Acylative cleavage of some cyclic ethers and study of a novel potassium complex

Abstract

Chapter 1 describes ring-opening reactions of cyclic ethers that are described in the literature. The extensive work carried out on tetrahydrofuran is discussed, but it is noted that reactions involving 2,5-dihydrofuran have been significantly less explored. The importance of 7 oxabicyclo[2.2.1]heptanes and their derivatives in natural product synthesis is highlighted, with emphasis on the different methods employed to break the ether bond. The different types of ion complexing ethers are discussed, as is a reported synthesis of a podate potassium complex, which it is intended to further explore. Chapter 2 discusses the attempted ring-opening reactions of 7-oxabicyclo[2.2.1]heptenes by their reactions with mixed carboxylic-trifluoroacetic anhydrides. The chapter includes a description of modifications to the original system and of repeated attempts at ring-opening. Some other bicyclic ring systems are also discussed. Chapter 3 describes the Lewis acid-catalysed ring-opening reactions of 2,5-dihydrofuran and acyl chlorides to give 1-acyloxy-4-chlorobut-2-enes where the olefmic geometry of 2,5-dihydrofiiran is retained. The preparation of aryl, alkyl and unsaturated esters is reported. The general reactivity of the resulting compounds is investigated, including the reactivity of the chlorine substituent towards a range of nucleophiles. An intramolecular Heck reaction is attempted and a proposed synthesis of a four membered sugar is discussed. Chapter 4 reports that the reaction of tetrahydrofuran with mixed carboxylic -trifluoroacetic anhydrides in the presence of iodide ion gives 1-acyloxy-4-iodobutanes. The preparation of aryl, alkyl and unsaturated esters is described. The methodology is also applied to a precursor of the drug Mebeverine that leads to a shorter and more efficient synthesis of this pharmaceutical. Chapter 5 describes the synthesis of a previously proposed potassium complex from a triol derived from geranyl acetate. Another method of complex synthesis is described involving alkali metal silanolates. The attempted synthesis of a borate complex is also discussed.