| dc.description.abstract | Routes to novel heterocyclic azo compounds and components of use as potential
inkjet dyes were investigated.
A new route to fluorenones from biphenyl acid chlorides using FVP (Flash
Vacuum Pyrolysis) has been discovered. Fluorenone and 4-methylfluoren-9-one were
prepared by FVP of 2-phenylbenzoyl chloride and 2-methylbiphenyl-2-carbonyl
chloride respectively. Xanthen-9-one and thioxanthen-9-one were also prepared by
FVP from the corresponding acid chlorides.
9-Phenanthrol could also be prepared via the FVP of biphenylacetyl choride
and the application of this method to a heterocylic thiophene system afforded
naphtho[1,2-b]thiophen-4-ol. Naphtho[2,1-b]thiophen-4-ol and naphtho[1,2-b]furan-
4-ol could be obtained in low yields by the FVP of (2-thiophen-3-ylphenyl)acetic acid
methyl ester and (2-furan-2-ylphenyl) acetic acid methyl ester over a tungsten trioxide
catalyst. Coupling of these systems with the diazonium salt of Acid Yellow 9 afforded
the corresponding azo compounds.
New heterocyclic dyes were also prepared from the condensation of
heterocyclic hydrazines with 4,9-disulfophenanthrenequinone. Pyridine, pyridazine,
phthalazine, isoquinoline and 2-quinoline disulfophenanthrene quinone metallised 2:1
nickel complexed magenta dyes were prepared. Industrial tests by standard methods
revealed the pyridazine dye has a particularly impressive balance of light and ozone
fastness over similar magenta dyes.
The reaction of an arylnitro compound with 2-aminopyridine appeared to be
an attractive and high yielding route to 2-(phenylazo)pyridine. However, application
of this reaction to substituted and naphthalene systems failed. This afforded byproducts
due to nucleophilic substitution of groups such as methoxy and the relatively
uncommon nucleophilic substitution of hydrogen with none of the required azo
products obtained. Therefore it appeared that the reaction of a nitro and amine was not
a robust and versatile route to heterocyclic azo compounds.
An alternate route to heterocyclic azo compounds involved the use of the Mills
reaction by the condensation o-anisidine, p-chloroaniline, 2-aminophenol, 3-
aminophenol, naphthylamine, 8-amnioquinoline and 2-acetylamino-5-aminobenzenesulfonic
acid with 2-nitrosopyridine afforded the heterocyclic azo products in
moderate to high yields. The Mills reaction does appear to be the favored route to
heterocyclic azo compounds. Several factors were identified which affect the process of bisazo coupling of
chromotropic acid and products obtained. Reaction at the ipso position of
monoPACAs (2-phenylazochromotropic acid) leading to increased yields of the ipso
substitution monoPACA by-product as opposed to the expected bisazo coupling
position was a major problem. Studies indicated reactivity at the ipso position was
greatly reduced by the presence of electron withdrawing groups around the phenyl
ring of the monoPACA.
Further study indicated reaction at the bisazo coupling position increased with
the strength of the diazonium salt used in bisazo coupling. Therefore the electronic
nature of the monoPACA starting material and the diazonium salt used in bisazo
coupling greatly affected the products obtained.
Reaction pH studies also revealed attack at the bisazo coupling position
increases with pH and at lower pH (5.0 – 8.0) attack at the ipso position dominated.
Reactivity of the monoPACA starting material also increased with pH.
The influence of steric effects upon bisazo coupling revealed, in the cases
where ortho sulfonic acid groups were present in the monoPACA, a reduction in
attack at the ipso position. Hence the reaction appeared to be directed towards the
required bisazo coupling position. | en |
