9,078 research outputs found
The generation and reactivity of functionalised organozinc carbenoids for cyclopropane synthesis
This thesis describes the generation and reactivity of functionalised organozinc
carbenoids for cyclopropane synthesis with alkenes.
In the introductory chapter, a brief overview of the different methods for preparation of
heteroatom-functionalised cyclopropanes is presented, including [2+1] cycloaddition
reactions using a carbene or carbenoid as a cyclopropanating agent with an alkene, ionic
stepwise methods, and chemical modifications from existing cyclopropanes. The
remainder of this chapter then focuses on previous work within our own group in this
area.
The second chapter presents the results obtained from different areas of research in the
present study, the first of these being a deeper understanding and extension of the
research work undertaken by my predecessor for the development of the
cyclopropanation reaction using an âamidoorganozincâ carbenoid derived from N,N
diethoxymethyloxazolidinones derivatives in the presence of a source of zinc and
chlorotrimethylsilane. Thus, the chemoselectivity and stereoselectivtity of the reaction
were fully studied, and a quadrant model was constructed to rationalise the
stereochemistry of the products obtained. The second part of this section outlines the
generation of new enantiopure organozinc carbenoids precursors derived from
substituted chiral precursors followed by the synthesis of novel enantiopure highly
functionalised N-cyclopropyl oxazolidinones. The intramolecular version of this
cyclopropanation reaction was then successfully studied using diethoxylactam
derivatives as organozinc carbenoid precursors. The methodology was then applied to
the preparation of novel aminocyclopropyl functionalised compounds selected as
interesting building blocks which can lead to the synthesis of natural and biologically
active compounds. The fifth part of this chapter describes subsequent studies towards
the design of new carbenoid precursors containing additional functional groups of
interest. Finally, a brief study on the potential of an organozinc carbenoid to participate
in a novel [2,3] sigmatropic rearrangement was investigated.
The thesis concludes with a summary of the results obtained, a detailed description of
the experimental procedures used and the characterization and analysis of the
compounds prepared, together with a full bibliography
A Tale of Two Debt Crises: A Stochastic Optimal Control Analysis
Banks should evaluate whether a borrower is likely to default. I apply several techniques in the extensive mathematical literature of stochastic optimal control/dynamic programming to derive an optimal debt in an environment where there are risks on both the asset and liabilities sides. The vulnerability of the borrowing firm to shocks from either the return to capital, the interest rate or capital gain, increases in proportion to the difference between the Actual and Optimal debt ratio, called the excess debt. As the debt ratio exceeds the optimum, default becomes ever more likely. This paper is âA Tale of Two Crisesâ because the analysis is applied to the agricultural debt crisis of the 1980s and to the sub-prime mortgage crisis of 2007. A measure of excess debt is derived, and we show that it is an early warning signal of a crisis.optimization, banking, stochastic optimal control, agriculture debt crisis, subprime mortgage crisis
The Diversity of Debt Crises in Europe
The foreign debts of the European countries are at the core of the current crises. Generally, the crises are attributed to government budget deficits in excess of the values stated in the Stability and Growth Pact (SGP)/Maastricht treaty. Proposals for reform generally involve increasing the powers of the European Union to monitor fiscal policies of the national governments and increasing bank regulation. My article is concerned with the following issues. [Q1] How can one explain the inter country differences in the debt crisis in Europe? Is there a single explanation, cause? [Q2] Specifically, were the crises due to government budget deficits or to the private sector? The answer will determine what is the appropriate policy to prevent a recurrence. [Q3] The Stability and Growth Pact/Maastricht Treaty and the European Union focused upon rules concerning government debt ratios and deficit ratios. They ignored the problem of âexcessiveâ debt ratios in the private sector that led to a crisis in the financial markets. Neither the markets nor the Central Banks anticipated the crises until it was too late. My basic questions are: What is an âexcessiveâ private sector debt ratio that is likely to lead to a crisis? What are theoretically based, not empirical ad hoc, Early Warning Signals (EWS) of debt crises? The answers determine to a large extent how one should evaluate proposals for economic reform, to avert future crises?European debt crisis, excess debt, early warning signals, domestic housing sector, government deficit debt
