bluuebunny/crossref_metadata_2025 huggingface dataset:
External Technology Sourcing Through Alliances or Acquisitions: An Analysis of the Application-Specific Integrated Circuits Industry
Authors: Vanhaverbeke Wim , Duysters Geert , Noorderhaven Niels
Published: January 2003

In today's turbulent business environment innovation is the result of the interplay between two distinct but related factors: endogenous R&D efforts and (quasi) external acquisition of technology and know-how. Given the increasing importance of innovation, it is vital to understand more about the alternative mechanism—such as alliances and acquisitions—that can be used to enhance the innovative performance of companies. Most of the literature has dealt with these alternatives as isolated issues. Companies, however, are constantly challenged to choose between acquisitions and strategic alliances, given the limited resources that can be spent on research and development. This paper contributes to the literature because it focuses on the choice between innovation-related alliances and acquisitions. We focus on the question of how the trade-off between strategic alliances and acquisitions is influenced by previous direct and indirect ties between firms in an industry network of interfirm alliances. We formulate hypotheses pertaining to the number of direct ties between two companies, their proximity in the overall alliance network, and their centrality in that network. In so doing, we distinguish between ties that connect firms from the same and from different industry segments, and those that connect firms from the same or from different world regions. These hypotheses are tested on a sample of strategic alliances and acquisitions in the application-specific integrated circuits (ASIC) industry. The findings show that a series of strategic alliances between two partners increases the probability that one will ultimately acquire the other. Whereas previous direct contacts tend to lead to an acquisition, this is not true of previous indirect contacts, which increase the probability that a link between the companies, once it is forged, takes the form of a strategic alliance. In the case of acquisitions, firms that are more centrally located in the network of interfirm alliances tend to be acquirers, and firms with a less central position tend to become acquired. These findings underscore the importance of taking previously formed interfirm linkages into account when explaining the choice between strategic alliances and acquisitions, as these existing links influence the transaction costs associated with both alternatives.
Incentives and Computing Systems for Team-Based Organizations: A Mathematical and Economic Analysis
Authors: Merlone Ugo
Published: January 2003

This paper provides a mathematical and economic analysis “Incentives and Computing Systems for Team-Based Organizations” by A. Barua, C. H. Sophie Lee, and A. B. Whinston, which was published in Organization Science in 1995. Several points were not adequately stated in the original article and one of the key definitions is not clear, nor is it in keeping with the classical theory of production. Although the Cobb-Douglas production function is often used in the article, it does not comply with the article's definitions. The two main contributions of this paper are (1) to provide a word of caution to other readers who might try to extend Barua et al. (1995) and (2) to suggest alternative formulations and directions for future research.
Composite Variable Formulations for Express Shipment Service Network Design
Authors: Armacost Andrew P. , Barnhart Cynthia , Ware Keith A.
Published: January 2003

In this paper we describe a new approach to solving the express shipment service network design problem. Conventional polyhedral methods for network design and network loading problems do not consistently solve instances of the planning problem we consider. Under a restricted version of the problem, we transform conventional formulations to a new formulation using what we term composite variables. By removing flow decisions as explicit decisions, this extended formulation is cast purely in terms of the design elements. We establish that its linear programming relaxation gives stronger lower bounds than conventional approaches. We apply this composite variable formulation approach to the UPS Next Day Air delivery network and demonstrate potential annual cost savings in the hundreds of millions of dollars.
Deterministic Order-Up-To Level Policies in an Inventory Routing Problem
Authors: Bertazzi Luca , Paletta Giuseppe , Speranza M. Grazia
Published: January 2003

We consider a distribution problem in which a set of products has to be shipped from a supplier to several retailers in a given time horizon. Shipments from the supplier to the retailers are performed by a vehicle of given capacity and cost. Each retailer determines a minimum and a maximum level of the inventory of each product, and each must be visited before its inventory reaches the minimum level. Every time a retailer is visited, the quantity of each product delivered by the supplier is such that the maximum level of the inventory is reached at the retailer. The problem is to determine for each discrete time instant the retailers to be visited and the route of the vehicle. Various objective functions corresponding to different decision policies, and possibly to different decision makers, are considered. We present a heuristic algorithm and compare the solutions obtained with the different objective functions on a set of randomly generated problem instances.
An Adaptive Dynamic Programming Algorithm for Dynamic Fleet Management, I: Single Period Travel Times
Authors: Godfrey Gregory A. , Powell Warren B.
Published: January 2003

We consider a stochastic version of a dynamic resource allocation problem. In this setting, reusable resources must be assigned to tasks that arise randomly over time. We solve the problem using an adaptive dynamic programming algorithm that uses nonlinear functional approximations that give the value of resources in the future. Our functional approximations are piecewise linear and naturally provide integer solutions. We show that the approximations provide near-optimal solutions to deterministic problems and solutions that significantly outperform deterministic rolling-horizon methods on stochastic problems.
An Adaptive Dynamic Programming Algorithm for Dynamic Fleet Management, II: Multiperiod Travel Times
Authors: Godfrey Gregory A. , Powell Warren B.
Published: January 2003

