Synthesis of Oxazines by Palladium Catalyzed Reductive Cyclization of Nitroarenes and Dienes Using Phenyl Formate as CO Surrogate

The synthesis of hetero-Diels-Alder adducts derived from nitrosoarenes as dienophiles (oxazines) has been the focus of much attention in recent years, since these products have pharmacological activity themselves or can be easily transformed into other products. 1 However, their usual synthesis requires problematic intermediate isolation of nitroso compounds. We have previously reported a method for oxazines synthesis in up to 91% yields in one pot by the reaction of unfunctionalized dienes with nitroarenes and carbon monoxide.2 Despite the high efficiency of this synthetic procedure, it has not become of widespread use by the chemical community. This is mostly because it involves the use of pressurized CO, requiring safety measures that are not available in most synthetic organic laboratories. To overcome this limitation, we started investigating the use of molecules capable of releasing CO in situ, thus avoiding the need for high-pressure equipment and CO lines. Recently, we have reported3 an efficient, convenient and general synthetic procedure to produce nitrogen heterocycles from nitro compounds in presence of a Pd catalyst employing phenyl formate as the CO releasing agent. In this study, we take advantage of this general procedure in the synthesis of oxazines from dienes and nitroarenes (Figure 1). First, due to its high cost, the amount of the diene was optimized down to 1:4 nitroarene to diene ratio. The reaction works well for nitroarenes bearing either electron-donating or electron-withdrawing substituents, a moderate steric hindrance on the nitroarene is well tolerated and yields up to 99% in one pot were reached. In addition, variation in the diene were also investigated using 2,3-dimethoxy-1,3-butadiene, isoprene and myrcene affording the corresponding oxazines in good yields

FAR INFRARED Ge DETECTORS: CONDUCTION AND ABSORPTION MECHANISMS

PhDThis report describes an experimental study of the conduction and absorption mechanisms of Germanium in the temperature range 4.2 - 1.5 K. The results of these studies were mainly devoted to the developments of very far infrared detectors. Germanium (Ge) is a well-known semiconductor element used widely, when doped with small concentration of impurities, for detection of far infrared wavelengths up to 100~m. For doping concentrations less 16 3 than 1.0 x 10 atoms/em, the absorption of radiation in the range 100- 1000~m is very weak Because of the lack of the proper absorption mechanisms, except for some photo-hopping absorption in compensated samples around 1000llm.16 -3 In the range of doping between 1-8 x 10 cm ,there exists additional thermal activation energy not present in the lower concentrations. It was thought that this activation energy results from impurity interactions in this doping range, and hence a delocalized energy band is thus formed above the ground state level. However, the electrical conduction, the width of this band and its position, and the relevance of this band to the marked bolometric effect for 10o-lOOOWU wavelength detections are not yet clear. This thesis presents further study on this band together with its relation to the conduction and absorption mechanisms. Comparative studies were usually made for two samples of Ge differing in doping configuration, one of which does not have this additional activation energy (low concentration) . The firs two chapters give a review of the absorption and conduction mechanisms in Ge at low temperatures, and the performance relations and measurements for different types of infrared detectors. In this report, the conduction mechanism is studied for the two samples, and includes galvanometric properties, thermal properties and energy scattering processes for the carriers in the delocalized band. The absorption characteristics, 1n lOO-lOOO~ru range of the two samples were investigated. Germanium elements with absorbing surfaces are also studied using two different techniques, namely, surface ion implantation and metal film deposition. The mutual effects of the implanted surface and the bulk material are discussed and suggestions for the future of this technique are given. Finally, the design and performance of the constructed high sensitivity far infrared Ge detectors using the higher concentration sample are given. Theoretical noise limitations were reached in these detectors. Heasurements and practicaI. astronomical applications are also given.Ministry of Higher Education, Egyp

Synthesis of 3,6-Dihydro-2H-[1, 2]-Oxazines from Nitroarenes and Conjugated Dienes, Catalyzed by Palladium/Phenanthroline Complexes and Employing Phenyl Formate as a CO Surrogate

