Ricardo J. Rodríguez

Diastereoselective synthesis of bulky, strongly nucleophilic, and configurationally stable P-stereogenic tricyclic phosphines.

A very simple, one-step highly diastereoselective synthesis of bulky, configurationally and air-stable P-chiral tricyclic phosphines 3, showing an exceptionally strong nucleophilic character, has been developed. This method involves the reaction of the stable phosphonium sila-ylide 1 with aryl- and alkyl-substituted acetylene derivatives. Starting from commercially available chiral (R,S)-(+)-endo-2-norborneol, the corresponding enantiomerically pure phosphines were obtained with excellent enantioselectivities (ee ≥ 99%) and high chemical yields.

Silacyclopropylideneplatinum(0) Complex as a Robust and Efficient Hydrosilylation Catalyst

The base-stabilized silacyclopropylidene 1 behaves as a versatile strongly nucleophilic ligand toward transition metals. The strong silylene-metal binding related to both increased σ-donating and π-accepting character of silylene 1 compared to N-heterocyclic carbenes (NHCs) allowed the synthesis of robust and air-stable silylene complexes. Of particular interest, the corresponding platinum(0) complex 6 exhibits high stability and a high level of selectivity and catalytic activity in hydrosilylation reactions that is superior to that of the related NHC-Pt(0) complexes.

Chiral transition-metal complexes as Brønsted-acid catalysts for the asymmetric Friedel–Crafts hydroxyalkylation of indoles

The Friedel-Crafts reaction between 3,3,3-trifluoropyruvates and indoles is efficiently catalysed by the iridium complex [(η(5)-C5Me5)Ir{(R)-Prophos}(H2O)][SbF6]2 (1) with up to 84% ee. Experimental data and theoretical calculations support a mechanism involving the Brønsted-acid activation of the pyruvate carbonyl by the protons of the coordinated water molecule in 1. Water is not dissociated during the process and, therefore, the catalytic reaction occurs with no direct interaction between the substrates and the metal.

Modelling and analysing resilience as a security issue within UML

Modelling system security is not common practise in software projects yet. Among other problems, there is not a widely accepted methodology which unifies the actual heterogeneity of security issues when addressing a whole security specification. Certainly, the reality is even worse since there is not an accepted or standard common notation for carrying out the security specification. In this work, we study how modelling security issues, specifically resilience, could be integrated in the MARTE-DAM framework, which allows the expression of performance and dependability requirements in UML models. We base this claim on the close relationship between security and dependability. Indeed, MARTE proposes a framework for non-functional properties specification (NFP), while DAM exploits it for dependability purposes. So, our goal is to take advantage of the common NFP framework while the dependability and security concerns are modelled in a unified view. On the other hand, we consider that the resulting security specification will be useful for developing model in which security related properties, such as availability, will be analysed. We will clarify these claims by means of an example.

Donor-Stabilized Silacyclobutanone: A Precursor of 1-Silaketene via Retro-[2 + 2]-Cycloaddition Reaction at Room Temperature

The synthesis of donor-stabilized silacyclobutanone 2 was successfully realized by the reaction of silacyclopropylidene 1 with benzaldehyde in the presence of a Lewis acid catalyst. Of particular interest, silacyclobutanone 2 evolves at room temperature via a retro-[2 + 2]-cycloaddition reaction, leading to an original NHC-stabilized 1-silaketene 4 and cis-stilbene.

On synergies of cyber and physical security modelling in vulnerability assessment of railway systems

Display Omitted Cyber-physical systems need holistic methods to discover relationships between physical and cyber components.Security threats attempt to both physical and cyber elements.Model-driven techniques accounting for joint physical and cyber-security modelling and evaluation are explored.Synergies between physical and cyber security UML profiles remarked in a case study of the railway domain. The multifaceted nature of cyber-physical systems needs holistic study methods to detect essential aspects and interrelations among physical and cyber components. Like the systems themselves, security threats feature both cyber and physical elements. Although to apply divide et impera approaches helps handling system complexity, to consider just one aspect at a time does not provide adequate risk awareness and hence does not allow to design the most appropriate countermeasures. To support this claim, in this paper we provide a joint application of two model-driven techniques for physical and cyber-security evaluation. We apply two UML profiles, namely SecAM (for cyber-security) and CIP_VAM (for physical security), in combination. In such a way, we demonstrate the synergy between both profiles and the need for their tighter integration in the context of a reference case study from the railway domain.

