Idarac,Diamant,France,1976
Step A: Ortho-Trifluoromethylanilinomethylene Ethyl Malonate - A mixture of
54.8 grams of ortho-trifluoromethylaniline and 73.5 grams of
ethoxymethylene ethyl malonate was heated to 120°C under an inert
atmosphere and maintained for 1 hour at this temperature while distilling off
the ethanol formed. The mixture was cooled and the elimination of ethanol
was completed by distillation under reduced pressure. The mixture was cooled
to obtain 115 grams of ortho-trifluoromethylanilinomethylene ethyl malonate
which was used as is for the following stage. A sample of the product was
crystallized from petroleum ether (BP = 65° to 75°C) to obtain a melting point
of 94°C.
Step B: 3-Carbethoxy-4-Hydroxy-8-Trifluoromethylquinoline - A mixture of 113
grams of crude ortho-trifluoromethylanilinomethylene ethyl malonate from
Step A, and 115 cc of phenyl oxide was heated rapidly under an inert
atmosphere. At about 195°C, the ethanol formed began to distill off. At the
end of about 30 minutes, the interior temperature reached 250°C and the
reaction mixture was heated to reflux. Reflux was maintained for 1 hour and
the mixture was then cooled, 25 cc of acetone were added and the mixture
was allowed to crystallize. The mixture was filtered and the crystals thus
formed were washed and dried to obtain 71.5 grams of 3-carbethoxy-4-
hydroxy-8-trifluoromethylquinoline with a melting point of 210° to 214°C,
which was used as is for the following stage. A sample of this product was
crystallized from ethanol to show a melting point of 216°C.
Step C: 3-Carboxy-4-Hydroxy-8-Trifluoromethylquinoline - 70 grams of crude
3-carbethoxy-4-hydroxy-8-trifluoromethylquinoline, obtained in Step B, were
introduced under an inert atmosphere into a mixture of 300 cc of water and
100 cc of aqueous 10 N solution of sodium hydroxide. The reaction mixture
was heated to reflux and maintained there for 2 hours and forty-five minutes.
The solution obtained was poured over a mixture of water, ice and 100 cc of
aqueous 11.8 N solution of hydrochloric acid. The precipitate thus formed was
isolated by filtration, washed with water and introduced into a solution of 20
grams of sodium bicarbonate in 2 liters of water.
The mixture was heated to 90°C and filtered to remove slight persisting
insolubles. The filtrate was acidified with acetic acid to bring the pH to about
5.5 and the precipitate formed was isolated by filtration, washed and dried to
obtain 58 grams of 3-carboxy-4-hydroxy-8-trifluoromethylquinoline having amelting point of 290° to 292°C, which was used as is for the following stage.
A sample of the product was crystallized from hot and cold acetone, treated
with charcoal to obtain pure 3-carboxy-4-hydroxy-8-trifluoromethylquinoline
having a melting point of 292°C.
Step D: 4-Hydroxy-8-Trifluoromethylquinoline - Under an inert atmosphere,
56.5 grams of crude 3-carboxy-4-hydroxy-8-trifluoromethylquinoline, obtained
in Step C were introduced into 110 cc of phenyl oxide. The reaction mixture
was rapidly heated to reflux and maintained at reflux for an hour and fifteen
minutes. The reaction mixture was cooled to about 50°C and 20 cc of
isopropyl ether were added thereto. The mixture was cooled to 20°C and
allowed to crystallize. The precipitate formed was isolated by filtration,
washed and dried to obtain 45.8 grams of 4-hydroxy-8-
trifluoromethylquinoline having a melting point of 180°C. A sample of this
product was crystallized from acetone, treated with charcoal to obtain pure 4-
hydroxy-8-trifluoromethylquinoline having a melting point of 180°C.
Step E: 4-Chloro-8-Trifluoromethylquinoline - 44.3 grams of crude 4-hydroxy-
8-trifluoromethylquinoline obtained in Step D were introduced in small
amounts into 130 cc of phosphorus oxychloride and then the reaction mixture
was held for 15 minutes at ambient temperature and heated to reflux and
maintained at reflux for 1hour. The mixture was cooled and excess
phosphorus oxychloride was removed by distillation under reduced pressure.
Water, ice, and then 80 cc of aqueous solution of ammonia at 22°Be were
added to the residue and the mixture was stirred and the aqueous phase was
extracted with ether. The ethereal extracts were washed with a dilute aqueous
solution of ammonia, then with water, dried, treated with charcoal and
concentrated to dryness to obtain 45.4 grams of 4-chloro-8-
trifluoromethylquinoline having a melting point of 78°C, which was used as is
for the preparation of 4-(ortho-methoxycarbonylphenylamino)-8-
trifluoromethylquinoline. A sample of crude 4-chloro-8-trifluoromethylquinoline
was crystallized from petroleum ether (BP = 65° to 75°C) to get a product
with a melting point of 78°C.