In a companion paper (Godfrey and Powell 2002) we introduced an adaptive dynamic programming algorithm for stochastic dynamic resource allocation problems, which arise in the context of logistics and distribution, fleet management, and other allocation problems. The method depends on estimating separable nonlinear approximations of value functions, using a dynamic programming framework. That paper considered only the case in which the time to complete an action was always a single time period. Experiments with this technique quickly showed that when the basic algorithm was applied to problems with multiperiod travel times, the results were very poor. In this paper, we illustrate why this behavior arose, and propose a modified algorithm that addresses the issue. Experimental work demonstrates that the modified algorithm works on problems with multiperiod travel times, with results that are almost as good as the original algorithm applied to single period travel times.
A Heuristic Algorithm for the Auto-Carrier Transportation Problem
Authors: Tadei R. , Perboli G. , Della Croce F.
Published: January 2003

The delivery of vehicles to dealers is one of the major tasks in the vehicle production industry. It has relied on transportation companies that use special tractor-trailer trucks called auto-carriers. One of the main problems these companies have to solve is the optimal loading and routing of the auto-carriers, referred to as the Auto-Carrier Transportation (ACT) problem. In this paper we provide an integer programming formulation of the ACT problem and show that the problem is NP-hard in the strong sense. A three-step heuristic procedure stronglybased on the IP formulation, which considers loading, vehicle selection, and routing aspects, is proposed. An application to a real case studyof a vehicle transportation company located in northern Italyis given, with an average deviation lower than 3% from an upper bound on the optimal solution value.
Analysis and Algorithms for the Transtainer Routing Problem in Container Port Operations
Authors: Narasimhan Ananthapadmanabhan , Palekar Udatta S.
Published: January 2003

The problem of minimizing the time taken to load the containers from the container stack yard onto the ship is called the transtainer routing problem. We first do a theoretical investigation of the problem to understand the structural properties of the problem. We then use these results to prove that the problem is NP-Complete. The problem is then formulated as an integer program. A branch-and-bound based enumerative method is developed to obtain an exact solution to the problem. An algorithm to solve the matching problem on a line at the root node of the branch-and-bound tree is developed. Several lower bounds to prune the size of the tree are also developed. A result which states that there cannot exist a polynomial time heuristic with a bounded worst case unless P = NP is proved. Based on this result, an enumerative heuristic with a worst-case performance ratio of 1.5 is designed. Computational tests on randomly generated problems are conducted to evaluate the exact and heuristic algorithms.
Interblock Crane Deployment in Container Terminals
Authors: Cheung Raymond K. , Li Chung-Lun , Lin Wuqin
Published: January 2003

We consider the problem of scheduling the movements of cranes in a container storage yard so as to minimize the total unfinished workload at the end of each time period. The problem is formulated as a mixed-integer linear program, and the computational complexity ofthe problem is analyzed. A Lagrangian decomposition solution procedure is described. A new solution approach, called the successive piecewise-linear approximation method, is also developed. Through computational experiments, we show that our proposed solution methods are both efficient and effective for large-sized problems.
The Stochastic Inventory Routing Problem with Direct Deliveries
Authors: Kleywegt Anton J. , Nori Vijay S. , Savelsbergh Martin W. P.
Published: January 2003

Vendor managed inventory replenishment is a business practice in which vendors monitor their customers' inventories, and decide when and how much inventory should be replenished. The inventory routing problem addresses the coordination of inventory management and transportation. The ability to solve the inventory routing problem contributes to the realization of the potential savings in inventory and transportation costs brought about by vendor managed inventory replenishment. The inventory routing problem is hard, especially if a large number of customers is involved. We formulate the inventory routing problem as a Markov decision process, and we propose approximation methods to find good solutions with reasonable computational effort. Computational results are presented for the inventory routing problem with direct deliveries.
A Second Order Stochastic Network Equilibrium Model, II: Solution Method and Numerical Experiments
Authors: Watling David
Published: January 2003

Real traffic networks typically exhibit considerable day-to-day variations in traffic flows and travel times, yet these variations are commonly neglected in network performance models. Recently, two alternative theoretical approaches were proposed for incorporating stochastic flow variation in the equilibration of route choices: the stochastic process (SP) approach (Cantarella and Cascetta 1995) and the second order generalized stochastic user equilibrium (GSUE(2)) model (Watling 2002). The theoretical basis of the two approaches is contrasted, and the paper goes on to present a heuristic solution method for the GSUE(2) model, and two alternative simulation methods for the SP model, each applicable to the realistic case of probit-based choice probabilities. These solution methods are then applied to two realistic networks. Factors affecting convergence and reproducibility are first identified, followed by comparisons of the GSUE(2) and SP predictions. It is seen that a quasi-periodic behaviour commonly arises in the SP model, with the predictions radically different from the GSUE(2) model. However, by modifying the link performance functions in the overcapacity regime, the nature of the SP solution changes, and for a memory filter based on a large number of days' experience, its moments are seen to be approximated by those of the GSUE(2) model. Implications for the application of these models are discussed.
Estimation and Prediction of Time-Dependent Origin-Destination Flows with a Stochastic Mapping to Path Flows and Link Flows
Authors: Ashok K. , Ben-Akiva M. E.
Published: January 2003

