the ancestral developmental strategy with a two-stage planktonic period. The discovery of these two protaspides constitutes the first evidence of a calymenid trilobite in the Devonian of the Montagne Noire.
Distance Education vs Face-to-Face Classes: Individual Differences, Course Preferences and Enrollment
Authors: Harris Michael L. , Gibson Shanan G.
Published: July 2007

To understand better students' preferences for enrollment in distance education over face-to-face courses, the individual difference variables of sex, age category, class level, work status, number of distance education courses taken, frequency of computing technology usage, comfort with course management software, and comfort with computing technology were examined. Analysis indicated that older students, women, and those who work full time were more likely to enroll in distance education courses. Those who had taken the most distance education courses in the past and women were more likely to express a stated preference for distance education over face-to-face classes.
Anoxic alkaline oxidation of bisulfide by Fe/Ce oxides: Reaction pathway
Authors: Petre Catalin F. , Larachi Faïçal
Published: July 2007

The kinetics of the anoxic reaction between bisulfide and iron/cerium oxide–hydroxide was studied for alkaline pH [8.0–11.0] at 0.1 MPa and 298 K in a batch slurry reactor as a part and parcel of the surface chemistry in action in the oxidation of the total reduced sulfur pollutants in the pulp and paper atmospheric emissions. Bisulfide was converted into thiosulfate and polysulfides; while the leached divalent iron and thiosulfate dovetailed equimolarly for pH ≥ 9.5 which was attributed to the breaking of sulfur–oxygen surface intermediates initiated by iron‐disulfide FeII(SS) complexes. X‐ray photoelectron spectroscopy of S 2p and Fe 2p of the material revealed iron sulfide, polysulfides/elemental sulfur and thiosulfate signatures along with Fe(III) oxide–hydroxide, Fe(II) sulfide and some Fe(II) connected to sulfoxy species. A detailed reaction pathway of the anoxic oxidation of bisulfide by Fe/Ce oxide–hydroxide based on FeII(SS) complex was proposed for explaining the formation of zerovalent sulfur, thiosulfate, and leached ferrous iron, and whereof a kinetic model was derived to depict the Fe(II) leaching and bisulfide consumption rates. The model rate constants were analyzed in terms of sensitivity to pH, and initial concentrations of bisulfide and surface Fe(III). © 2007 American Institute of Chemical Engineers AIChE J, 2007
Reactions of [Cp*Ru(H2O)(NBD)]+ with alkynes
Authors: Xiong Wei‐Cheng , Yu Guang‐Ao , Gan Quan , Yin Jun , Meng Xiang‐Gao , Liu Sheng Hua
Published: July 2007

Formal [2 + 2 + 2] addition reactions of [Cp*Ru(H2O)(NBD)]BF4 (NBD = norbornadiene) with PhCCR (R = H, COOEt) give [Cp*Ru(η6‐C6H5C9H8R)] BF4 (1a, R = H; 2a, R = COOEt). Treatment of [Cp*Ru(H2O)(NBD)]BF4 with PhCCCCPh does not give [2 + 2 + 2] addition product, but [Cp*Ru(η6‐C6H5CCCCPh)] BF4(3a). Treatment of 1a, 2a, 3a with NaBPh4 affords [Cp*Ru(η6‐C6H5C9H8R)] BPh4 (1b, R = H; 2b, R = COOEt) and [Cp*Ru(η6‐C6H5CCCCPh)] BPh4(3b). The structures of 1b, 2b and 3b were determined by X‐ray crystallography. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and phase behavior of cholesteric liquid crystal polymers containing glutamic acid in main‐chain
Authors: Zhang Bao‐Yan , Zhang Li‐Feng , Tian Mei , Xiao Wen‐Qiang , Guan Yan
Published: July 2007

Four polymers (P0–P3) containing peptide chain as polymer backbone were synthesized by condensation reaction with bis(trichloromethyl)carbonate and triethylamine. The chemical structures of the monomers M0–M3 were confirmed by FTIR and 1H‐NMR. The structure–property relationships of the monomers and polymers are discussed. Their phase behavior and optical properties were investigated by differential scanning calorimetry, thermogravimetric analysis, and polarizing optical microscopy. Monomers M1–M3 and polymers P1–P3 displayed cholesteric phases. The results demonstrated that the melt temperature and clear point of monomers (M1–M3) and polymers (P1–P3) decreased with the increase of the flexible spacer length in the side‐chain, and the mesophase temperature range of the polymers increased with the increase of the flexible spacer length. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
A project‐based biochemistry laboratory promoting the understanding and uses of fluorescence spectroscopy in the study of biomolecular structures and interactions
Authors: Briese Nicholas , Jakubowski Henry V.
Published: July 2007

