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Several tetrazole derivatives have been prepared from 7‐amino‐2‐hydroxy‐3‐phenyl‐1,8‐naphthyridine (Id). Evidence is presented to demonstrate that the tetrazole ring structure is the dominant species in the solid state and in alkaline solution while the open‐chain azido form dominates in acidic solution. In addition it has been shown that the presence of a phenyl group in a position adjacent to the tetrazole nucleus apparently stabilizes the tetrazole ring.

Die Nitrierung der Naphthyridine (I) in Schwefelsäure ergibt je nach verwendetem HNO3‐Überschuß die Mononitroderivate (II) und (III) (Naphthyridin: HNO3 = 1: 1,1) oder die Trinitroderivate (IV) und (V) (1:6).

Nitration of anthyridine-2,6-dione (I) gave 7-nitroanthyridine-2,6-dione (11). Treatment of this compound with phosphorus pentasulfide afforded 7-aminoanthyridine-2,6-dithione (111).Desulfurization of the thioderivative 111 with Raney Nickel and subsequent aromatization of 3-amino-5,lO-dihydroanthyridine (VI) in boiling nitrobenzene, gave 3-aminoanthyridine (VII) in satisfactory yield. The structure of 3-aminoanthyridine was demonstrated and its physicochemical features are not in agreement with that previously reported in literature. The preparation of 3-aminoanthyridine-5-one (XII) is also described.Previously T. Takahashi and coworkers (1) described the isolation of 3aminoanthryridine (VII) by treatment of S-amin0-2,2'-dipyridilamine hydrochloride with oxalic acid and glycerol at 130". 3-Aminoanthyridine is reported to be a colourless solid melting at 125-128". No other physicochemical data were reported by Takahashi and no structural proof was given. We recently reported the syntheses of several anthyridine derivatives (2a,b,c,d,e) and also the preparation of the parent nucleus (3) (m.p. 295.297"). The structures of these compounds were unequivocally assigned based upon chemical and physical evidence. In general, these substances are very highmelting crystalline solids, slightly soluble in the usual organic solvents. The relatively low melting point of the product isolated by Takahashi led us to repeat the reaction. However, various attempts to prepare the substance melting at 125-128" failed giving almost quantitative recovery of starting material.

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