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The preparation, chemical properties and synthetic utility of nitrogen heterocyclic diazo compounds are reviewed. IBTRODUCTIOB : Heterocyclic diazo compounds (1) and their diazonium salts (2) are versatile reagents and their chemistry ha8 received a considerable recent attention!" However, in spite of their interesting synthetic potentialities, the chemistry of this class of compounds has been ignored in available organic chemistry bocks. Moreover, with exception of Tedder's chapter in "Advances in Heterocyclic Chemistryn5which is now obsolete, no trials to review the chemistry of this class of compounds has been made. In the following we report the literature in this area which we hope will be of value for both researchers and imtmctors of organic chemistry. PREPATtATIOB : The common method for the synthesis of heterocyclic diazo compounds or diazonium salts is the diazctization of heteroaromatic primary amines in which the amino group is bonded directly to the ring (cf. Bq. 1). Entler4 has covered in details this m b -5 ject. Stadtler et a 1 reviewed the other methods for the synthesis of this class of compounds, but these methods are of minor importance. bese Y-Z .2 -1 HC1 --Eq. 1 CHEXICAL PROPERTIES: The diazo compounds can be converted into other derivatives. The reactivity and types of reactions undergone by these compounds are 8ummarisr.d in this review. 1. Intramolecular cyclization: Heterocyclic diazo compounds are considered as dipolar compounds. Thus, interaction between the positive and negative ends of the molenrle leads to the formation of fused Diazotization of 4-duo-3-phenyl-5-benzylpyrazole (2) has afforded the corresponding diazopyrasole derivative (4). Compound 4 when heated in 8 acetic acid has afforded the pyraeolo 3,4-c pyrasole derivative (5). Similarly, the pyrazolo 3,4-e -1,2.3,4-tetrazine (6) has been formed when a solution of diazotised 5-amino-4-phenylazopyrazole was left to stand at room temperature in protic media. One of the most efficient routes for the synthesis of aeopurinee is the self coupling of diazotized dnoimidazole.derivatives via amide or amidic nitrogen at 5-poaition.l0 Recently a survey of this synthetic route for obtaining derivatives of these ring systems has been reviewed!' 3-A1nino-4-methylquinoline (1) reacts vith two molecules of nitrous acid to form the quinolino-O-triazine derivative (g) aud 1 2 * 1 3 On the other hand, when the reaction 3-azidoquinolino-4-carboxaldehyde (2).was carried out in the presence of aulphuric acid, compound 10 was formed. 6-Rethyluracil (11) behaves similarly on diazotization13 (cf. Chart 1).

Several new visnaginone ethers were prepared and their thiosemicarbazone derivatives are synthesized. The behavior of the thiosemicarbazones in methanolic sodium methoxide and hydrochloric acid is discussed. Structures were established on the bases of elemental and spectral data studies. Some of the thiosemicarbazones were tested for their antimicrobial activity. The structures of the synthesized derivatives (5a-g,6a-g) were confirmed by means of IR, 1H NMR, MS and elemental analyses. The synthesized derivatives (5a-g,6a-g) wear subjected to the Microbiology Division, Microanalytical Center, Cairo University, (5a-g,6a-g) showed a variable degree of antimicrobial activity.

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