Palladium/phenanthroline catalyzed reduction of nitroarenes by in situ-generated carbon monoxide, from the decomposition of phenyl formate, affords the corresponding nitrosoarenes. The latter are trapped by conjugated dienes to give the corresponding 3,6-dihydro-2H-[1, 2]-oxazines (hetero Diels-Alder adducts). Many functional groups are well tolerated. Yields are higher than those obtainable by any previously reported method, including the direct reaction of the diene with the pure nitrosoarene. The reaction can be performed in a single standard glass pressure tube, without the need for autoclaves or high-pressure CO lines

Global Verification and Analysis of Network Access Control Configuration

Network devices such as routers, firewalls, IPSec gateways, and NAT are configured using access control lists. However, recent studies and ISP surveys show that the management of access control configurations is a highly complex and error prone task. Without automated global configuration management tools, unreachablility and insecurity problems due to the misconfiguration of network devices become an ever more likely. In this report, we present a novel approach that models the global end-to-end behavior of access control devices in the network including routers, firewalls, NAT, IPSec gateways for unicast and multicast packets. Our model represents the network as a state machine where the packet header and location determine the state. The transitions in this model are determined by packet header information, packet location, and policy semantics for the devices being modeled. We encode the semantics of access control policies with Boolean functions using binary decision diagrams (BDDs). We extended computation tree logic (CTL) to provide more useful operators and then we use CTL and symbolic model checking to investigate all future and past states of this packet in the network and verify network reachability and security requirements. The model is implemented in a tool called ConfigChecker. We gave special consideration to ensure an efficient and scalable implementation. Our extensive evaluation study with various network and policy sizes shows that ConfigChecker has acceptable computation and space requirements with large number of nodes and configuration rules

Synthesis of nitrogen heterocycles by intramolecular cyclization of nitro-olefins attached to five-membered heterocycles, catalyzed by palladium complexes and with carbon monoxide as the reductant

Research in our unit recently showed that reductive cyclization of beta-nitrostyrenes catalyzed by palladium/phenanthroline complexes and with CO as a reductant affords indoles in good yields. The reaction proceeds by the activation of an aryl C-H bond. We decided to extend such cyclization reaction to other heterocyclic systems, although it is known that the activation of a C-H bond of electron-rich five member heterocycles is a more difficult reaction. Nitro olefins attached to 5-membered heterocyclic compounds were prepared by the Henry reaction and fully characterized by 1H-NMR, 13C-NMR and elemental and mass analyses. Subsequent reductive cyclization catalysed by palladium-phenanthroline complexes under CO pressure afforded a 10 pi-aromatic compounds, isoelectronic with pentalenyl dianion, and containing a pyrrole ring fused to another 5-membered heterocyclic compound. Compound was chosen as a model compound for the optimization of the experimental conditions. Among many tested ligands 4,7-dimethoxyphenanthroline showed good results for both conversion and selectivity. The optimization of temperature, CO pressure, nature of the base, type of ligand, reaction time and solvent are in progress

Formal Firewall Conformance Testing: An Application of Test and Proof Techniques

Firewalls are an important means to secure critical ICT infrastructures. As configurable off-the-shelf prod\-ucts, the effectiveness of a firewall crucially depends on both the correctness of the implementation itself as well as the correct configuration. While testing the implementation can be done once by the manufacturer, the configuration needs to be tested for each application individually. This is particularly challenging as the configuration, implementing a firewall policy, is inherently complex, hard to understand, administrated by different stakeholders and thus difficult to validate. This paper presents a formal model of both stateless and stateful firewalls (packet filters), including NAT, to which a specification-based conformance test case gen\-eration approach is applied. Furthermore, a verified optimisation technique for this approach is presented: starting from a formal model for stateless firewalls, a collection of semantics-preserving policy transformation rules and an algorithm that optimizes the specification with respect of the number of test cases required for path coverage of the model are derived. We extend an existing approach that integrates verification and testing, that is, tests and proofs to support conformance testing of network policies. The presented approach is supported by a test framework that allows to test actual firewalls using the test cases generated on the basis of the formal model. Finally, a report on several larger case studies is presented

On the Use of Formal Languages/Models for The Specification Verification, and Enforcement of Network Access-Lists

Complexity of access-lists and the diversity of their specifications are continuously increasing. Stating the high level requirements as well as verification of the implemented policies became an impossible task if human intervention is required. Also, proving the soundness of these inter-related and confusing policies is very hard without an appropriate framework. Therefore, a formal and canonical specification for security access-lists is highly needed for us to be able to specify requirements, verify correctness and enforce the policy