A laboratory project for a first semester biochemistry course is described, which integrates the traditional classroom study of the structure and function of biomolecules with the laboratory study of these molecules using fluorescence spectroscopy. Students are assigned a specific question addressing the stability/function of lipids, proteins, or nucleic acids, and asked to design an experiment to answer the question using fluorescence methodologies. Students study phase equilibria and determine the critical micelle concentration of single chain amphiphiles, the melting point of multilamellar vesicles, and the melting points and thermodynamic constants (Keq, ΔG0, ΔH0 and ΔS0) for denaturation of ds‐DNA and proteins. In addition, they examine binding properties of proteins. These laboratory experiments are designed to support student learning of the major themes of structure and function in the course.
From purines to basic biochemical concepts
Authors: Marini Isabella , Ipata Piero Luigi
Published: July 2007

Many high school biology courses address mainly the molecular and cellular basis of life. The complexity that underlies the most essential processes is often difficult for the students to understand; possibly, in part, because of the inability to see and explore them. Six simple practical experiments on purine catabolism as a part of a biochemistry course for 16–18 years students that require only simple equipment for thin layer chromatography have been developed, tried, and tested. These include detection and measurement of enzyme activities in biological extracts, detection of reversible and irreversible reactions, creating a pathway from consecutive reactions. They focus on purines because of their multifunctionality in biochemical processes. They allow students to grasp specific concepts and to use them as a framework for approaching metabolic complexity.
Locks and keys
Authors: Orgill MaryKay , Bodner George
Published: July 2007

Analogies can be powerful teaching tools because they can make abstract material intelligible to students by comparing it to material with which the students are already familiar. In this study, we interviewed 43 students to determine the specific ways they use analogies to learn and function in their biochemistry classes. We found that students use analogies in a variety of unique ways to promote understanding, visualization, recall, and motivation in their biochemistry clases. However, their uses of analogies did not always correlate well with their instructors' purposes for using analogies. We also discuss the teaching implications of these findings.
Problem‐solving Test: α1‐antitrypsin deficiency
Authors: Szeberényi József
Published: July 2007

Terms to be familiar with before you start to solve the test: protein conformation, protein folding, proteases, protein synthesis, protein glycosylation, glycoproteins, N‐linked and O‐linked oligosaccharides, endoplasmic reticulum, Golgi complex, secretory pathway, microsomes, pulse/chase labeling, SDS‐polyacrylamide gel electrophoresis, immunoprecipitation, chaperones, protein translocation.
CC‐Doppelbindungen mit extremer Reaktivität, II. 1,3‐Diphenyl‐2‐imidazolidinselenon aus 1,1′,3,3′‐Tetraphenyl‐Δ2,2′‐biimidazolidin und Selen
Authors: Schönberg Alexander , Singer Erich , Stephan Werner
Published: July 2007

1,1′,3,3′‐Tetraphenyl‐Δ2,2′‐biimidazolidin (1) reagiert mit metallischem Selen unter Bildung von 1,3‐Diphenyl‐2‐imidazolidinselenon (6). Die Einwirkung von Kupferpulver, Ethyliodid, Thiophenol, Phenylmagnesiumbromid, Phenylisocyanat und Lithiumalanat auf 6 wird beschrieben. Die teils ungewöhnlichen Abläufe dieser Reaktion werden diskutiert.
Diels‐Alder‐Addukte des 1,7‐Dehydroquadricyclans
Authors: Baumgärtel Otto , Harnisch Joachim , Szeimies Günter , Van Meerssche Maurice , Germain Gabriel , Declercq Jean‐Paul
Published: July 2007

Nach Einwirkung von sperrigen Lithiumamiden auf 1‐Chlorquadricyclan in Gegenwart von Anthracen, 9‐Methoxyanthracen, 2,5‐Dimethylfuran, Furan oder 1,2,3‐Trimethylisoindol isolierte man die entsprechenden Diels‐Alder‐Addukte des 1,7‐Dehydroquadricyclans 4a, 4b, 8a, 10 und 17 in befriedigenden bis guten Ausbeuten. Die Konstitution von 4a wurde durch Röntgenstrukturanalyse gesichert. Versuche zur Isomerisierung des Quadricyclan‐Teils der Addukte zu der entsprechenden Norbornadien‐Einheit lieferten nur polymeres Material. Thiophenol addierte sich selektiv an die zentrale Propellan‐Bindung von 4a zum Thioether 28a. Acetylendicarbonsäuredimethylester und Azodicarbonsäure‐diethylester reagierten am Quadricyclan‐System von 17 unter Bildung der Brückenkopfolefine 24 und 25.
Thermolabile Kohlenwasserstoffe, XXI. Zusammenhänge zwischen thermischer Stabilität und Spannung nichtsymmetrisch hochverzweigter Kohlenwasserstoffe
Authors: Hellmann Siegried , Beckhaus Hans‐Dieter , Rüchardt Christoph
Published: July 2007

