Pucci, Sabrina; (2004) Amidoalkylations and cyclisations involving hydroxamic acids and their derivatives. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Amidoalkylations are multicomponent reactions, which proceed via a highly reactive intermediate such as the N-acyliminium species. Amidoalkylations involving hydroxamic acids are rare and their reactivity in three-component condensations with carbonyl compounds is almost unknown. The development of new synthetic routes to both natural and novel cyclic hydroxamic acids is of primary importance in view of their potential in a wide range of biological applications. A new ring-closure reaction involving unsaturated hydroxamic acids has been investigated. In Chapter 1 is depicted a complete introduction to hydroxamic acids, including their biological and physical properties, structure and preparation. A variety of unsaturated and O-protected hydroxamic acids were prepared in order to test the scope of the three-component amidoalkylation condensation and the acid- catalysed cyclisation. In Chapter 2 is described a new amidoalkylation that furnishs acyclic aliphatic β-hydroxamic acids aldehydes for the first time. Unique features include: (a) in situ formation of the presumed imine substrate (from a hydroxamic acid and an aldehyde) (b) subsequent amidoalkylation by an aldehyde, in an overall one-pot process to give (c) an isolable β-hydroxamic acid aldehyde as the product. Chapter 3 describes attempts to generate heterocycles by treating unsaturated hydroxamic acids with trifluoromethanesulfonic acid (TfOH). At 30% concentration of TfOH this was largely successful. Chapter 4 describes attempts to broaden the scope of the multicomponent reactions and to uncover new cyclisations. Hydrazides were prepared in the hope that their enhanced nucleophilicity would assist in carbonyl condensations.

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