82 (1963) RECUEIL 1047

547.678.3:615 9-PYRIDYLIDENEFLUORENES,

A NEW CLASS OF ANTI-INFLAMMATORY SUBSTANCES

BY

N. 1’. BUU-HO.f, F. DELBARRE, P. JACQUIGNON, H. BROUILHET, A. ROSE, J. F. SABATHIER, AND M. P. SINH

Centre de Recherches sur les Maladies osteoarticulaires (I.N.H.), Hbpital Cochin, Paris, and Institut de Chimie des Substances Naturelles du C.N.R.S., Gif-sur-Yvette (S.-el-O.), France.

The condensation of fluorene with the three formylpyridines and 2-formyl- 6-methylpyridine has been investigated, and the 9-pyridylidenefluorenes obtained have been tested in rats for anti-inflammatory activity. 9-(3-Pyridylidene)fluo- rene proved the most potent compound, with an activity half of that of subcuta- neously injected prednisone, in an oral dose ten times greater.

Most known anti-inflammatory agents are either molecules of the steroid type (e.g. cortisone and derivatives) or belong to the pyrazolone and di- oxopyrazolidine series (e.g. phenylbutazone) However, within the last few years, compounds endowed with significant anti-inflammatory activity have been found in chemical families completely unrelated to these two main groups. Thus, in the group of anthranilic acids, N-(2,3-xylyl)- and N- (3-trifluoromethylphenyl)-anthranilic acid have both proved of interest in this respect 2 , and, more recently, Sarett and his coworkers reported that l-(p-chloroben~~oyl)-5-methoxy-2-methylindole-3-acetic acid (indomethacin) showed in animal tests an anti-inflammatory activity ranging from 10 to 85 times that of phenylbutazone 3 .

In the framework of a general investigation on anti-inflammatory and analgesic properties of triarylethylenes and analogues, we have synthesised and investigated several condensation-products of fluorene with aldehydes of the pyridine group. Condensation proceeded smoothly in the presence of alkaline catalysts (potassium hydroxide and piperidine), using an azeo-

S e e : Walter Krohs and Ofto Hensel “Pyrazolone und Dioxopyrazolidine”, Editio Cantor, Aulenclorf i Wurtt., 1961. C. V. Winder, J . Wax, L. Scofti, R. A . Scherrer, E. M. Jones, and F. W. Shorf, J. Pharm. Exper. Therapeutics 138, 405 (1962); French Drug Patent No. 1341 M (11.8.1961) to I’arke, Davis & Co. T. 1’. Shen, T. B. Windholz, A . Rosegay, B. E. Witzel, A . N . Wilson, J. D. Willetf, W. J . Holtz, R. L. Ellis, A . R. Mafzuk, S. Lucas, C. H. Stammer, F. W. Holly, L. H. Sarcw, E. A . Risley, G. W. Nuss, and C. A. Winfer, J. Am. Chem. SOC. 85,488 (1963).

-~

1048 N. P. Buu-Hoi, F. Delbarre, P. Jacquignon, H . Brouilliet, A. Rose, etc.

tropic method for removal of the water formed in the course of the reaction. The aldehydes used were 2-, 3-, and 4-formylpyridine, and 2-formyl-6- methylpyridine. The compounds obtained were pale yellow, weak bases, which yielded readily hydrolysable hydrochlorides. The structure of these products can probably be represented by formulae I-V; the elementary analyses are in accordance with this view. This type of condensation could also be effected with 2-nitrofluorene;

0; CH

I CH CH

I; R = R ’ = H 11; R = H, R = CHI

111; R = NOz, R‘ = H

thus, with 2-formylpyridine, compound (111) was readily obtained. The anti-inflammatory activity of the three isomeric compounds (I),

(IV) and (V) was determined by the Hillebrecht method 4 , which consists of measuring the effect of the compounds tested on the acute rat-paw oedema induced by injection of suspensions of kaolin. The compounds tested, in the form of their hydrochlorides, were given orally in a dosage of 300 mg/kg. The evolution of the oedema was followed during its ascending phase, i.e. during the four hours immediately following injection of kaolin, by determining the increase in volume of the paw. Results showed 9-(3- pyridy1idene)fluorene (IV) to be the most active, followed by 9-(4-pyriclyl- idene)fluorene (V), with compound (1) being the least active. Comparison with prednisone (administered subcutaneously in a dose of 25 mg/kg) showed that the hydrochloride of (IV) (in an oral dosage ten times greater) was half as active. In acute toxicity determinations, the hydrochloride of compound (IV) showed an oral ~ ~ 5 0 of 2.6g/kg in mice.