This paper presents a new suite of models for the estimation and prediction of time-dependent Origin-Destination (O-D) matrices. The key contribution of the proposed approach is the explicit modeling and estimation of the dynamic mapping (the assignment matrix) between time-dependent O-D flows and link volumes. The assignment matrix depends upon underlying travel times and route choice fractions in the network. Since the travel times and route choice fractions are not known with certainty, the assignment matrix is prone to error. The proposed approach provides a systematic way of modeling this uncertainty to address both the offline and real-time versions of the O-D estimation/prediction problem. Preliminary empirical results indicate that generalized models with a stochastic assignment matrix could provide better results compared to conventional models with a fixed matrix.
Itinerary-Based Airline Fleet Assignment
Authors: Barnhart Cynthia , Kniker Timothy S. , Lohatepanont Manoj
Published: January 2003

We consider the airline fleet assignment problem involving the profit maximizing assignment of aircraft types to flight legs. Although several basic formulations have been proposed, important network considerations are insufficiently treated in these formulations and the resulting solutions are often suboptimal. We propose a new formulation and solution approach that captures network effects and generates superior solutions. We quantify the benefits of our proposed approach in a case study using data from a major United States airline.
A Heuristic Search Approach for a Nonstationary Stochastic Shortest Path Problem with Terminal Cost
Authors: Bander James L. , White Chelsea C.
Published: January 2003

We present a best-first heuristic search approach for determining an optimal policy for a stochastic shortest path problem. A vehicle is to travel from an origin, starting at time t0, to a destination, where once the destination is reached a terminal cost is accrued. The terminal cost depends on the time of arrival. Travel time along each arc in the network is modeled as a random variable with a distribution dependent on the time that travel along the arc is begun. The objective is to determine a routing policy that minimizes expected total cost. A routing policy is a rule that assigns the next arc to traverse, given the current node and time.

The heuristic search algorithm that we specialize to this stochastic problem is AO*. We demonstrate the significant computational advantages of AO*, relative to dynamic programming, on the basis of run time and storage, using a 131-intersection network of the major roads in Cleveland, Ohio. Further computational experience is based on grid networks that were randomly generated to have characteristics similar to transportation networks, and on randomly generated unstructured networks.
An Adaptive Dynamic Programming Algorithm for the Heterogeneous Resource Allocation Problem
Authors: Powell Warren B. , Shapiro Joel A. , Simão Hugo P.
Published: January 2003

We consider an aggregated version of a large-scale driver scheduling problem, derived from an application in less-than-truckload trucking, as a dynamic resource allocation problem. Drivers are aggregated into groups characterized by an attribute vector which capture the important attributes required to incorporate the work rules. The problem is very large: over 5,000 drivers and 30,000 loads in a four-day planning horizon. We formulate a problem that we call the heterogeneous resource allocation problem, which is more general than a classical multicommodity flow problem. Since the tasks have one-sided time windows, the problem is too large to even solve an LP relaxation. We formulate the problem as a multistage dynamic program and solve it using adaptive dynamic programming techniques. Since our problem is too large to solve using commercial solvers, we propose three independent benchmarks and demonstrate that our technique appears to be providing high-quality solutions in a reasonable amount of time.
A Branch-and-Cut Procedure for the Vehicle Routing Problem with Time Windows
Authors: Bard Jonathan F. , Kontoravdis George , Yu Gang
Published: January 2003

This paper addresses the problem of finding the minimum number of vehicles required to visit a set of nodes subject to time window and capacity constraints. The fleet is homogeneous and is located at a common depot. Each node requires the same type of service. An exact method is introduced based on branch and cut. In the computations, ever increasing lower bounds on the optimal solution are obtained by solving a series of relaxed problems that incorporate newly found valid inequalities. Feasible solutions or upper bounds are obtained with the help of greedy randomized adaptive search procedure (GRASP). A wide variety of cuts is introduced to tighten the linear programming (LP) relaxation of the original mixed-integer program. To find violated cuts, it is necessary to solve a separation problem. A substantial portion of the paper is aimed at describing the heuristics developed for this purpose. A new approach for obtaining feasible solutions from the LP relaxation is also discussed. Numerical results for standard 50- and 100-node benchmark problems are reported.
A Stochastic Model of Airline Operations
Authors: Rosenberger Jay M. , Schaefer Andrew J. , Goldsman David , Johnson Ellis L. , Kleywegt Anton J. , Nemhauser George L.
Published: January 2003

We present a stochastic model of the daily operations of an airline. Its primary purpose is to evaluate plans, such as crew schedules, as well as recovery policies in a random environment. We describe the structure of the stochastic model, sources of disruptions, recovery policies, and performance measures. Then, we describe SimAir—our simulation implementation of the stochastic model, and we give computational results. Finally, we give future directions for the study of airline recovery policies and planning under uncertainty.
An Airspace Planning Model for Selecting Flight-plans Under Workload, Safety, and Equity Considerations
Authors: Sherali Hanif D. , Cole Smith J. , Trani Antonio A.
Published: January 2003

