Hofmann and Behrmann have already shown (Ber., 1884 17, 2696) that dichloroisonicotinic acid is reduced by hydriodic acid in sealed tubes to isonicotinic acid. In repeating this experiment, it was found that when dichloroisonicotinic acid was boiled with strong hydriodic acid in open vessels, a substitution, and not a reduction, takes place, the product being 2: 6-diiodoisonicotinic acid.

The silver salt of dichloroisonicotinic acid, on being gently heated in a current of carbon dioxide in the manner described by Königs and Körner (Ber., 1883, 16, 2153), yields a dichloropyridine, which sublimes in colourless, feathery scales, and after crystallisation from dilute alcohol melts at 87-88° (uncorr.). This compound is identical with the dichloropyridine obtained by the action of phosphorus pentachloride on dry pyridine (Trans., 1898, 73, 433). Its non-basic character is in marked contrast to the basic properties of the only isomeride so far described, and of certain of the more highly chlorinated derivatives of pyridine-a fact which supports the view held as to its constitution (compare this vol., 1.)

EXPERIMENTAL.

Tetrachloro-2-aminopyridine from B-Hydroxyglutaramide.

On the authority of Anschütz (Richter's Organische Chemie., Ed. 1898, ii, 573), it is stated that ẞ-hydroxyglutaramide, on treatment with phosphorus pentachloride, yields trichloro-2-aminopyridine melting at 144-145°. In view of the general behaviour of this class of compounds, it seemed probable that the remaining hydrogen atom of the nucleus might be replaced by chlorine without difficulty by means of phosphorus pentachloride at a higher temperature. As no record could be found of the experiments on which the statement of Anschütz is based, the operation was carried out as follows.

Diethyl ẞ-hydroxyglutarate was poured into a large excess of strong aqueous ammonia, in which it gradually but completely dissolved in the cold. After standing for two days, the water and excess of ammonia were removed in a vacuum over sulphuric acid, the semisolid mass drained by the aid of the filter pump, and washed with small quantities of spirit, in which the diamide is only sparingly soluble. The nearly colourless product was heated with excess of phosphorus pentachloride in a reflux apparatus for 3-4 hours, then poured into water, and finally distilled with steam. The colourless crystals filtered off from the distillate were frequently crystallised from dilute alcohol, and consisted chiefly of a compound melting at 143-144° (uncorr.), a small quantity only of pentachloropyridine being obtained. The substance melting at 143-144°, on further treatment with excess of phosphorus pentachloride (2 mols.) in sealed

tubes at 220-230° and subsequent distillation with steam, yielded tetrachloroaminopyridine, which, after purification from alcohol, melted at 174-175° (uncorr.). On analysis:

0.1067 gave 0.2660 AgCl. Cl=61.34.

0.1012

10.16 c.c. nitrogen at 15° and 770 mm. N=11.91. CH2NCI requires Cl=61.14. N=12.06 per cent.

2

This compound crystallises from alcohol in long needles and is soluble in the usual organic solvents. Water and dilute mineral acids dissolve it slightly on boiling. It is easily soluble in cold strong sulphuric acid, and is reprecipitated on diluting. Strong nitric acid decomposes it at the ordinary temperature. It is not acted on by cold alkalis, and volatilises only slowly in steam.

Tetrachloro-2-aminopyridine from Citrazinic Acid.

Chloroaminoisonicotinic acid, prepared from citrazinic acid (Ber., 1884, 17, 2694; Trans., 1897, 71, 1075), was heated in sealed tubes at 210-220° for 4 hours with excess of phosphorus pentachloride. The product was poured into water and distilled with steam. The light, feathery crystals from the distillate, on purification from spirit, melted at 174-175° (uncorr.). On analysis:

0.1992 gave 12.5 c.c. nitrogen at 17° and 750 mm. N = 12.01. 0.0761 0.1877 AgCl. Cl=60·99.

CH2NCI requires Cl = 61.14. N=12.06 per cent.

2

The properties of the compound thus prepared agree in every way with those of tetrachloro-2-aminopyridine described above.

6-Chloro-2-hydroxyisonicotinic Acid from 6-Chloro-2-aminoisonicotinic Acid.

Chloroaminoisonicotinic acid, dissolved in strong sulphuric acid, was mixed with a slight excess of sulphuric acid previously saturated with nitrous fumes. After heating for several minutes on the waterbath, the solution was slowly diluted, again heated on the water-bath, and finally poured into water. The precipitate, after purification by crystallisation from alcohol, was converted into the methyl ester, which, when recrystallised from spirit, melted at 189–190° (uncorr.). On analysis:

0.0733 gave 0.1202 CO, and 0.021 H2O. C-44-72; H=3.19. 0.1622 10-3 c.c. nitrogen at 16:4° and 771.6 mm.

0.0965

N=7.63.

CH2ONCI requires C = 44.80; H=3.20; Cl = 18.80; N = 7.46 per cent.

The acid is easily soluble in hot alcohol and in alkalis, sparingly so n boiling water and in ether, and insoluble in cold water and in dilute mineral acids. The compound prepared in this way is identical with the product of the action of caustic soda or potash on dichloroisonicotinic acid (loc. cit.), as is shown by the fusing point of the methyl ester.

6-Amino-2-hydroxyisonicotinic Acid from 6-Chloro-2-hydroxyisonicotinic Acid.