Experimental (M.p.s uncorrected and taken on Maquenne block)

9-(2-Pyridylidene)Ruorene (I) A solution of 2-formylpyridine (12.8 g), fluorene (16.6 g), and a few drops of piperidine

in xylene (50 ml) was slowly refluxed, with removal of the water-xylene azeotropic mix- ture. After cooling, water was added, the reaction-product taken up in chloroform, the

J. Hitlebrechf, Arzneimittel-Forsch. 4, 607 (1954).

9-P.yridylidenefluorenes, A New Class, etc. 82 (1963) RECUEIL 1049

chloroform solution dried over calcium chloride, the solvent distilled, and the residue fractionated in vacuo. The portion b.p. 250-260'115 - 16 mm was recrystallised from cyclohexane to give yellowish piisms, m.p. 98". Yield: 40%.

Found : C 89.4 ; H 5.1 ; N 5.3 Calc. for CipH13N (255.30): ,, 89.38; ,, 5.13; ,, 5.49.

The hydrochloride was prepared by treating a hot solution of the base in ether with a saturated e t h e r d solution of hydrogen chloride. The precipitate formed was collected and washed several times with ether. It was a yellow microcrystalline powder, m.p. 163-164" (decomposition > 120").

Found : C1 12.3 ; N 4.9 Calc. for CipHlsClN (291.77): ,, 12.17; ,, 4.80.

9-(3-Pyridylidene)fluorene (IV)

cyclohexane as pale yellow needles, m.p. 96", b.p. 260-265"/15 mm. Found : C 89.1 ; H 5.4 ; N 5.5 Calc. for CipHiaN (255.30): ,, 89.38; ,, 5.13; ,, 5.49.

Prepared in 50-60 % yield from 3-formylpyridine, as for the 2-isomer; crystallised from

Hydrochloride: yellow microcrystalline powder, m.p. 161". This salt underwent con- siderable hydrolysis in protic solvents.

Found Calc. for CIOHLICIN (291.77): ,, 12.17; ,, 4.80.

: CI 12.2 ; N 4.6

9-(4-Pyridylidene)fluorene (V)

cyclohexane and benzene as pale yellow prisms, m.p. 135-136", b.p. 270-275"/14 mm. Prepared in 45 % yield from 4-formylpyridine, this base crystallised from a mixture of

Found : C 89.5 ; H 5.3 ; N 5.5 Calc. for C ~ ~ H I B N (255.30): ,, 89.38; ,, 5.13; ,, 5.49.

Hydrochloride: yellow microcrystalline powder, m.p. 202" (decomp. > 130-135'). Found Calc. for C I O H ~ ~ C I N (291.77): ,, 12.17; ,, 4.80.

: CI 12.4 ; N 4.7

9-(6-Methyl-2-pyridylidene)fluorene (11)

from ether as fine yellow needles, m.p. 88". Found : N 5.0 Calc. for C Z O H ~ ~ N (269.33): ,, 5.20.

Prepared in pcior yields (30 %) from 6-methyl-2-formylpyridine, this base crystallised

Hydrochloride: very unstable yellow microcrystals, m.p. 117" (decomp. > 90'). Found Cak. for ( ~ Z O H I & ~ N (305.79): ,, 11.26; ,, 4.58.

: C1 10.8 ; N 4.9

2-Nitro-9-(2-pyridylidene)fluorene (111)

Condensation of 2-nitrofluorene (21.1 g) and 2-formylpyridine (12.8 g) was effected as for compound (I). After the reaction, water was added, the xylene steam-distilled, and

1050 N . P. Buu-Hoi and co's, 9-Pyridylidenefluorenes, A New Class, etc.

the red resin which remained was taken up in methanol and the methanol solution boiled with charcoal. Concentration of the solution gave a precipitate (30% yield), which re- crystallised from cyclohexane as yellow ,needles, m.p. 136".

Found : C 75.9 ; H 4.3 ; N 9.2 Calc. for ClgHlzNzOz (300.30): ,, 75.99; ,, 4.03; ,, 9.33.

(Received June 25th. 1963).