Die thermische Zerfallsreaktion von 20 Kohlenwasserstoffen 3 zu den Radikalen 4 und tert‐Butylradikalen (5) wurde präparativ und kinetisch untersucht. Die früher für die thermische Spaltung symmetrisch substituierter C  C‐Bindungen festgestellten quantitativen Beziehungen zwischen den freien Aktivierungsenthalpien und den Spannungsenthalpien können auf unsymmetrisch substituierte C  C‐Bindungen übertragen werden. Die Einführung des Begriffs der „Dissoziationsspannung”︁ (Differenz von Grundzustandsspannung und Restspannung in den radikalischen Bruchstücken) hat sich als besonders vorteilhaft erwiesen. Durch einfache Kraftfeldrechnungen kann nun die thermische Spaltungsgeschwindigkeit der meisten einfachen aliphatischen CC‐Bindungen vorausgesagt werden.
Reaktionen von Komplexliganden, XXIII. Bis(phosphino)inden‐Derivate durch CC‐Verknüpfung von Arylcarben‐Liganden und Bis(diphenylphosphino)acetylen
Authors: Dötz Karl Heinz , Pruskil Ingrid , Schubert Ulrich , Ackermann Klaus
Published: July 2007

Pentacarbonyl(methoxyphenylcarben)‐Komplexe des Chroms und Wolframs (1a, 2a) reagieren mit Bis(diphenylphosphino)acetylen (3) unter CO‐Substitution zu den zweikernigen alkin‐verbrückten Bis(carben)‐Komplexen (CO)4[CH3O(C6H5) C]M‐[(C6H5)2P‐C  C‐P(C6H5)2]‐M(CO)4[C(OCH3)C65](4a, 5a). Die Chrom‐Verbindung 4a wird beim Erwärmen in den Tetracarbonyl [1,2‐bis(phosphino)inden]chrom‐Komplex 6a und 1a gespalten. Aus den Arylcarben‐Chrom‐Komplexen (CO)5Cr[Cp‐RC6H4)OCH3] (R;H, CH3, CF3) (1a‐c) und 3 entstehen direkt die 1,2‐Bis(phosphino)inden‐Derivate 6a–c. Der Molekülbau von 6c wird durch eine Röntgenstrukturanalyse belegt.
Versuche zur Darstellung von Derivaten des 2,3‐Diazabicyclo[2.2.2]octa‐5,7‐diens
Authors: Askani Rainer , Schneider Wilfried
Published: July 2007

Die 2,3‐Diazabicyclo[2.2.2]octa‐5,7‐dien‐Derivate 1a und b konnten weder über die Photoaromatisierung von 8 noch über die anodische Oxidation der Dicarbonsäure 13a, b erhalten werden. Cycloadditionen an 21 führten zu Derivaten des Titelsystems, die bereits oberhalb −10°C einer [4+2]‐Cycloreversion unter Bildung der Tetrahydrophthalazine 22 unterliegen. Die thermische Umwandlung von 21 und 22 verläuft nach einem Kettenmechanismus.
Triphosphetanone, die ersten cyclischen Phosphaharnstoffderivate mit Vierring‐Struktur
Authors: Appel Rolf , Paulen Wilfried
Published: July 2007

Triphosphetanones, the First Cyclic Phospha‐Urea Derivatives with Four Ring Structure

The reaction of the 1,3‐bis(trimethylsilyl)substituted diphospha‐urea derivative 1 with dichlorophosphanes leads to cyclisation with formation of the four‐membered triphosphetanones 4. A characteristic feature of the new class of compounds is the CO‐elimination by sun‐light.
Eine einfache Synthese von 3‐Methoxypyridin und seinen Analogen durch Alkylierungsreaktionen
Authors: Finkentey Christel , Langhals Elke , Langhals Heinz
Published: July 2007

A Simple Synthesis of 3‐Methoxypyridine and of Analogues by Alkylation Reactions

Solid potassiumhydroxide in dimethylsulfoxide has high basicity but only low nucleophilicity and is used as a base for the methylation of 3‐hydroxypridine (1) and of analogues with methyliodide. The reaction is not interferred by the addition of small amounts of water and gives yields of 40 percent for the reaction of 1 and up to 100 percent for analogues. The described reagent therefore may be an alternative to lithium diisopropylamide.
3‐Metallierte Enamine, X Erzeugung und Reaktivität von 1‐(Diethoxyphosphoryl)‐1‐(dimethylamino)allyl‐Anionen
Authors: Ahlbrecht Hubertus , Farnung Winfried
Published: July 2007

Die 1‐Phosphorylenamine 8 und 10 reagieren nach Deprotonierung als Anion 8A und 10A regio‐und stereoselektiv mit Silylierungs‐ und Alkylierungsmitteln zu homologen (E)‐1‐Phosphorylenaminen 13, 15, 19 – 32. Diese lassen sich zu den entsprechenden in 3‐Stellung alkylierten Carbonsäuren hydrolysieren. Bei 10 erfolgt die Deprotonierung stets an der zur Phosphorylgruppe cis‐ständigen Methylgruppe. Anschließend isomerisiert das primär gebildete Allyl‐Anion rasch um die C‐1 – C‐2‐Bindung. Diese hohe Regio‐ und Stereoselektivität der Deprotonierung gestattet die gezielte Einführung von bis zu drei verschiedenen Alkylgruppen. Die Ergebnisse der NMR‐spektroskopischen Untersuchung von 8A und 10A werden diskutiert.
Übergangsmetall‐Methylen‐Komplexe, XLII. Formylmethylen‐Brücken in Eisen‐, Cobalt‐ und Rhodium‐Komplexen
Authors: Kalcher Willibald , Herrmann Wolfgang A. , Pahl Claudia , Ziegler Manfred L.
Published: July 2007