A Critique of the Literature on the US Financial Debt Crisis
A healthy financial system encourages the efficient allocation of capital and risk. The collapse of the house price bubble led to the financial crisis that started in 2007. There is a large empirical literature concerning the relation between asset price bubbles and financial crises. I evaluate the key studies with the respect to the following questions. To what extent do the empirical relations in the existing literature help to identify asset price bubbles ex-ante or ex-post? Do the empirical studies have theoretical foundations? On the basis of that critique, I explain why the application of stochastic optimal control (SOC)/dynamic risk management is a much more effective approach to determine the optimal degree of leverage, the optimum and excessive risk and the probability of a debt crisis. The theoretically founded early warning signals of a crisis are shown to be superior, in general, to those empirical relations in the literature. Moreover the SOC analysis provides a theoretical explanation of the extent that the empirical measures in the literature can be useful.stochastic optimal control, mortgage and financial crises, Ito equation, optimal dynamic risk management, warning signals of crisis, optimal leverage and debt ratios, Congressional Oversight Panel, Case-Shiller index
Application of Stochastic Optimal Control to Financial Market Debt Crises
This interdisciplinary paper explains how mathematical techniques of stochastic optimal control can be applied to the recent subprime mortgage crisis. Why did the financial markets fail to anticipate the recent debt crisis, despite the large literature in mathematical finance concerning optimal portfolio allocation and stopping rules? The uncertainty concerns the capital gain, the return on capital and the interest rate. An optimal debt ratio is derived where the drift is probabilistic but subject to economic constraints. The crises occurred because the market neglected to consider pertinent economic constraints in the dynamic stochastic optimization. The first constraint is that the firm should not be viewed in isolation. The optimizer should be the entire industry. The second economic constraint concerns the modeling of the drift of the price of the asset. The vulnerability of the borrowing firm to shocks from the capital gain, the return to capital or the interest rate, does not depend upon the actual debt/net worth per se. Instead it increases in proportion to the difference between the Actual and Optimal debt ratio, called the excess debt. A general measure of excess debt is derived and I show that it is an early warning signal of the recent crisis.stochastic optimal control, dynamic optimization, mortgage crisis, Ito equation, risk aversion, debt management, warning signals
Stochastic Optimal Control Modeling of Debt Crises
What is an optimal or a sustainable external debt - for a country, region or sector? How should one monitor and evaluate debt to preclude a crisis? We use stochastic optimal control/dynamic programming to derive an optimal debt. The deviation of the actual from the optimal will serve as a Warning Signal of a crisis. There is a correspondence between Hamilton-Jacobi-Bellman equation of Dynamic Programming and the static Mean-Variance (M-V) analysis in finance. A graphic analysis of M-V is helpful to explain the implications of DP. An explicit example is the US Agricultural debt crisis.stochastic optimal control, debt, international finance, US agricultural crisis, Mean-Variance analysis, Hamilton-Jacobi-Bellaman equation
Greenspan, Dodd-Frank and Stochastic Optimal Control
Finanzmarkt; Regulierung; Zentralbank; Kontrolltheorie; USA
Interpreting children's rights education: three perspectives and three roles for teachers
In this article I argue that the world-view adopted by Childrenâs Rights Education (CRE) advocates influences the form of education they present. In the first part of the article I discuss three perspectives: (1) the legalistic perspective, which sees CRE as a matter of technical implementation; (2) the reformist-hermeneutic perspective, which focuses on the interpretation and elaboration of core childrenâs rights texts; and (3) the radical view, which sees CRE as part of a broader political struggle for education. In the second part I consider the implications of each of these perspectives for teachers and argue that only the latter tradition positions teachers as agents of change, whilst the others reduce teacher agency. The article argues that the first two perspectives are unlikely to achieve radical change for children, and that CRE advocates must engage more overtly with the politically contested nature of education
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