1.2.4- Triazines versatile method

The most versatile method, for the preparation of this ring system is the condensation of an a-halocarbonyl compound with a 3-amino-l,2,4-triazine. For example, treatment of 3-amino-5,6-dimethyI-l,2,4-triazine (565) with phenacyl bromide (512) produced only (566) (65JHC287). In addition to a-hdoketones, a-haloaldehydes (72JHC1157, 55MI41000), a-haloacetals (80MI41000) and a-haloesters (79CHE1255) have been used. The direction of condensation is always as shown for the preparation of (566). 

There are many methods known for the synthesis of fully conjugated (aromatic) and nonaromatic 1,2,4-triazines. Most methods used for the preparation of 1,2,4-triazines utilize the formation of two C —N bonds in the ring-closure step, usually employing 4- and 2-atom fragments. The most often used route in the 1,2,4-triazine series is the combination of the N1-N2-C3-N4 fragment with the C5-C6 fragment, but the combination of N1-N2 with C3 — N4-C5 — C6 also is a versatile route. In addition to these routes the combinations C3 plus N4-C5-C6-N1-N2 and N4 plus C5-C6-N1 -N2-C3 are also used for the preparation of 1,2,4-triazines. 

Reduction of 1,2,4-triazine 4-oxides by trivalent phosphorus compounds or by sodium hydrogen sulfite is a versatile method for the preparation of 5-unsubstituted 1,2,4-triazines.126 241 The synthesis of 1,2,4-triazine 4-oxides is discussed in Section 2.2.1.1.4. 

This paper deseribes a rapid and versatile on-line-SPE LC-MS/MS method developed for the determination of various pestieides and tlieir metabolites in water. 28 pestieides, ineluding various triazines, phenylureas, organophosphorous eompounds and other speeies, were seleeted for systematie investigations. 

The 1,2,4-substituted triazine core is a versatile scaffold to access a wide range of condensed heterocyclic ring systems via intramolecular Diels-Alder reactions with a vast array of dienophiles. The triazine ring system is also a key component of commercial dyes, herbicides, insecticides and also recently appeared in medicinal chemistry. One way to synthesise triazines is to use a three-component reaction that has been described in the literature several times, both under traditional thermal heating and under solvent-free microwave-assisted conditions42. However, the previously described methods focussed only on simple aliphatic phenyl and ester substituents. 

One extraction phase developed for triazines is graphitized carbon black, which has been shown to be versatile for a wide range of pesticides (Di Corcia et al, 1987 Di Corcia and Marchetti, 1992 Di Corcia et al., 1993 Bucheli et al, 1997 Crescenzi et al, 1997). It has also been shown to be very effective for retaining the more polar metabolites (e.g., deisopropylatrazine (DIA), deethylatrazine (DEA), and hydroxyatrazine (ATOH) see Table 20.1, also Appendix, Table A3) (Berg et al, 1995 Di Corcia et al, 1997 Pichon et al, 1995 Schulein et al., 1995). The methods published require considerably more column preparation and elution steps than traditional Cl8 methods. Pichon et al. (1995) also included the polar triazine metabolites ammeline, ammelide, and cyanuric acid, with good recoveries using a graphitic carbon sorbent. 

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