Aspects of the preparation and properties of some conformationally biased dihydroaromatic compounds

Abstract

The work described in this thesis is concerned with preparation and conformation of dihydroaromatic molecules. In part I the use of alkaline metal/liquid ammonia solutions in the preparation of dihydroaromatic compounds is reviewed; particular emphasis being placed on the effect of the substituent on the nature of the products obtained. The reduction of several benzoic acid and naphthoic acid derivatives has been investigated with a view to using the alkaline metal/liquid ammonia sequence to prepare sterically hindered dihydrobenzoic acids and dihydronaphthoic acids. 1,4-Dihydro-8-methyl -l-naphthoic acid and 1,4-dihydro-8-isopropyl-l-naphthoic acid have been successfully prepared by this method. In the course of this work the reduction of the lactones phthalide and naphthalide and their dimethyl analogues have been studied. In these cases, there is competition between reduction of the aromatic ring and of the ester formation. Factors which influence the competition between these two reaction pathways have been investigated. In Part II evidence for the conformations of dihydro-aromatic rings is reviewed and the effect of the substituents is discussed. Nuclear magnetic resonance (nmr) spectroscopic data for dihydroaromatic compounds prepared in Part I are analysed in detail; these data are then used to determine the conformations of these conformationally biased and conformationally locked dihydroaromatic rings.