Two new methods have been evolved for the
preparation In improved yields of 9-fluorenyl-2-
proplonic acid, from which fluoranthene has been
synthesised, thus confirming the work of von Braun.
The first of these methods resulted from
investigations of the trimethylbenzylammonium hydroxide
catalysed condensation of acrylonitrile with 9-substitutad fluorenes, the initial condensation in the
preparation of the above acid being with 9-fluorenol.
Acrylonitrile was also condensed with 9-phenylfluorene,
and the product hydrolysed to an acid cycllsable to
a ketone, but acrylonitrile could not be condensed
with 9-chloro-, 9-ethyl, and 9-benzylfluorenes, nor
with 1-keto-l'(9'-fluorenyl) acetic acid.
The first step in the second method was an
alkoxide catalysed condensation of dlethylsuccinate
and 9-fluorenone (a Stobbe reaction). An intensive
study was made of this reaction, so that the structure
of Its various products could be firmly established.
These were found to be the mono-condensation products,
3:3'-diphenylene-2-carbethoxyvinylacetic acid and the
dibasic acid, 3:3'-diphenylene-2-carboxyvinylacetic
acid whose structures were established by esterification, hydrolysis, reduction and bromination
experiments, and the dicondensation product 1:4-
bisdiphenylene-2:3-decarboxybutadlene whose structure
was elucidated by decarboxylation to the known hydro-carbon. Reduction of the lactone produced by the
decarboxylation of the mono-condensation products
gave the 9-fluorenyl-2-propionic acid.
It was found that fluorene condensed with
molecular amounts of cinnamnitrile (phenylacrylonitrile) under the catalytic action of trimethylbenzylammonium hydroxide and the product hydrolysed
to an acid cyclisable to a ketone.
It was also found that the 9-fluorenyl-2-
propionic acid, and the substituted 9-fluorenyl-2-
propionic acids prepared, were very resistant to
cyclisation, the only method from which crystallisable products were obtained being acid chlorideFrledel-Crafts methods.