Organic Syntheses, Coll. Vol. 5, p.493 (1973); Vol. 41, p.46 (1961).
B. Diphenaldehydic acid
. A mixture of 10 g. (0.0368 mole) of 3,8-dimethoxy-4,5,6,7-dibenzo-1,2-dioxacycloöctane
, 50 ml. of 10% sodium hydroxide
solution, and 200 ml. of 95% ethyl alcohol
is heated under reflux for 15 minutes, during which time the solid dissolves (Note 3)
. The solution is cooled, acidified with concentrated hydrochloric acid
, and diluted to the cloud point with water. Crystallization is induced by rubbing the side of the vessel with a stirring rod (Note 4)
. More water is then added slowly until crystallization is complete. Filtration yields 6.7–7.3 g.
) of colorless to yellowish crystals melting at 130–132°
. Recrystallization from 100 ml. of 1:1 methanol-water gives an 80–95%
recovery of diphenaldehydic acid
melting at 134–135° (Note 5)
, (Note 6)
, and (Note 7)
The trituration is carried out at room temperature, but the mixture is cooled before filtering. The product can be recrystallized from methyl ethyl ketone
, but this requires large volumes of the solvent and is unnecessary.
After solution has occurred, 1 ml. of the solution is acidified and tested with sodium or potassium iodide
. If no iodine
is released, the reaction is complete.
If the solution resists crystallization, it can be evaporated one-half or tow-thirds of its volume and cooled further. The checkers found that, if product was allowed to oil out and solidify, the subsequent purification was rendered more difficult.
Often recrystallization is unnecessary since the first crystalline product melts at 134–135°
. The yields then are 81–84%
If sodium hydroxide
is omitted in this preparation and the reaction mixture is refluxed until it no longer gives a positive peroxide test with iodide ion (Note 3)
(about 2 hours), the product is the methyl ester of diphenaldehydic acid
yield (m.p. 50–51°
If, in the reaction mixture described, twice the volume of 10% sodium hydroxide
solution and 25 ml. of 30% hydrogen peroxide
are employed and the reaction mixture is refluxed until it no longer gives a positive peroxide test with iodide ion (about 30 minutes to 1 hour), the product is diphenic acid
) in 73–85%
The method here described is based on the reported ozonolysis of phenanthrene
, followed by conversion of the initial ozonolysis product to diphenaldehyde
), diphenaldehydic acid
, methyl diphenaldehydate (Note 6)
, and diphenic acid (Note 7)
.2 Diphenaldehydic acid
has previously been made in low yields by oxidative decomposition of the monohydrazide of diphenic acid
The presently described method is far superior, not only in yield, but also in simplicity.
has been prepared by the reduction of diazotized anthranilic acid
with cuprous ion,5
Ullman coupling of potassium o-bromobenzoate
and oxidation of phenanthrene
with various oxidizing agents.7
The latter methods have been reviewed recently.7
The ozonolysis method has also been carried out in solvents8
that do not react with the zwitterion intermediate.9
Of the various routes to diphenic acid
, the present method and the peracetic acid
oxidation of phenanthrene7
seem to be the simplest. The yields are equally good.
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