Triazines chemistry

The reaction of 3-(methylthio)-5-i -l,2,4-triazine with potassium amide/liquid ammonia was the first example in 1,2,4-triazine chemistry where the replacement of the methylthio group by an amino group was found to occur with important participation of the Sn(ANRORC) mechanism (75RTC204). This was proved by the experiment that the 3-amino-... 

There have been many developments in the chemistry of the 1,3,5-triazines since the comprehensive reviews of Smolin and Rapoport (59HC(13)1) and Modest (B-61MI22000, p.627). It is impossible to include all the vast range of 1,3,5-triazines reported in the literature 138 pages of the Compound Index in the Ninth Collective Index of Chemical Abstracts are dedicated to this system. This review will concentrate on the more important recent developments of 1,3,5-triazine chemistry, and reference will be made to previous reviews, or typical papers, to illustrate the better-known aspects of the subject. 

Before embarking on a discussion of recent developments in 1,3,5-triazine chemistry, it is appropriate to look at the 1,3,5-triazines in their historical context. Thus, the original syntheses and characterization of four of the more important compounds, 1,3,5-triazine, cyanuric chloride, cyanuric acid and melamine, will be discussed briefly. 

Building on these early developments, research in triazine chemistry has continued to result in the discovery of new compounds, including asymmetrical triazine herbicides and other classes of chemistry containing the triazine ring structure that are important for weed control around the world. 

Regulatory reviews and reregistrations involving herbicides in each of the classes of triazine chemistry are ongoing in individual countries around the world. This section will focus on the chlorotriazines since they have recently received the most comprehensive review. 

It has been only a half-century since better weed-control technology allowed most of us to escape from the drudgery of stoop labor. Without the triazine chemistry, there is little question that millions of us would have to go back into the fields with short-handled hoes. Our society would today be substantially less sustainable and our wildlands and wild species would face far greater pressures from the plows of low-yield farmers. 

In triazine chemistry, sulfone is a better leaving group than halide for displacement with carbanions. ... 

As a result of the great interest in 1,2,4-triazine chemistry, much detailed data on the structure of 1,2,4-triazines have been published. The information on the structure of different types of... 

Many types of theoretical methods, ab initio molecular methods as well as semiempirical methods, have been used to calculate different aspects of 1,2,4-triazine chemistry. 

Until the first half of the 20th century, 1,3,5-triazines were only of academic interest.8 9 Subsequently, successful industrial and medicinal applications have resulted in an extensive exploration of triazine chemistry, with much of the recent published information being found in the patent literature. Several reviews and monographs have been published during the last three decades,10 -21 and there are numerous reports concerning the applications of 1,3,5-triazi-nes vide infra). 

Because of the considerable interest in 1,2,4-triazine chemistry since the 1960s, most of the structural data could be discussed in CHEC-I <84CHEC-I(3)369>. General information on the structures of different types of 1,2,4-triazines, based on x-ray crystallographic analysis, IR, UV, NMR, mass spectra, and photoelectron spectra can be found in that article. In the following sections a few additional details are presented. 

Several chapters in Advances in Heterocyclic Chemistry deal with aspects of 1,3,5-triazine chemistry reactions of ring nitrogen atoms with electrophiles <88AHC(43)I27> dihydro-l,3,5-triazines <85AHC(38)9l> halogenation of 1,3,5-triazines <93AHC(58)323> conformation of hexahydro-1,3,5-triazines <84AHC(36)160>. 

In the past decade, a shift of emphasis in 1,2,3-triazine chemistry is to be noted from preparative to theoretical work. Interest in theoretical predictions of molecular properties of the parent 1 was evident from the literature over the past 40 years and has increased recently. On the other hand, benzotriazinones of type 3 receive attention primarily for the biological activity of many derivatives, and the 3-hydroxy derivative serves as a basis for active esters as coupling reagents in peptide synthesis. Via ring-chain tautomerism, 4-hydroxy-3,4-dihydrobenzotriazines derived from 12 are opened to triazenes which show cytotoxicity. 

In the reporters opinion, 1,3,5-triazine chemistry is the most monotonous of the whole triazine family. Most of the reports of 1,3,5-triazine chemistry concern the use of their chlorine-substituted derivatives as conjugation tags due to high reactivity toward various nucleophiles. The same nucleophilic substitution reaction of suitable nucleofuges in a 1,3,5-triazine ring is also used for material functionalization, preparation of wide range derivatives for total bioscreening and other related applications. 

Another concern underlying some of the newer products has been to minimise the loss of stabiliser (and hence loss of durability under outdoor conditions), whether caused by extraction by solvents in pipes carrying fluids, or by chemical decomposition or volatility. One new Cytec UV light absorber, Cyasorb THT, combines a HALS additive with triazine chemistry. The combination was tried partly to reduce loss of additive by migration, but it was foimd to maintain the strength of polyethylene for more than twice as long as some of its competitors. 

Until recently, there were no effective, nonstaining, chemical antiozonants, since most chemical antiozonants were based upon p-phenylenediamine which severely stains rubber compounds. However, recent developments in the rubber chemicals industry have resulted in the production of a nonstaining, slightly discoloring anti-ozonant based upon triazine chemistry. This antiozonant is 2,4,6-tris-(Af-1,4-dimethyl-pentyl-p-phenylenediamino)-l,3,5-triazine (TAPDT), and the molecular stmcture is shown below. 

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