In this paper, we present an airspace planning model (APM) that has been developed for use in both tactical and strategic planning contexts under various airspace scenarios. Given a set of flights for a particular time horizon, along with (possibly several) alternative flight-plans for each flight that are based on delays and diversions, due to special-use airspace (SUA) restrictions prompted by launches at spaceports or adverse weather conditions, this model prescribes a set of flight-plans to be implemented. The model formulation seeks to minimize and delay fuel-cost-based objective function, subject to the constraints that each flight is assigned one of the designated flight-plans, and that the resulting set of flight-plans satisfies certain specified workload, safety, and equity criteria. These requirements ensure that the workload for air-traffic controllers in each sector is held under a permissible limit, that any potential conflicts are routinely resolvable, and that the various airlines involved derive equitable levels of benefits from the overall implemented schedule. To solve the resulting 0–1 mixed-integer programming problem more effectively using commercial software (e.g., CPLEX-MIP), we explore the use of reformulation techniques designed to more closely approximate the convex hull of feasible solutions to the problem. We also prescribe a polynomial-time heuristic procedure that is demonstrated to provide solutions to the problem within 0.01% of optimality. Computational results are reported on several scenarios based on actual flight data obtained from the Federal Aviation Administration (FAA) to demonstrate the efficacy of the proposed approach for air-traffic management (ATM) purposes.
Origin-Based Algorithm for the Traffic Assignment Problem
Authors: Bar-Gera Hillel
Published: January 2003

We present an origin-based algorithm for the traffic assignment problem, which is similar conceptually to the algorithm proposed by Gallager and Bertsekas for routing in telecommunication networks. Apart from being origin-based, the algorithm is different from other algorithms used so far for the traffic assignment problem by its restriction to acyclic solutions and by the use of approach proportions as solution variables. Projected quasi-Newton search directions are used to shift flows effectively and to eliminate residual flows. Experimental results comparing the proposed algorithm with the state-of-the-practice algorithm of Frankand Wolfe demonstrate the algorithm's excellent convergence performance, especially when highly accurate solutions are needed. Reasonable memory requirements make this algorithm applicable to large-scale networks. The resulting solution has an immediate route flow interpretation, thus providing equivalent detail to route-based solutions.
A Stochastic Optimal Control Approach to Real-time, Incident-Responsive Traffic Signal Control at Isolated Intersections
Authors: Sheu Jiuh-Biing
Published: January 2003

Real-time, incident-responsive traffic control and management is vital to development of advanced incident management systems in ITS. More importantly, it provides, from an academic point of view, the linkages between incident detection, incident management, and traffic signal control. This study explores the application of a stochastic optimal control approach to real-time, incident-responsive traffic control at isolated intersections. In the methodology development, time-varying lane traffic state variables and control variables are specified to characterize sectionwide interlane and intralane traffic states under conditions of lane-blocking incidents. Following specification of system states, we formulated a discrete-time nonlinear stochastic model that comprises four types of equations, namely (1) recursive equations, (2) measurement equations, (3) incident-induced delay equations, and (4) boundary constraints. From the proposed stochastic model we then developed a stochastic optimal control algorithm to update the time-varying control variables and lane traffic state variables in real-time with lane-blocking incidents at isolated intersections. To generate traffic data used in model tests efficiently, we employed an advanced microscopic traffic simulator, Paramics, Version 3.0, which is developed to model and analyze ITS traffic flow conditions. The preliminary test results indicate that the proposed method can accomplish the goal of real-time, incident-responsive traffic signal control. In addition to proposing a new methodology, we hope that this study can initiate investigation into real-time, incident-responsive traffic control and management to achieve the final goal of networkwide incident-responsive, traffic-optimal control for incident management.
A Note on the Entropy Solutions of the Hydrodynamic Model of Traffic Flow
Authors: Velan Shane , Florian Michael
Published: January 2003

This paper describes the hydrodynamic model of traffic flow, which is used to derive the future density and flow along a roadway with known initial density. The complete model is a first-order partial differential equation, complemented by the entropy condition. The contributions from fluid dynamics and traffic flow theory are integrated. The entropy condition is proven to be equivalent to driver's ride impulse. It is shown that multiple weak solutions are possible for initial value problems with certain density discontinuities. In addition,the implications of nonsmooth equilibrium flow-density relationships are explored.
Validation of the Dutch version of the aggression questionnaire in adolescent male offenders
Authors: Morren Mattijn , Meesters Cor
Published: January 2003

This study examined the construct validity of the Dutch version of Buss and Perry’s Aggression Questionnaire (AQ) in 73 adolescent male offenders aged 12 to 18 years who were participating in a residential rehabilitation program. There was a strong positive association between the Hostility subscale of the AQ and psychological and physical symptoms. The nature of this connection was discussed. It was argued that the Hostility subscale measures some unique aspect of aggression that is not incorporated by the Physical Aggression, Verbal Aggression, or Anger subscales of the AQ. As expected, the AQ scales correlated significantly with trait anger, social desirability, and age. Furthermore, staff ratings of physical violence, verbal aggression, anger, and negative attitude were obtained for each subject. Correlations between the AQ scales and these ratings were low. Possible explanations for this unexpected finding are discussed. Finally, normative and internal structure data are presented. Aggr. Behav. 28:87–96, 2002. © 2002 Wiley‐Liss, Inc.
Reduction of dimensionality in choosing optimal control
Authors: Khazen Ellida M.
Published: January 2003

Given thatx(t) = (x1(t),…,xn(t)) represents a trajectory of the considered dynamical system, we demonstrate that reduction of dimensionality ofx(t) by using its principal components in choosing the optimal controlu(t) is necessary to overcome the computational difficulties that might arise in obtaining a solution of the optimal control problem. We obtain explicit solutions for linear time‐varying systems with quadratic cost functional and show how to overcome difficulties appearing in non‐linear matrix differential equations of Riccati type. A gradient method of searching for the close‐to‐optimal trajectory and control in non‐linear optimal control problems is also considered. Copyright © 2002 John Wiley & Sons, Ltd.
A new adaptive backstepping control algorithm for motion control systems — an implicit and symbolic computation approach
Authors: Yu Jen‐te , Chang Jie
Published: January 2003

