Methods have been developed for the synthesis of 1,3,6,8-tetraazapyrene based on the reaction of 1,4,5,8-tetraaminonaphthalene with formic acid [1] and the synthesis of 2,7-dimethyl-1,3,6,8-tetraazapyrene based on the reaction of 6,7-diamino-2-methylperimidine with acetic anhydride [2]. These methods involve the use of not readily available starting reagents and are not general. In the present work, we propose a method for the synthesis of such compounds from available perimidine ketones 1a-c. Heating ketone 1a-c (1 mmol) and NaN 3 (0.26 g, 4 mmol) in PPA (2-3 g) at 70-80°C for 1 h and then at 100-110°C for 4 h with monitoring by thin-layer chromatography leads to 1,3,6,8-tetraazapyrenes 4a-c in 31-44% yield. The PPA sample containing 87% P 2 O 5 was prepared according to Uhlig [3].This reaction involves the intermediate formation of amides 2a-c, whose amination using sodium azide in PPA, as previously described for perimidines [4,5], leads to dihydro derivatives 3a-c, which are oxidized by atmospheric oxygen to give tetraazapyrenes 4a-c. 1-4 a R = R 1 = Me, b R = R 1 = Ph, c R = Ph, R 1 = Me

It is known that the halogenation of quinoline in strongly acidic medium occurs at position 5 and 8 forming a 1:1 ratio of isomers. It is thought that such an orientation is a consequence of the deactivation of the pyridine ring due to protonation [2,3].In the case of less strong acid the quinoline is initially substituted at position 3 and then at position 6 and 8 and this arises from its initial conversion to the quinolinium cation which reacts with a nucleophile at position 2 to form a 1,2-dihydroquinoline. Subsequent addition of the electrophile occurs at position 3 etc [2, 3].2,3'-Biquinoline was of interest as a model compound for the investigation of electrophilic substitution in quinolines because, as a result of its asymmetry, a monoprotonation principally at one of the nitrogen atoms might be expected. In this case the reaction of a first kind would occur on a nonprotonated quinoline fragment and permit an evaluation of the regioselectivity of the electrophilic substitution in the quinoline free base and in the second kind on the other ring.We have previously shown [4] that the 2,3'-biquinoline 1 is nitrated by potassium nitrate in sulphuric acid on the 2-quinoline fragment and this agrees with a direction of monoprotonation of 2,3'-biquinoline at the nitrogen atom in position 1'. With the above in mind the halogenation of 2,3'-biquinoline in the presence of acid would be expected to occur in the 2-quinoline fragment at positions 5 and 8. In fact, treatment of compound 1 with bromine or chlorine in sulphuric acid in the presence of Ag 2 SO 4 gives a mixture of the 8-halo-2,3'-biquinoline 2, the 5-halo-2,3'-biquinoline 3, and the 5,8-dihalo-2,3'-biquinoline 4 in the ratio 2:1:4 (from 1 H NMR spectroscopic data).

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Quinoline derivatives R 0410 Investigations on 2,3'-Biquinoline. Part 17. Regioselectivity of the Halogenation of 2,3'-Biquinoline Derivatives. -(DEMIDOVA, N. V.; KARAIVANOV, N. T.; GONCHAROV, V. I.; AKSENOV, A. V.; Chem. Heterocycl. Compd. (N. Y.) 41 (2005) 9, 1167-1172; Stavropol State Univ., Stavropol' 355009, Russia; Eng.) -C. Hettrich 28-135