Summary
The aim of the work reported in this thesis is to develop methods suitable for the
synthesis of valuable industrial materials cleanly and efficiently. Solid reusable
heterogeneous catalysts such as zeolites, clays, and synclysts can play an important role
in improving such processes. The specific ultimate goal of the project is to achieve high
yields in regioselective substitution reactions of naphthalene. This topic is of great
interest as some 2,6-disubstituted naphthalenes can be oxidized to naphthalene-2,6dicarboxylic acid (NDCA), used to prepare the commercially valuable poly(ethylene
naphthalene-2,6-dicarboxylate) (PEN). However, no method has yet been found for
sufficiently selective 2,6-dimethylation (DMN) and this project therefore seeks to
discover other methods for the production of 2,6-disubstituted naphthalenes that can
eventually be converted into NDCA.
Chapter One
Chapter One describes the important role of heterogeneous solid catalysts. Zeolites and
clays have achieved importance for selectivity in organic syntheses since they offer
advantages in comparison with conventional homogeneous catalysts, such as being easily
recovered by filtration and being used several times before losing their selectivities.
Chapter Two
Chapter Two describes a literature survey for the electrophilic substitution reactions of
naphthalene. Syntheses of various substituted and polysubstituted naphthalenes have been
reported. In particular, direct alkylation, acylation and bromination reactions are
discussed.
Chapter Three
Chapter Three describes a convenient method for the synthesis of 2,6dialkylnaphthalenes selectively in high yields (70%) with no 2,7-isomers detected, by
autoclave reaction of tertsufficient H-Mordenite zeolite after multistaging the reaction. The 2,6dialkylnaphthalenes formed include 2,6-di-tert-amylnaphthalene (mainly) and 2-tertamyl-6-tert-butylnaphthalene. The former could in principle be cracked to give DMN, a
key intermediate in the production of PEN.
Chapter Four
Chapter Four describes the catalytic power and high activity of zeolites, synclysts, and
calcined montmorillonite KSF clay in direct bromination of naphthalene with bromine.
The use of catalyst leads to reduction of the energy barrier for the direct bromination
reactions of naphthalene. These methods of synthesis of polybrominated naphthalenes
have several advantages and sometimes great novelty. This work revealed that selectivity
and reactivity can be controlled and changed by manipulating the mole equivalents of
bromine, the reaction time, the amount and type of catalyst. In general, regioselective
bromination of naphthalene was efficiently achieved. Efficient and novel syntheses were
described for 1,4-di, 1,5-di, 1,4,6-tri, 1,3,5,7-tetra and the new 1,2,4,6-tetrabromonaphthalenes.
Chapter Five
Chapter Five describes debromination of a mixture of tetrabromonaphthalenes (TBNs)
in an attempt to produce 2,6-dibromonaphthalene. The method was successful and has
been achieved via selective bromine-lithium exchange of bromo substituents at αpositions. The synthesis of 2,6-dibromonaphtalene (2,6-DBN) via the method reported
has several advantages and great novelty, and the 2,6-DBN can be considered as a
starting point for the formation of other 2,6-functionalised naphthalenes.