A new adaptive integral backstepping control algorithm for motion control systems is proposed. The design approach is non‐conventional in that it only implicitly incorporates error states into a design Lyapunov function and computes time derivative of the Lyapunov function symbolically to the point of getting parameter estimate update laws on which desirable structures are imposed. The closed‐loop error system turns out to be linear and time‐varying and can be reformulated as a linear–non‐linear cascade system. Uniform exponential stability or absolute stability can be achieved. The design is robust against system parameter variations. The effectiveness and robustness of the control algorithm are verified by numerical examples. Copyright © 2002 John Wiley & Sons, Ltd.
Identification of a class of non‐linear parametrically varying models
Authors: Previdi F. , Lovera M.
Published: January 2003

The aim of this paper is to propose a novel class of non‐linear, possibly parameter‐varying models suitable for system identification purposes. These models are given in the form of a linear fractional transformation (LFT) where the ‘forward’ part is represented by a conventional linear regression and the ‘feedback’ part is given by a non‐linear dynamic map parameterized by a neural network (NN) which can take into account scheduling variables available for measurement.

For this specific model structure a parameter estimation procedure has been set up, which turns out to be particularly efficient from the computational point of view. Also, it is possible to establish a connection between this model class and the well known class of local model networks (LMNs): this aspect is investigated in the paper. Finally, we have applied the proposed identification procedure to the problem of determining accurate non‐linear models for knee joint dynamics in paraplegic patients, within the framework of a functional electrical stimulation (FES) rehabilitation engineering project. Copyright © 2002 John Wiley & Sons, Ltd.
Bayesian estimation of traffic lane state
Authors: Nagy Ivan , Kárný Miroslav , Nedoma Petr , Voráčová Šárka
Published: January 2003

Modelling of large transportation systems requires a reliable description of its elements that can be easily adapted to the specific situation. This paper offers mixture model as a flexible candidate for modelling of such element. The mixture model describes particular and possibly very different states of a specific system by its individual components. A hierarchical model built on such elements can describe complexes of big city communications as well as railway or highway networks.

Bayesian paradigm is adopted for estimation of parameters and the actual component label of the mixture model as it serves well for the subsequent decision making. As a straightforward application of Bayesian method to mixture models leads to infeasible computations, an approximation is applied. For normal stochastic variations, the resulting estimation algorithm reduces to a simple recursive weighted least squares.

The elementary modelling is demonstrated on a model of traffic flow state in a single point of a roadway. The examples for simulated as well as real data show excellent properties of the suggested model. They represent much wider set of extensive tests made. Copyright © 2003 John Wiley & Sons, Ltd.
Lyapunov‐based backward‐horizon adaptive stabilization
Authors: Venugopal Ravinder , Rao Venkatesh G. , Bernstein Dennis S.
Published: January 2003

In this paper we develop a discrete‐time adaptive stabilization algorithm based on a one‐step backward‐horizon cost criterion. By optimizing the cost with respect to the update step size, we obtain a gain update law that guarantees convergence of the plant states. The convergence proof is based on a modified Lyapunov technique. We extend the algorithm to include integral control for rejecting constant disturbances and we present an experimental application to DC motor positioning system. Copyright © 2003 John Wiley & Sons, Ltd.
Selective Hydrogenation for Fine Chemicals: Recent Trends and New Developments
Authors: Blaser Hans‐Ulrich , Malan Christophe , Pugin Benoît , Spindler Felix , Steiner Heinz , Studer Martin
Published: January 2003

In this overview, recent trends and developments for the selective hydrogenation of multifunctional molecules are discussed and assessed from the point of view of fine chemicals synthesis. In a first part, the design and preparation of catalysts and ligands with interesting properties are summarized, particularly meant for the catalysis specialist. The following topics are described in some detail: How enantioselective homogeneous catalysts are designed and tested; new effective chiral monodentate phosphines; successful bidentate phosphines ligand families (with axially chiral biaryl‐ and ferrocenyl‐based backbones, new phospholanes and with stereogenic phosphorus); novel bidentate ligand families with P‐O and P‐N bonds; and oxazoline‐based ligands. A short overview on immobilized chiral complexes and of the toolbox of heterogeneous catalysis (bimetallic, colloidal and modified catalysts) concludes this chapter. In a second part, progress for selected catalytic transformations and generic selectivity problems is described, intended mainly for the organic chemist who has to solve specific synthetic problems. Emphasis is on the following topics: The enantioselective hydrogenation of olefins with various substitution patterns; the chemo‐ and enantioselective hydrogenation of ketones; the diastereo‐ and enantioselective hydrogenation of CN functions; the stereoselective hydrogenation of aromatic rings; chemoselectivity and hydroxylamine accumulation in the reduction of functionalized nitroarenes; chemoselectivity and new protecting groups for catalytic debenzylation; the mild hydrogenation of carboxylic acid derivatives; and the chemoselective hydrogenation of nitriles. In the last parts of the review, transfer hydrogenation and mechanistic issues are discussed, followed by a short conclusions and outlook paragraph.
Towards a Large‐Scale Asymmetric Reduction Process with Isolated Enzymes: Expression of an (S)‐Alcohol Dehydrogenase in E. coli and Studies on the Synthetic Potential of this Biocatalyst
Authors: Hummel Werner , Abokitse Kofi , Drauz Karlheinz , Rollmann Claudia , Gröger Harald
Published: January 2003

