Organic Syntheses, CV 5, 493
DIPHENALDEHYDIC ACID
Submitted by Philip S. Bailey and Ronald E. Erickson
1.
Checked by Carole L. Olson and John D. Roberts.
1. Procedure
A.
3,8-Dimethoxy-4,5,6,7-dibenzo-1,2-dioxacyclooctane. The ozonolysis of
10 g. (0.0562 mole) of phenanthrene in dry
methanol is carried out as described in the
diphenaldehyde preparation (
p. 489). The reaction mixture is not reduced, however, but is acidified with
1–3 drops of concentrated hydrochloric acid (Note
1) and allowed to stand at room temperature for an hour and then in the
refrigerator for several hours or overnight. Suction filtration yields
11.5–12.5 g. (
75–82%) of crystals melting at
178–181°. Trituration with
methyl ethyl ketone gives a
90–95% recovery of colorless crystals melting at
180–181° (Note
2).
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. (
81–88%) 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).
2. Notes
2. 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.
3. 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.
4. 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.
5. Often recrystallization is unnecessary since the first crystalline product melts at
134–135°. The yields then are
81–84%.
6. 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 in
91–98% yield (m.p.
50–51°).
2
7. 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 (m.p.
220–223°) in
73–85% yield.
3. Discussion
The method here described is based on the reported ozonolysis of
phenanthrene in
methanol, followed by conversion of the initial ozonolysis product to
diphenaldehyde (
p. 489),
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.
3,4 The presently described method is far superior, not only in yield, but also in simplicity.
Diphenic acid has been prepared by the reduction of diazotized
anthranilic acid with cuprous ion,
5 Ullman coupling of
potassium o-bromobenzoate,
6 and oxidation of
phenanthrene or
phenanthrenequinone with various oxidizing agents.
7 The latter methods have been reviewed recently.
7 The ozonolysis method has also been carried out in solvents
8 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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