Various attempts have been made to synthesise 1:11 - disubstituted benzanthrones and some interesting results
have been obtained. In an attempted synthesis of the
nitrile of benzanthronylglyoxyiic acid by the standard
method of treating the acid chloride of 11- carboxybenzanthrone with hydrogen cyanide and pyridine the hithertounknown anhydride of 11- carboxybenzanthrone has been prepared. The latter has also been formed by the action
of mercuric cyanide on the acid chloride. The structure
has been confirmed by chemical methods and a tentative
explanation of its formation in the above reactions given.
The new ethyl benzanthrone-11-carboxylate has been synthesised in the course of this work.
The possibility of the utilisation of the Ullmann
reaction in the synthesis of 1:11-disubstituted benzanthrones has been explored. It is concluded that 1:2-disubstituted naphthalene compounds such as methyl 1-bromo-2-naphthoate and 1-iodo-2-methylnaphthalene are
of little practical use in the formation of phenylnaphthyl derivatives of the required type while 1:8-disubstituted naphthalene compounds can, in a number of cases,
be utilised very successfully in the Ullmann reaction.
Employing methyl 8-bromo-7-rnethoxy-1-naphthoate as one
of the components in the Ullmann reaction, two new
phenylnaphthyl derivatives, methyl 7-methoxy-8-(o-nitro-phenyl)-l-naphthoate and methyl 7-methoxy-8-(o-nitro-pcarboethoxyphenyl)-l-naphthoate, have been synthesised
and, from these, two 1:11-disubstituted benzanthrones,
11-nitro-l-methoxybenzanthrone and 11- nitro-9-carboxy-lmethoxybenzanthrone, prepared. By using milder conditions
of cyclisation than needed to produce the latter benzanthrone, the corresponding ester, 11-nitro-9-carboethoxyl-methoxybenzanthrone, has been obtained. Several naphthalene derivatives not listed in the literature have
been synthesised in the course of the present work and
improved methods for the preparation of some halogenocompounds worked out.
It has been concluded that a primary condition determining the capacity of a halogeno- naphthalene derivative to interact with a halogeno-benzene derivative in
the Ullmann reaction to give compounds of the type under
consideration lies in the 1:8-substituted character of the
naphthalene molecule. It has also been shown that, in
all probability, this characteristic does not depend on the activation of the halogen by the peri-substituting
group alone. The empirical nature of work of this kind
has been emphasised.
An examination of the 1:11-disubstituted benzanthrones synthesised has proved that they exhibit abnormalities in their reactions due to the close spatial
proximity of the substituting groups. It has been demonstrated that the methoxyl group in 11-nitro-l-methoxybenzanthrone is hydrolysed under conditions which normally would leave such a grouping unaffected.
Confirmation has also been supplied to the hypothesis
of Rule and Smith (J., 1937, 1099) that, in the formation
of anthanthrone by a dinaphthyl dicarboxylic ester by use
of sulphuric acid, the red solution contains a benzobenaanthrone carboxylic eater and not, as Kalb stated, (Ber.,
1914, 47, 1724), a benz.obenzanthrone carboxylic acid.
The possibility of optical isomerism occurring in
1:11-disubstituted benzanthrones due to the disposition
of the closely adjacent substituting groups has been investigated, attempts having been made to resolve 10:11-benzobenzanthrone-l'-carboxylic acid, 11-carboxybenzanthrone-l-menthylamide and 11-nitro-9-carboxy-l-methoxybenzanthrone. No definite resolution of any of these
has been effected although, in the strychnine and cinchonine salts of the last- named, some slight evidence of
activity appears to have been detected. In the case of
the parent acid itself, however, it has been concluded
that optically active forms are incapable of existence.
A tentative explanation of this has been advanced but it
is pointed out that negative results in work of this
nature are essentially provisional and that further research upon this point is required.
It has been demonstrated that the utilisation of
chromatographic adsorption methods in the purification
and separation of benzanthrone derivatives and allied
compounds gives very satisfactory results. 11-Carbobenzanthrone-l-menthyrlamide has been purified readily
by this method where the normal methods. failed; ethyl
benzanthrone-11-carboxylate has been isolated from the
esterified mixture produced in the alkaline hydrolysis
of 1:11-ketobenzanthrone in quotable yield where fractional crystallisation of the mixture has previously
failed, and two new compounds of the dinaphthyl type
have been initially purified with greater facility than
would have been the case had the usual methods. been