An NAD‐dependent and widely applicable (S)‐alcohol dehydrogenase is isolated and described as a novel enzyme. It is expressed in an E. coli strain with a high production potential. The application of this enzyme in asymmetric biocatalytic reduction is presented as well. This enzyme shows a broad substrate range comprising aliphatic and aromatic ketones as well as β‐keto esters. The synthetic application of this new (S)‐alcohol dehydrogenase led to optically active alcohols in high conversion rates accompanied by enantioselectivities of up to >99% ee. Compared to the wild‐type enzyme significant advantages are observed besides the improved availability, such as a high enantioselectivity independent of the reaction time. Furthermore, the alcohol dehydrogenase was cloned and successfully overexpressed in E. coli resulting in a biocatalyst with a potential to be available on technical scale in the future. The development of a large‐scale available and widely applicable (S)‐alcohol dehydrogenase is one prerequisite to use isolated enzymes for asymmetric reduction processes as a valuable tool.
Asymmetric Catalysis: Science and Opportunities (Nobel Lecture 2001)
Authors: Noyori Ryoji
Published: January 2003

Asymmetric catalysis, in its infancy in the 1960s, has dramatically changed the procedures of chemical synthesis, and resulted in an impressive progression to a level that technically approximates or sometimes even exceeds that of natural biological processes. The recent exceptional advances in this area attest to a range of conceptual breakthroughs in chemical sciences in general, and to the practical benefits of organic synthesis, not only in laboratories but also in industry. The growth of this core technology has given rise to enormous economic potential in the manufacture of pharmaceuticals, animal health products, agrochemicals, fungicides, pheromones, flavors, and fragrances. Practical asymmetric catalysis is of growing importance to a sustainable modern society, in which environmental protection is of increasing concern. This subject is an essential component of molecular science and technology in the 21st century. Most importantly, recent progress has spurred various interdisciplinary research efforts directed toward the creation of molecularly engineered novel functions. The origin and progress of my research in this field are discussed.
A Novel Class of Ferrocenyl‐Aryl‐Based Diphosphine Ligands for Rh‐ and Ru‐Catalysed Enantioselective Hydrogenation
Authors: Sturm Thomas , Weissensteiner Walter , Spindler Felix
Published: January 2003

A series of diphosphines of the novel Walphos ligand family all based on a phenylferrocenylethyl backbone were synthesised in a four‐step sequence. In the rhodium‐ or ruthenium‐catalysed asymmetric hydrogenation of olefins and ketones enantioselectivities of up to 95% and 97%, respectively, were obtained. A 2‐isopropylcinnamic acid derivative of industrial interest was hydrogenated in 95% ee and with turnover numbers of >5000.
Synthesis of Chiral Trifluoromethylated Amines by Palladium‐Catalyzed Diastereoselective Hydrogenation‐Hydrogenolysis Approach
Authors: Török Béla , Surya Prakash G. K.
Published: January 2003

The synthesis of chiral 2,2,2‐trifluoro‐1‐phenylethylamines by palladium‐catalyzed diastereoselective heterogeneous catalytic hydrogenation is described. The one‐pot process involves two steps; the diastereoselective hydrogenation of chiral 2,2,2‐trifluoro‐1‐phenylethyl‐N‐1′‐phenylethylimines and the hydrogenolysis of the methylbenzyl group on the amino function. During both the hydrogenation and hydrogenolysis steps favorable stereoinduction was observed, and the products were obtained in 90–93% ee and 50–55% yield.
Iridium‐Catalyzed Enantioselective Hydrogenation of Imines with Xylose Diphosphite and Diphosphinite Ligands
Authors: Guiu Ester , Muñoz Bianca , Castillón Sergio , Claver Carmen
Published: January 2003

Iridium complexes incorporating xylose diphosphinite 1 and diphosphite 2, 3 ligands as source of chirality are active catalysts for the hydrogenation of imines providing moderate ee. The enantioselectivity depends on the fine tuning of the structural parameters of the ligand and on the effect of additives.
Dramatic Pressure Effects on the Selectivity of the Aqueous/Organic Biphasic Hydrogenation of trans‐Cinnamaldehyde Catalyzed by Water‐Soluble Ru(II)‐Tertiary Phosphane Complexes
Authors: Papp Gábor , Elek János , Nádasdi Levente , Laurenczy Gábor , Joó Ferenc
Published: January 2003

In a water/chlorobenzene biphasic reaction, the hydrogenation of trans‐cinnamaldehyde, catalyzed by water‐soluble Ru(II)‐phosphane complexes at pH 3.04 (phosphate buffer), produces a 61:39 mixture of cinnamyl alcohol and dihydrocinnamaldehyde at 1 bar H2; however, the selectivity is increased to 93:7 by increasing the hydrogen pressure to 8 bar.
Amphiphilic Resin‐Supported Ruthenium(II) Complexes as Recyclable Catalysts for the Hydrogenation of Supercritical Carbon Dioxide
Authors: Kayaki Yoshihito , Shimokawatoko Yoshiki , Ikariya Takao
Published: January 2003