Formyldiazomethan (α‐Diazoacetaldehyd; 1) reagiert mit den zweikernigen, Metall‐Metall‐Doppelbindungen aufweisenden Eisen‐, Cobalt‐ und Rhodium‐Komplexen 2a – c) ohne Nebenreaktionen unter N2‐Eliminierung zu den formylsubstituierten Dimetallacyclopropanen 3a – c), deren Geometrie für das Rhodium‐Derivat 3c durch Kristallstrukturanalyse ermittelt wurde.
Darstellung und Eigenschaften von und Reaktionen mit metallhaltigen Heterocyclen, XXXI. Vergleichende Studien über drei‐, vier‐ und fünfgliedrige Phosphamolybda‐ und ‐wolframacycloalkane
Authors: Lindner Ekkehard , Küster Ernst Ulrich , Hiller Wolfgang , Fawzi Riad
Published: July 2007

Durch Reduktion von LnBrMoPPh2H (1a) [LnMo = (η5‐C5H5)Mo(CO)2 (a)] mit Natrium in THF erhält man das neuartige Phosphidomolybdat Na2[LnMoPPh2] (2a) mit zwei nucleophilen Zentren, welches mit (CH3O)2SO2 das Methylderivat LnCH3MoPPh2CH3 (7a) liefert. Die Einwirkung der geminalen Dichloride Cl2CHR auf 2a führt zu den Phosphamolybdacyclopropanen LnM⊓oPPh2⊓CHR (8, 8′a) [R = H (8a), CH3 (8′a)]. Nach einer Röntgenstrukturuntersuchung kristallisiert 8a in der monoklinen Raumgruppe P21/c mit Z = 4, besitzt einen ziemlich kurzen P – C‐Abstand (ca. 174 pm) und zeigt in Lösung dynamisches Verhalten. Die für die Rotation der „side‐on”︁‐gebundenen CH2 – PPh2‐Gruppe notwendige Freie Aktivierungsenthalpie berechnet sich aus den 1H‐NMR‐Spektren zu δG± = 53.9 kJ/mol. Durch reduktive Cyclisierung der aus LnXMCO (3a, b) [LnM = (η5‐C5H5)W(CO)2 (b)] und den Liganden Ph2P – [CH2]n – Cl erhaltenen Intermediate LnXMPPh2 – [CH2]n – Cl (4b, 5, 6a, b) [n = 1 (4), 2 (5), 3 (6)] mit Natriumamalgam, sind die drei‐bis fünfgliedrigen Metallacycloalkane Ln–MPPh2–[CH2]n (8b, 9, 10a, b) zugänglich. Im Gegensatz zu 8a läßt sich in die Mo – C‐Bindung von 9, 10a SO2 einschieben unter Bildung der cyclischen Sulfinato‐S‐Komplexe LnMoPPh2 – [CH2]n –So2 (11, 12a) [n = 2 (11a), 3 (12a)].
Synthese und dynamisches Verhalten von Pentamethyl‐cyclopentadienylphosphanen
Authors: Jutzi Peter , Saleske Hartmut
Published: July 2007

Durch Umsetzung von Pentamethylcyclopentadienyl(Me5cp)‐lithium mit Halogenphosphanen werden die Me5cp‐Phosphane 1 – 5, 7, 8, 11, 12, 14, 15 und 19 – 24 hergestellt. Substitutionsreaktionen an den Me5cp‐Halogenphosphanen 7 und 14 führen zu den Me5cp‐Phosphanen 6, 9, 10, 13 und 16 – 18. Diese Moleküle besitzen eine fluktuierende Struktur aufgrund von 1,5‐sigmatropen Umlagerungen der jeweiligen Phosphorgruppierung. Durch 1H‐NMR‐Untersuchungen und Linienformanalysen wird gezeigt, daß die phosphorständigen Liganden die Geschwindigkeit dieser Umlagerungen drastisch beeinflussen (Aktivierungsenergien zwischen 5 und 31 kcal/mol).
[3.3]‐ and [4.4](2,7)Pyrenophanes as Excimer Models: Synthesis, Molecular Structure, and Spectroscopic Properties
Authors: Staab Heinz A. , Riegler Norbert , Diederich François , Krieger Claus , Schweitzer Dieter
Published: July 2007