Chlorohydroxyisonicotinic acid, prepared as described above, was heated in sealed tubes for 4 hours at 170-180° with a large excess of strong aqueous ammonia. When cool, the contents of the tubes were diluted, acidified with hydrochloric or sulphuric acid, and any unchanged chlorohydroxyisonicotinic acid filtered off. The latter may also be easily removed by boiling with alcohol, in which it dissolves freely, whilst the solubility of aminohydroxyisonicotinic acid in alcohol is very small. After dissolving in alkali and reprecipitating by neutralisation with hydrochloric acid, a compound free from chlorine was obtained. On analysis:

0.1560 gave 23.9 c.c. nitrogen at 15° and 740 mm. CHON2 requires N = 18.18 per cent.

N=17.77.

This compound chars without fusing. It is very sparingly soluble in the usual organic solvents and in boiling water. Alkalis and dilute mineral acids dissolve it easily, and from these it is repre cipitated on neutralisation. The ammonium salt is dissociated when its solution is evaporated to dryness. The silver salt, obtained by the addition of silver nitrate to the ammonium salt in solution, crystallises in yellowish needles which blacken on warming. The lead salt is an insoluble colloid; the calcium and barium salts are soluble.

Tetrachloro-6-aminopyridine from 6-Amino-2-hydroxyisonicotinic Acid. Aminohydroxyisonicotinic acid was heated in sealed tubes at 230-240° for several hours with excess of phosphorus pentachloride. On cooling, the product was poured into water, distilled with steam, and purified in the manner already described. The recrystallised substance melted at 174-175° (uncorr.). On analysis:

0-0602 gave 0.1495 AgCl. Cl-61.40.

CH,N,Cl, requires Cl=61.14 per cent.

The product obtained thus coincides in every way with 2-aminotetrachloropyridine prepared by any of the methods already described.

2: 6-Diiodoisonicotinic Acid from 2: 6-Dichloroisonicotinic Acid,

Dichloroisonicotinic acid was covered with sufficient fuming hydriodic acid to dissolve it completely on warming, and boiled in a reflux apparatus for half an hour. At the end of that time a copious, heavy, sand-like precipitate separated out, and was removed by filtration through a platinum cone, whilst a further quantity was obtained on largely diluting the filtrate. After recrystallising a few times from dilute alcohol, the acid melted at 195-196° (uncorr.). On analysis :

0.1393 gave 0-1005 CO, and 0.0105 H2O. 0.1485 0.1075 CO2 0.0115 H2O.

C=1967; H=0·85.
C=19.70; H=0·86.

CH2ONI, requires C=19.23; H=0·80; I=67.11 per cent,

This substance is more easily dissolved by alcohol than the corresponding chloro-derivative. Alkalis dissolve it freely, and from the solution it is reprecipitated by dilute acids, in which it is practically insoluble. Strong sulphuric or nitric acid dissolves it in the cold, and, as was shown by an iodine determination, it may be boiled with strong nitric acid without change. The ammonium salt crystallises in long needles, and is only sparingly soluble in cold water; the sodium and potassium salts are also sparingly soluble, and crystallise in slender, colourless needles. The calcium salt is moderately soluble in boiling water. The barium and lead salts are colloidal substances, which could not be obtained crystalline, although easily soluble in boiling water, and only sparingly so in cold. The ferric salt is an insoluble, yellow powder. The copper salt crystallises from water in beautiful, blue needles. The cadmium and gold salts are readily soluble in boiling, but insoluble or nearly so in cold water.

2: 6-Dichloropyridine from Dichloroisonicotinic Acid.

The addition of silver nitrate solution to a solution of ammonium dichloroisonicotinate yields a well-defined, crystalline silver salt, which may be crystallised unchanged from boiling water, a fact which has been made use of in the separation of dichloroisonicotinic acid from tetrachloroisonicotinic acid, the latter being invariably present in preparations of dichloroisonicotinic acid by any of the methods hitherto described.

The silver salt, purified and dried at 100°, was gently heated in a current of carbon dioxide. The light, feathery sublimate was collected and recrystallised several times from dilute alcohol, when it was obtained in colourless, pearly scales melting at 87-88° (uncorr.). On analysis:

0.1240 gave 10.3 c.c. nitrogen at 17° and 770 mm. N = 9.61, 0.1260 0.2436 AgCl. CI=47.93.

CH,NCI, requires N = 9.46; Cl=47.97 per cent.

This compound has already been isolated from the product of the interaction of phosphorus pentachloride on pyridine (Trans., 1898, 73, 437). The properties of the substance obtained in the manner shown above agree entirely with those already described.

UNIVERSITY CHEMICAL LABORATORY,

CAMBRIDGE.

XXIV. The Formation of Heterocyclic Compounds. By SIEGFRIED RUHEMANN and H. E. STAPLETON, Scholar of St. John's College, Oxford.

THE research on the formation of a-pyrone compounds (Ruhemann, Trans., 1899, 75, 245, and 411), by the action of ethyl phenylpropiolate on the sodium derivatives of ẞ-diketones and the ethyl esters of B-ketonic acids, induced one of us and A. V. Cunnington to examine the behaviour of organic bases towards the ethyl esters of the acids of the acetylene series, with the view of ascertaining whether in those cases also additive substances were formed which subsequently lost alcohol, and condensed to heterocyclic compounds. A few months ago (Trans., 1899, 75, 954) we published the first part of our investigations in this direction, and were able to show that by the interaction of benzamidine and ethyl phenylpropiolate a cyclic compound was produced. The constitution of this substance we represented by the symbol,

A closer examination of the reaction has led the authors of the present paper to the discovery of the following interesting fact. At the ordinary temperature, benzalphenylglyoxalidone is formed almost exclusively, but on digesting the mixture of the ethyl ester and the amidine on the water-bath, besides this substance another is produced which has been identified as diphenylpyrimidone,