Dichloro‐ and dihydridoruthenium(II) catalysts attached to an amphiphilic resin (PS−PEG) were prepared and tested for hydrogenation of supercritical carbon dioxide (scCO2) in the presence of dimethylamine leading to N,N‐dimethylformamide (DMF). The supported catalysts were successfully recyclable with only moderate loss of activity.
Synthesis and Application of Chiral Phospholane Ligands Bearing a Sterically and Electrically Adjustable Moiety
Authors: Matsumura Kazuhiko , Shimizu Hideo , Saito Takao , Kumobayashi Hidenori
Published: January 2003

A series of C1‐symmetric phosphine‐phospholane ligands, 1‐(disubstituted phosphino)‐2‐(phospholano)benzenes (5), which are called UCAPs, with an achiral phosphino group and a chiral phospholane which can be sterically and electrically adjustable, has been designed and synthesized. In the asymmetric hydrogenation of (Z)‐N‐benzoyl‐1‐phenylpropenamine (3), the stereorecognition abilities of the 5d−e–Rh catalysts which have a bulkier aryl substituent on the achiral phosphorus are superior to that observed with the DuPHOS‐Rh catalyst. The effects of varying substituents on the achiral phosphorus atom are discussed.
Synthesis of Novel Chiral Benzophospholanes and Their Application in Asymmetric Hydrogenation
Authors: Shimizu Hideo , Saito Takao , Kumobayashi Hidenori
Published: January 2003

A new class of chiral ligands bearing one or two benzophospholanes was developed for the purpose of Ru‐catalyzed asymmetric hydrogenation. Although results of the Ru catalysis remain insufficient so far, 1,2‐bis(2‐isopropyl‐2,3‐dihydro‐1H‐phosphindol‐1‐yl)benzene (iPr‐BeePHOS: 2b) has been found to provide high enantioselectivity in the Rh‐catalyzed asymmetric hydrogenation of an enamide.
High Throughput Kinetic Investigations of Asymmetric Hydrogenations with Microdevices
Authors: de Bellefon C. , Pestre N. , Lamouille T. , Grenouillet P. , Hessel V.
Published: January 2003

A high throughput test which is based on a micromachined mixer for molecular gas‐liquid reactions was evaluated for the kinetic investigation of the asymmetric hydrogenation of methyl Z‐(α)‐acetamidocinamate with a rhodium/(S,S‐BDPPTS) catalyst in an aqueous phase. Up to 214 tests were performed in a short time and with an average inventory of Rh/test as low as 14 μg. Comparisons with traditional batch experiments are provided.
Enantioselective Hydrogenation of Imines Using a Diverse Library of Ruthenium Dichloride(diphosphine)(diamine) Precatalysts
Authors: Cobley Christopher J. , Henschke Julian P.
Published: January 2003

A range of aromatic and cyclic imines were subjected to asymmetric hydrogenation with catalysts derived from complexes of the type RuCl2(diphosphine)(diamine). Good to high enantioselectivities were observed. For each imine, a library of chiral complexes based on different diphosphine and diamine combinations was screened. A different combination of diphosphine and diamine was required each time to obtain the optimum enantioselectivity.
Catalyst Encapsulation and Substrate Solubilization in Polymer‐Surfactant Complexes and Their Use in a Membrane Reactor
Authors: Fuhrmann Hans , Dwars Torsten , Michalik Dirk , Holzhüter Gerd , Grüttner Cordula , Kragl Udo , Oehme Günther
Published: January 2003

A chiral non‐racemic Rh complex was entrapped in a number of charged polymer‐surfactant complexes (PSCs) and used as micellar‐enlarged catalyst for the enantioselective hydrogenation of an α‐amino acid precursor in a membrane reactor. The retention behavior of different ultrafiltration membranes in dependence on the chemical nature and the molar mass of the PSCs as well as the loading behavior of the system were investigated. The chiral hydrogenation product was obtained with good enantioselectivity and space‐time yield. A lowering of the activity of the multiply used catalyst was caused mainly by a blockage of the PSC and not by the decomposition and leaching of the encapsulated catalyst. TEM images before and after the solubilization of the catalytic system support the view that a PSC with a loose, gel‐like structure and incorporated micelles yields the best results in the repetitive batch process.
Minor Modifications to the Ligands Surrounding a Ruthenium Complex Lead to Major Differences in the Way in which they Catalyse the Hydrogenation of Arenes
Authors: Dyson Paul J. , Ellis David J. , Laurenczy Gábor
Published: January 2003

The hydrogenation of benzene and other arenes under aqueous‐organic biphasic conditions is evaluated using the ruthenium complexes Ru(η6‐C10H14)(pta)Cl2 (pta=1,3,5‐triaza‐7‐phosphaadamantane), Ru(η6‐C10H14)(tppts)Cl2 (tppts=tris‐3‐sulfonatophenylphosphine trisodium salt) and [Ru(η6‐C10H14)(pta)2Cl]+. The active catalysts formed during the hydrogenations correspond to a trinuclear cluster, a colloid and a mononuclear complex, respectively.
A Comparison of Ruthenium‐Catalysed Arene Hydrogenation Reactions in Water and 1‐Alkyl‐3‐methylimidazolium Tetrafluoroborate Ionic Liquids
Authors: Dyson Paul J. , Ellis David J. , Henderson William , Laurenczy Gábor
Published: January 2003