As excimer models the [3.3]‐ and [4.4]pyrenophanes 1 and 2 were synthesized. As the key precursor for the synthesis of 1 the octahydro‐dithia[4.4]pyrenophane 9 was obtained by cyclisation of 4 and 8, the syntheses of which are described. Disulfone 10, derived from 9, on vapour‐phase pyrolysis yielded 11 which by dehydrogenation was converted into 1. In an analogous route 2 was obtained via 16, 17, and 18 starting from 4 and 15 (prepared in the reaction sequence 12 → 13 → 14 → 15). – The molecular structures of 1 and 2, determined by X‐ray structure analyses, are discussed with regard to transanular distances and deviations from planarity of the pyrene units. – Absorption spectra of 1 and 2 are discussed with reference to transanular interactions. The fluorescence emissions of 1 and 2 are found to be ‘excimer‐like’. Results obtained by ODMR measurements of 1 are reported.
Röntgenstruktur von Tetraphenylarsonium‐tetraazidoaurat(III)1)
Authors: Beck Wolfgang , Nöth Heinrich
Published: July 2007

X‐Ray Structure Analysis of Tetraphenylarsonium Tetraazidoaurate(III)

The title compound 1 crystallizes in the tetragonal space group P4/n with As and Au in special positions. Four nitrogen atoms surround the Au atom in a square, and the Au(N3)4− anion adopts a whirlwind configuration. The N3− group is asymmetic (N1 – N2 122 pm, N2 – N3 115 pm), typical for covalently bound azido ligands.
Über die Enantioselektive Adsorption chiraler Azofarbstoffe an Seide, Wolle, Stärke und Cellulose
Authors: Konrad Gerd , Musso Hans
Published: July 2007

Enantioselective Adsorption of Chiral Azo Dyestuffs on Silk and Wool as well as Starch and Cellulose

The racemic azo compounds 1 or 2 from diazotised m‐amino mandelic acid and β‐naphthol could not even slightly be resolved by adsorption on wool as it has been reported. On powdered silk and potato starch 2 was resolved partly by chromatography. All attempts with the amide 3 from 1‐phenylethylamine and p‐azobenzenecarboxylic acid have not been successful so far.
Komplexe mit alkylsubstituierten Phosphinomethanen und ‐methaniden, VII1). Mono‐ und Diphosphinomethanide als Chelatliganden in Eisen‐, Cobalt‐ und Nickelkomplexen
Authors: Karsch Hans Heinz
Published: July 2007

Pentakoordinierte Komplexe (1a, b, L = L' = PMe3; L = PMe3, L' = CO) und Y (2a, b, Y = Cl, PF6) sowie hexakoordinierte Komplexe (3, 4, X = H, Me) und (5) wurden durch Reaktion von LiCH2PMe2 mit den entsprechenden Phosphanmetallhalogenid‐Komplexen dargestellt. Alle Komplexe enthalten einen ‐Dreiring. Demgegenüber führt die analoge Reaktion mit LiCH(PMe2)2 zu den Komplexen L3(H)Fe(Me2PCHPMe2) (7) und L2Me2Co(Me2) (9), die einen Vierring enthalten. Hierzu im Gegensatz steht der Cobalt(I)‐Komplex (6b), der wie 1a, b einen dreigliedrigen Ring mit einer „freien”︁ exocyclischen Me2P‐Gruppe aufweist. Die spontane Umlagerung von 7 in L3Fe(Me2PCH2PMe2) (8) durch reduktive Eliminierung verläft wahrscheinlich ebenfalls über einen solchen Dreiring, und auch 9 läßt sich bei Substitution von PMe3 durch PMe2Ph ( = L' ) in einen Dreiringkomplex (10) überführen.
Koordinative Wechselwirkungen in Chelatkomplexen des Siliciums, 91). Über die Kristallstrukturbestimmung und den Mechanismus von Austauschvorgängen am fünffach koordinierten Silicium
Authors: Klebe Gerhard , Nix Marianne , Hensen Karl
Published: July 2007

Die Kristallstrukturbestimmung des 2‐{[Methyl(trifluorsilyl)amino]methyl}pyridins (2b) zeigt Si, bedingt durch eine intramolekulare Lewissäure‐Base‐Wechselwirkung, in trigonal‐bipyramidaler Geometrie (Si…N‐Adduktbindung: 197.4(6)pm, Si – N‐„Einfachbindung”︁: 170.1(10)pm). Unter – 10°C wird in Lösung dieser Aufbau NMR‐spektroskopisch bestätigt. In eng verwandten Si‐Komplexen des Benzyldimethylamins weisen die NMR‐Spektren auf einen isostrukturellen Aufbau bei tiefen Temperaturen hin. In allen Verbindungen treten mit steigender Temperatur zunehmend rascher werdende Austauschvorgänge der Substituenten am Silicium auf. Durch die labil werdende Adduktbindung ändert sich während des Austausches der Koordinationszustand des Si, und der Platzwechsel der Substituenten erfolgt über eine Drehbewegung des zwischenzeitlich tetragonalisierten Silylrestes. Die Äquilibrierungsbarrieren zeigen, daß die koordinativen Wechselwirkungen im vorliegenden Fall als relativ schwach zu bezeichnen sind.
Verknüpfung von Metallocenen in Serie: Cp2V – CpFeCp – VCp2
Authors: Köhler Frank H. , Geike Walter A. , Hofmann Peter , Schubert Ulrich , Stauffert Peter
Published: July 2007

