Studies of intramolecular tethered Diels-Alder reactions
File(s)
Author(s)
Ainsworth., Peter James
Type
Thesis
Abstract
This thesis is divided into three chapters. The first chapter is a review of the intramolecular Diels-Alder reaction in the synthesis of medium and large rings. The review focuses on the literature to date that has demonstrated the use of the IMDA reaction to form both medium and large rings in a regio- and stereoselective fashion. The second chapter is a discussion of the results obtained during research into tethered IMDA reactions. It is divided into three sections: the first section describes the synthesis of a series of benzylidene and isopropylidene ether tethered trienes and their subsequent cyclisation under thermal conditions. The cyclisation of the benzylidene ether tethered trienes was also investigated under Lewis acid-catalysed conditions. The effect of substitution of the dienophile on the cyclisation reaction was investigated by the synthesis of trienes bearing methyl substituents on the alkene and at the allylic position. Attempts to achieve asymmetric IMDA reactions are also described by the use of chiral cyclohexyl derived trienes. Cleavage of the unsymmetrical ether cycloadducts from these cyclisations with high degrees of regioselectivity is also described. The second section investigates the effect of substitution at the 3-position of the diene in silyl acetal tethered trienes. Cyclisation of an unsubstituted triene yielded exclusively the cis-fused bicyclo[5.4.0] system. Introduction of a methyl substituent at the 3-position of the diene, however, yielded a 1: 1 mixture of the trans- and cis-fused bicyclo[5.4.0] systems. The third, and final section, investigates the carbon acetal as a potential tether for use in the IMDA reaction and the effect this new linking group has on the selectivity of the cyclisations.. The synthesis of mixed acetals is described under both acidic and non-acidic conditions and the resulting series of trienes were cyclised under thermal conditions. The removal of the carbon acetal tether from the cycloadduct was also achieved readily. An attempt has been made to explain the stereochemical outcome of each cyclisation reaction by reference to transition state models. Chapter 3 of this thesis is the experimental section, which gives a detailed description of the synthesis and physical properties of the molecules discussed in Chapter 2.
Version
Open Access
Date Awarded
1995
Advisor
Craig, Dr. Donald
Sponsor
SERC
Publisher Department
Department of Chemistry
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)