The hydrogenation of benzene and other arene substrates under biphasic conditions is evaluated using the catalyst precursor Ru(η6‐C10H14)(pta)Cl2 (pta=1,3,5‐triaza‐7‐phosphaadamantane) immobilised in water and 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids. The effect that contamination of the 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids with chloride has on the hydrogenation reaction has also been examined. Of the immobilisation solvents tested the optimum solvent was found to be chloride‐free 1‐butyl‐3‐methylimidazolium tetrafluoroborate. Catalytic turnovers in this solvent are highest, and in general, turnovers for the hydrogenation reactions follow the trend: chloride‐free 1‐butyl‐3‐methylimidazolium tetrafluoroborate > water > chloride‐contaminated 1‐butyl‐3‐methylimidazolium tetrafluoroborate.
Arene Hydrogenation with a Stabilised Aqueous Rhodium(0) Suspension: A Major Effect of the Surfactant Counter‐Anion
Authors: Roucoux Alain , Schulz Jürgen , Patin Henri
Published: January 2003

A reduced aqueous colloidal suspension of rhodium shows an efficient activity in the catalytic hydrogenation of various benzene derivatives under biphasic conditions at room temperature and under atmospheric hydrogen pressure. The rhodium nanoparticles in the size range of 2–2.5 nm have been synthesised by reducing RhCl3⋅3 H2O with sodium borohydride and were stabilised by highly water‐soluble N,N‐dimethyl‐N‐cetyl‐N‐(2‐hydroxyethyl)ammonium salts (HEA16X, X=Br, Cl, I, CH3SO3, BF4). The major influence of the counter‐ion of these surfactants on catalytic activity and recycling is described. The best results have been obtained with chloride ammonium salts HEA16Cl.
Ruthenium‐Catalysed Enantioselective Hydrogenation of Trisubstituted Enamides Derived from 2‐Tetralone and 3‐Chromanone: Influence of Substitution on the Amide Arm and the Aromatic Ring
Authors: Renaud J. L. , Dupau P. , Hay A.‐E. , Guingouain M. , Dixneuf P. H. , Bruneau C.
Published: January 2003

Cyclic enamides were prepared in one step from tetralone and chromanone derivatives and primary amides under acidic conditions. The enantioselective hydrogenation of these enamides bearing an endocyclic trisubstituted carbon‐carbon double bond was performed at room temperature in the presence of ruthenium catalysts. On the one hand, the nature of the amide group had little influence on the enantioselectivity of the hydrogenation when mononuclear precatalysts were used. On the other hand, the presence of a coordinating atom at some specific position on the tetralone and chromanone skeleton led to a dramatic decrease of the enantiomeric excesses.
Asymmetric Cleavage of Racemic 1,3‐Oxazolidines – A New Dynamic Process in Homogeneous Rh(I)‐Catalyzed Hydrogenation
Authors: Tararov Vitali I. , Kadyrov Renat , Monsees Axel , Riermeier Thomas H. , Börner Armin
Published: January 2003

The mechanism of the homogeneously catalyzed hydrogenation of 1,3‐oxazolidines with a Rh(I) diphosphane catalyst affording tertiary hydroxyethyl‐substituted amines was investigated with the help of D2 labelling experiments. It was found that the reaction proceeds via prochiral intermediates with, preferentially, an iminium cation being in equilibrium with the 1,3‐oxazolidine. This observation opened up the opportunity to run the reaction stereoselectively by employment of a racemic 1,3‐oxazolidine and a chiral catalyst. By means of high‐throughput screening considering 144 catalysts a cationic Rh(NORPHOS)‐complex was identified as the most efficient catalyst, which afforded after optimization of solvent, temperature and H2 pressure the corresponding chiral hydroxyethylamine in 95% yield and 80% ee.
Asymmetric Activation/Deactivation of Racemic Ru Catalysts for Highly Enantioselective Hydrogenation Irrespective of Ketonic Substrates: Molecular Design of Dimethylbinaphthylamine for Enantiomeric Catalysts Discrimination
Authors: Mikami Koichi , Korenaga Toshinobu , Yusa Yukinori , Yamanaka Masahiro
Published: January 2003

Asymmetric activation and deactivation of racemic catalysts are two extremes in asymmetric catalysis. In a combination of these two protocols, higher enantioselectivity can be achieved by maximizing the difference in catalytic activity between the enantiomers of racemic catalysts through selective activation and deactivation of enantiomeric catalysts. 3,3′‐Dimethyl‐2,2′‐diamino‐1,1′‐binaphthyl (DM‐DABN) is thus designed as a chiral poison (deactivator) for complete enantiomer resolution of racemic BINAP‐Ru(II) catalysts. The catalyst system of DM‐DABN, 1,2‐diphenylethylenediamine (DPEN), and racemic BINAP‐Ru(II) led to great success in highly enantioselective hydrogenation irrespective of the ketonic substrates. The lower catalytic activity of the BINAP‐Ru(II)/DM‐DABN complex stems from the electron delocalization from the Ru center to the diamine moiety in contrast to the BINAP‐Ru(II)/DPEN complex where the highest electron densities are localized on the Ru‐N region. The present ‘asymmetric activation/deactivation protocol' can provide a guiding principle for the rational design of a molecule for enantiomeric discrimination between racemic catalysts.