1.2.3- Triazines, fused

The second chapter is by E. S. H. E) Ashry, N. Rashed, M. Taha, and E. Ramadan of Alexandria, Egypt. They contribute the first of a two-part essay on fused 1,2,4-triazines. The present chapter deals with triazines fused to heterocycles with three-, four-, and five-membered rings. In a subsequent volume of the series we will cover triazines condensed with six-membered and larger rings. 

Formation of the outer six-membered ring. This is illustrated for 1,2,4-triazine-fused systems in Scheme 96... 

The final chapter is Part II of the survey of condensed 1,2,4-triazines and is authored by E. S. H. El Ashry, N. Rashed, A. Mousaad, and E. Ramadan of Alexandria University, Egypt. The same group wrote Part I in Volume 59, which covered 1,2,4-triazines fused to heterocycles with 3-, 4-, and 5-membered rings. Part II continues the survey to cover 1,2,4-triazines fused to 6- and 7-membered rings and also those fused to two heterocyclic rings. 

Triazines. Fused 1,2,4-triazines are formed regioselectively by cocyclization of adiponitrile and a nitrile catalyzed by FeifCO), (equation I). 

In addition to the above, a number of other heterocyclic compounds, for example, 2-aroylbenzofurans, 1,3-benzoxathioles, dihydropyrans, 1,4-benzoxazines, hydantoin derivatives, piperazine-2,5-diones, thioethenes, 1-arylbenzimidazoles, benzofuran-1-oxides, piperazinones, thiazoles, 5-thiacyclohexanecarboxaldehyde, pyrroles, triazines, fused napthoquinone derivatives and P-lactams have been synthesised using PTC technique." ... 

SPME has been utilized for deterrnination of pollutants in aqueous solution by the adsorption of analyte onto stationary-phase coated fused-siUca fibers, followed by thermal desorption in the injection system of a capillary gas chromatograph (34). EuU automation can be achieved using an autosampler. Eiber coated with 7- and 100-p.m film thickness and a nitrogen—phosphoms flame thermionic detector were used to evaluate the adsorption and desorption of four j -triazines. The gc peaks resulting from desorption of fibers were shown to be comparable to those obtained using manual injection. 

This reactivity of A-unsubstituted amino-pyrazoles and -indazoles which can be regarded as 1,3-diamino derivatives has been used to build a great variety of fused six-membered heterocycles such as the 1,2,4-triazine derivatives (540) and (541), the 1,3,5-triazine derivatives (542) and (543), and benzothiadiazines (544). 

Condensed 1,2,4-Triazines I. Fused to Heterocycles with Three-, Four-, and Five-Membered Rings... 

In addition to the synthesis of industrially important azo dyes using heteroaromatic diazo components, intramolecular azo coupling reactions of heterocyclic diazonium ions also have interesting synthetic uses, because they lead to new fused-ring heterocycles, as shown by the diazotization of 2-amino-3-arylbenzimidazoles (12.7) in which, without isolation of the diazonium ion, a 1,2,4-triazine ring is formed (Kolodyazhnaya et al., 1973). Further examples of intramolecular azo couplings were reviewed by Tisler and Stanovnik (1980), and very extensively (403 references ) by Kishimoto et al. (1990). 

Triazines, Tetrazines and Fused Ring Polyaza Systems... 

Early work relied on the use of packed columns, but all modern GC analyses are accomplished using capillary columns with their higher theoretical plate counts and resolution and improved sensitivity. Although a variety of analytical columns have been employed for the GC of triazine compounds, the columns most often used are fused-silica capillary columns coated with 5% phenyl-95% methylpolysiloxane. These nonpolar columns in conjunction with the appropriate temperature and pressure programming and pressure pulse spiking techniques provide excellent separation and sensitivity for the triazine compounds. Typically, columns of 30 m x 0.25-mm i.d. and 0.25-qm film thickness are used of which numerous versions are commercially available (e.g., DB-5, HP-5, SP-5, CP-Sil 8 CB, etc.). Of course, the column selected must be considered in conjunction with the overall design and goals of the particular study. 

Lipophilicity and specific hydrophobic surface area were determined by using reversed-phase thin-layer chromatography for fused heterocyclic ring systems including five pyrido[2,iy][l,2,4]triazine derivatives <1998MI64>. 

Triazinethiones have been used frequently for the syntheses of triazino-triazines in the literature. Reaction of 6-methyl-5-[substituted styryl]-2/7-[l,2,4]triazine-3-thiones 39 with thiourea or acetylthiourea in dimethylformamide (DMF) led to the formation of N,N -disubstituted thioureas 40. Heating the compound 40b with glacial acetic acid and fused sodium acetate under reflux led to the formation of the compounds 4,7-dimethyl-8-[2-ethenylfuran]-2-thioxo-l,3,5-triazino[5,6- ][l,2,4]triazine 22 (Scheme 6) <2003PS279>. 

Systems with a triazine as the central ring. Equations (75)—(77) <1999JHC857, 2003JRM1161, 2005EJC325> and Scheme 60 <1996T3037> illustrate the range of cyclization methods that lead to these fused triheterocyclic systems. 

Triazines, tetrazines and fused ring polyaza systems... 

There are 12 isomeric structures for this ring system, where the triazine ring is directly fused to the pyrimidine nucleus of the quinazoline ring one of the nitrogen atoms of the quinazoline ring is located at the bridgehead of the bicyclic ring. 

There are three types of triazines that are fused to [1,2,4]triazine parent rings. These are the 1,2,3-, 1,2,4-, and 1,3,5-triazines, and each one is subdivided according to the site of fusion to the parent as indicated by the letter z in the general formulas used below. 

Condensed 1,2,4-Triazines II. Fused to Heterocycles with Six- and Seven-Membered Rings and Fused to Two Heterocyclic Rings E. S. H. El Ashry, N. Rashed, A. Mousaad, and E. Ramadan... 

Triazoles fused with larger aromatic systems can be also obtained this way. Thus, in an example given in Equation (30), 2i/-phenanthro[9,10-r/l-l,2,3-triazole 1221 is obtained in 84% yield from a reaction of 3-hydroxyphe-nanthro-l,2,4-triazine 1220 with NCS <2000H(53)203>. 

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