Die Verbrückung von paramagnetischen (RC5H4)2V‐Teilen durch Ferrocen ergab die Titelverbindung 1 (R = H) sowie 2 (R = CH3). 2 wurde durch Massenspektroskopie und Elementaranalyse charakterisiert. Eine detaillierte paramagnetische NMR‐Untersuchung von 1 und 2 zeigte die Stereochemie in Lösung und die elektronischen Verhältnisse auf: Die Vanadocen‐ und Ferrocen‐Teile stehen senkrecht zueinander; ein Austausch ungepaarter Elektronen über das Ferrocen kann bis hinunter zu 234 K nicht beobachtet werden. Eine niedrigere Symmetrie, jedoch dieselbe Verknüpfung der drei Metallocene, wurde in der Röntgenstrukturanalyse beobachtet. Die Ferrocenbrücke ist stark in Richtung einer ungewöhnlichen η4‐Situation der Cp‐Ringe verzerrt. Es wurden Extenden‐Hückel‐MO‐Rechnungen durchgeführt, die die NMR‐Daten und die Röntgenstruktur, insbesondere die ziemlich lange (217.1 pm) V – C‐Bindung erklären.
Brückenkopf‐gekoppelte Bicyclo[1.1.0]butane: Darstellung und Eigenschaften
Authors: Röumer Roland , Harnisch Joachim , Röder Andrea , Schöffer Agnes , Szeimies Güunter , Germain Gabriel , Arrieta Juan Manuel
Published: July 2007

Die Verknüpfung von zwei oder drei Tricyclo[4.1.0.02,7]heptan‐ oder Tricyclo[3.1.0.02,6]hexan‐Einheiten zu den Kupplungsdimeren und ‐trimeren 9a, 10a, 13, 14 und 15 gelang außer durch Cuprat‐Oxidation durch die Anlagerung der Brückenkopf‐lithiierten Derivate 5c, 6c, 9b und 10b an die gespannte CC‐Doppelbindung des Tricycloheptens 7 und des Tricyclohexans 8. Während die Thermolyse und die Silberionen‐katalysierte Umlagerung von 9a zum Di‐cyclohexenylacetylen 16a führen, liefern HX‐Additionen an 9a Binorpinyliden‐Derivate vom Typ 24 und 25, die auch durch Reduktionsreaktionen von 9a gebildet werden. Die Konstitutionen von zwei ausgewählten Folgeprodukten von 9a, vom Acetat 24a und von der Spiro‐Verbindung 31a, wurden durch Röntgenstrukturanalysen gesichert. Die CC‐Doppelbindung in 24a ist trans‐pyramidalisiert.
Darstellung und Röntgenstrukturanalyse des Diels‐Alder‐Addukts von 4‐Phenyl‐4H‐1,2,4‐triazol‐3,5‐dion an Octavalen
Authors: Christl Manfred , Lang Reinhard , Reimann Wolfgang , Irngartinger Hermann
Published: July 2007

Aus Octavalen (1) und 4‐Phenyl‐4H‐1,2,4‐triazol‐3,5‐dion bildet sich das Diels‐Alder‐Addukt 2. Seine Röntgenstrukturanalyse ergab für das Bicyclo[1.1.0]butan‐Gerüst, dessen 2‐ und 4‐Stellung durch vier Atome überbrückt sind, einen Interplanarwinkel von 122.7°. Die Brückenbindung C1 – C3 hat eine Länge von 1.487 Å.
Synthesis and Structures of as‐Triazinoquinazolines, I
Authors: Abdel‐Hady Sayed A. L. , Badawy Mohamed A. , Ibrahim Yehia A. , Pfleiderer Wolfgang
Published: July 2007

3‐(Methyltio)‐6‐R‐1,2,4‐triazin‐5(2H)‐ones 1 – 6 have been converted into the 3‐R‐2H‐as‐tri‐azino[3,2‐b]quinazoline‐2,6(1H)‐diones 8 – 13 upon cyclocondensation with anthranilic acid. Reaction of 2‐methyl‐3‐(methylthio)‐6‐phenyl‐1,2,4‐triazin‐5(2H)‐one (23) with anthranilic acid gave 1‐methyl‐3‐phenyl‐2H‐as‐triazino[3,4‐b]quinoazoline‐4,69 (1H)‐dione (29) via the intermediate 26. N‐Methylanthranilic acid and 2 or 5 afforded the 11‐methyl‐3‐R‐2H‐as‐triazino[3,2‐b]quinazoline‐2,6(11H)‐diones 36 and 38, respectively.
Übergangsmetallkomplexe instabiler Ylide, III. Präparative, stereochemische und mechanistische Aspekte bei der koordinationschemischen Stabilisierung instabiler Ylid‐Chelatliganden
Authors: Weber Lothar , Wewers Dietmar
Published: July 2007