Temperature Dual Enantioselective Control in a Rhodium‐Catalyzed Michael‐Type Friedel–Crafts Reaction: A Mechanistic Explanation

By changing the temperature from 283 to 233 K, the S (99 % ee) or R (96 % ee) enantiomer of the Friedel-Crafts (FC) adduct of the reaction between N-methyl-2-methylindole and trans-β-nitrostyrene can be obtained by using (SRh ,RC )-[(η(5) -C5 Me5 )Rh{(R)-Prophos}(H2 O)][SbF6 ]2 as the catalyst precursor. This catalytic system presents two other uncommon features: 1) The ee changes with reaction time showing trends that depend on the reaction temperature and 2) an increase in the catalyst loading results in a decrease in the ee of the S enantiomer. Detection and characterization of the intermediate metal-nitroalkene and metal-aci-nitro complexes, the free aci-nitro compound, and the FC adduct-complex, together with solution NMR measurements, theoretical calculations, and kinetic studies have allowed us to propose two plausible alternative catalytic cycles. On the basis of these cycles, all the above-mentioned observations can be rationalized. In particular, the reversibility of one of the cycles together with the kinetic resolution of the intermediate aci-nitro complexes account for the high ee values achieved in both antipodes. On the other hand, the results of kinetic measurements explain the unusual effect of the increment in catalyst loading.

Fault-tolerant techniques and security mechanisms for model-based performance prediction of critical systems

Security attacks aim to system vulnerabilities that may lead to operational failures. In order to react to attacks software designers use to introduce Fault-Tolerant Techniques (FTTs), such as recovery procedures, and/or Security Mechanisms (SMs), such as encryption of data. FTTs and SMs inevitably consume system resources, hence they influence the system performance, even affecting its full operability. The goal of this paper is to provide a model-based methodology able to quantitatively estimate the performance degradation due to the introduction of FTTs and/or SMs aimed at protecting critical systems. Such a methodology is able to inform software designers about the performance degradation the system may incur, thus supporting them to find appropriate security strategies while meeting performance requirements. This approach has been applied to a case study in the E-commerce domain, whose experimental results demonstrate its effectiveness.

Modelling Security of Critical Infrastructures: A Survivability Assessment

Critical infrastructures, usually designed to handle disruptions caused by human errors or random acts of nature, define assets whose normal operation must be guaranteed to maintain its essential services for human daily living. Malicious intended attacks to these targets need to be considered during system design. To face with these situations, defense plans must be developed in advance. In this paper, we present a UML profile, named SecAM, that enables the modelling and security specification for critical infrastructures during the early phases (requirements, design) of systems development life-cycle. SecAM endows security assessment, through survivability analysis, of different security solutions before system deployment. As a case study, we evaluate the survivability of the Saudi Arabia crude-oil pipeline network under two different attack scenarios. The stochastic analysis, carried out with Generalized Stochastic Petri nets, quantitatively estimates the minimisation of attack damages into the crude-oil network.

PeabraiN: A PIPE Extension for Performance Estimation and Resource Optimisation

Many discrete systems with shared resources from different artificial domains (such as manufacturing, logistics or web services) can be modelled in terms of timed Petri nets. Two studies that may result of interest when dealing with such a systems are the performance evaluation (or completed jobs per unit of time) and the resource optimisation. Exact performance evaluation, however, may become unachievable due to the necessity of an exhaustive exploration of the state-space. In this context, a solution can be to estimate the performance by computing bounds. Resource optimisation leverages a budget and distributes resources in order to maximise the system performance. In this paper, we present Pea brain, a collection of PIPE tool-compliant modules for performance estimation and resource optimisation based on bounds computation for Stochastic Petri Nets. The algorithms supporting the modules make an intensive use of linear programming techniques and therefore their computational complexity is low. Besides, other PN properties, such as structural enabling bound at a transition, structural marking bound at a place or visit ratios computation, are added to PIPE tool as well.