Der Schwefelylid‐Komplex (CO)5Cr[CH2S(O)Me2] (1) bildet mit den unsymmetrisch substituierten Diphosphanen bzw. Arsanen R12E1CH2E2R22 (4a – d) regioselektiv die Chelatkomplexe 5a – d, bei denen das stärker nucleophile Ende von 4 als Oniumfunktion auftritt. Demgegenüber reagiert (CO)4Cr[CH2S(O)Me2]2 (2) mit 4a – d regioselektiv zu den isomeren Chelatkomplexen 6a – d, in denen die stärker nucleophile Donorfunktion von 4 am Chromatom gebunden ist.
Übergangsmetall‐Methylen‐Komplexe, XLIII. Drei‐ und viergliedrige Dimetallacyclen mit Schwefeldioxid, Selen, Chlorogold und einem Silberdiazoalkan als Molekülbausteinen
Authors: Herrmann Wolfgang A. , Bauer Christine , Weichmann Josef
Published: July 2007

Schwefeldioxid addiert sich als vorzüglicher π‐Ligand unter schonenden Reaktionsbedingungen (–80… +25°C) rasch und übersichtlich an Metall‐Metall‐Doppelbindungen unter Bildung beständiger 1:1‐Addukte, in denen stets SO2‐Brücken vorliegen. Ausgehend von den zweifach verbrückten Metall‐Metall‐Doppelbindungen der zweikernigen Organorhodium‐ und cobalt‐Komplexe 1a, b, 3 und 5 entstehen unter teilweiser Konstitutionsisomerisierung der Brückenliganden die neuen μ‐SO2‐Komplexe 2a, b, 4 bzw. 6. Durch glatt verlaufende elektrophile Ringerweiterungsreaktionen der μ‐Methylen‐Komplexe 7a, b sind die ersten μ‐(Thioformaldehyd‐S,S‐dioxid‐C,S)‐Komplexe 8a, b zugänglich. Mit elementarem Selen (9a), Carbonyl(chloro)gold (9b) und dem Silberdiazoalkan 9c bildet 1a die dreigliedrigen Ringsysteme 10a – c.
Anodische Oxidation von Organoborverbindungen
Authors: Schlegel Günter , Schäfer Hans J.
Published: July 2007

Organoborane werden durch Nucleophile in leichter oxidierbare Borate übergeführt und die Alkylreste durch anodische Oxidation dimerisiert. Die Oxidationspotentiale (Ep) der Borate werden stark vom komplexierenden Nucleophil beeinflußt, z. B. Ep = +0.37V (gKE) mit OH− oder + 1.65 V mit Tetrahydrofuran. Mit Trioctylboran (5) werden die Dimerenausbeuten (10) durch Variation von Elektrodenmaterial und Elektrolyt optimiert. An der Platinanode in KOH‐Methanol/Tetrahydrofuran liegen die Ausbeuten für acyclische Alkylreste um 80%, die für Cycloalkane niedriger. Sie übertreffen die der Kolbe‐Elektrolyse oder der Oxidation mit neutralem Wasserstoffperoxid und sind denen bei der Oxidation mit Silbernitrat vergleichbar. – Die selektive Darstellung unsymmetrischer Produkte aus Boraten mit unterschiedlichen Alkylresten gelingt nicht; die Dimerisierung verläuft wahrscheinlich über freie Radikale, die statistisch kuppeln. Gute Ausbeuten an unsymmetrischen Kupplungsprodukten werden jedoch erzielt, wenn ein Olefin im Überschuß eingesetzt wird. Mit chlor‐, ether‐, ester‐ und arylsubstituierten Alkylresten erhält man Dimere mit 21 – 66% Ausbeute. Mit Bromiden gelingt die Kupplung schlecht, mit Nitrilen überhaupt nicht.
Heterocyclische Verbindungen, VI. Bildung von Isomeren bei der Acylierung von Verbindungen mit 1‐Aryl‐4‐methyl‐5H‐2,3‐benzodiazepin‐Skelett
Authors: Körösi Jenö , Láng Tibor , Sohár Pál , Neszmélyi András , Horváth Gyula , Zólyomi Gábor
Published: July 2007

Bei der Acetylierung von 1‐(3,4‐Dimethoxyphenyl)‐5‐ethyl‐7,8‐dimethoxy‐4‐methyl‐5H‐2,3‐benzodiazepin (1)2,3) mit heißem Acetanhydrid werden die Isomeren 2a und 3a im Verhältnis von ≈︁ 1:1 gebildet. Die Acetylierung von 1 in Gegenwart von Pyridin führt ausschließlich zu 2a5), die des Hydrochlorids von 1(4)2,6) in heißem Acetanhydrid ausschließlich zu 3a. 2a und 3a können nicht ineinander umgewandelt werden, doch kann 3a aus 2a über 5 dargestellt werden. Während 3a beständig gegen wäßrige Hydrolyse ist, wird unter denselben Bedingungen 2a durch Ringöffnung in 7a übergeführt. Mittels Propionsäureanhydrid wurden 2b, 3b und 7b und mittels Benzoesäureanhydrid 3c synthetisiert. Für die Zuordnung des 13C‐NMR‐Spektrums von 3a wurden 13C‐markiertes 1 (17) und 3a (18) hergestellt. Für die Acetylierung von 5H‐2,3‐Benzodiazepin‐Basen und ihrer Salze werden noch weitere Beispiele angegeben (22 – 26).
Diazadiene als Steuerliganden in der homogenen Katalyse, VII. Katalytische Darstellung und Struktur eines doppelt vicinal substituierten Cyclooctatetraens – 1,4,5,8‐Tetrakis[(p‐tolyloxy)methyl]‐1,3,5,7‐cyclooctatetraen
Authors: Diercks Rainer , Stamp Lutz , Dieck Heindirk Tom
Published: July 2007

Die katalytische Umsetzung von 2‐Propinyl‐p‐tolylether (Propargyl‐p‐tolylether) mit dem Diazadien‐nickelkomplex 4 führt zu einem hochsymmetrischen Cyclooctatetraenderivat 2. 1H‐NMR‐ und 13C‐NMR‐Spektren erlauben aus Symmetriegründen keine Unterscheidung zwischen drei möglichen Substitutionsmusten (1,3,5,7; 1,4,5,8; 1,2,5,6). Durch eine Röntgenstrukturanalyse wurden die Substituentenstellung und die Lage der Doppelbindungen bestimmt. Das gefundene, doppelt vicinale 1,4,5,8‐Substitutionsmuster war für katalytisch dargestellte Cyclooctatertraene bis jetzt unbekannt; zugleich ist 2 das erste Cyclotetramere eines Propargylethers.
Die Hydrierung substituierter 1,1‐Cyclopropandicarbonitrile
Authors: Neumann Norbert , Boldt Peter
Published: July 2007

Bei der katalytischen Hydrierung von 2‐Butyl‐, 2,2‐Dimethyl‐ und 2,2,3‐Trimethyl‐1,1‐cyclopropandicarbonitril (1 – 3) findet entsprechend der Regel von Musso et al. 2) Ringöffnung an der C‐1 – C‐3‐Bindung statt. Zwei hochsubstituierte Cyclopropane (10, 12) gaben keine hydrogenolytische Ringspaltung.
Fluorierungen von Adamantanderivaten mit Sauerstoffdifluorid
Authors: Bolte Gerd , Haas Alois
Published: July 2007

Fluorination of Adamantane Derivatives with Oxygen Difluoride

Fluorination of adamantane and adamantane derivatives 1 with OF2 in the absence of an HF‐trap gives fluoroadamantanes 2 and adamantanols 3 in varying amounts. Increasing yields of 2 are obtained in the presence of Na2CO3 as an HF‐trap. In addition, the fluorooxahomoadamantanes 4b and e are formed in this reaction. The fluorination of adamantanone (5) with OF2 leads to analogous products.
Umsetzungen von Metall‐ und Metalloidverbindungen mit mehrfunktionellen Molekülen, XXXVIII. Reaktion von Ethandiamiden mit Bromdimethylboran
Authors: Maringgele Walter , Sheldrick George M. , Meller Anton , Noltemeyer Mathias
Published: July 2007

Es werden Reaktionen symmetrisch substituierter N,N′‐Dialkyl‐(Diaryl)ethandiamide A mit Bromdimethylboran untersucht. Die Reaktion im Molverhältnis 1 : 2 führt zu 2,6‐Dioxonia‐4,8‐diaza‐3,7‐diboratabicyclo[3.3.0]octanen 1a – j, N,N′‐Bis(dimethylboryl)‐N,N′‐diorganylethandiamiden 4a, b und den Gleichgewichtsmischungen 3a – d. Als Nebenprodukte treten 2‐Oxonia‐4‐oxa‐6‐azonia‐8‐aza‐3,7‐diboratabicyclo[3.3.0]octane 2a – j auf. Bei der Umsetzung von N,N′‐Diorganylethandiamiden mit Bromdimethylboran im Molverhältnis 1 : 1 erhält man die 1‐Oxonia‐3‐aza‐2‐boratacyclopentan‐4‐on‐Derivate 5a – e, N‐(Dimethylboryl)‐N,N′‐diorganylethandiamide 6a – c, Gleichgewichtsmischungen 7a – d und 5‐(Alkylamino)‐4‐(alkylimonio)‐2,2‐dimethyl‐1‐oxonia‐3‐oxa‐2‐boratacyclopenta n‐bromide 8a – h. Für 1a, 5a, e und 8 b wurden Röntgenstrukturanalysen durchgeführt.
Hetero‐π‐Systeme, 9. Über die Beziehungen zwischen Silaethenen und Methylsilylenen
Authors: Maier Günther , Mihm Gerhard , Reisenauer Hans Peter , Littmann Dieter
Published: July 2007

Die Silaolefine 1 und dazu isomeren Methylsilylene 2 sind getrennt existenzfähige Spezies, lassen sich in einer Argonmatrix aber über eine photochemisch induzierte 1,2‐H‐Wanderung leicht ineinander umwandeln. Bei thermischer Anregung in der Gasphase ist sowohl die Isomerisierung eines Silaolefins zum zugehörigen Silylen (1d → 2d) als auch eines Silylens zum entsprechenden Silen (2f → 1f) direkt spektroskopisch nachweisbar.