2.4.6- Trialkyl-l,3,5-triazines

Triaryl-1,3,5-triazines are more readily prepared than are the alkyl derivatives (see Section 2.20.4). In general, the compounds are stable, and 2,4,6-triphenyl-l,3,5-triazine, for example, can be distilled at ca. 350 °C without decomposition. These compounds undergo similar ring-opening reactions to the 2,4,6-trialkyl-l,3,5-triazines, but the reaction requires even more vigorous conditions (see Section 2.20.3.2) <59HC(l3)l, p.178). 

A variety of imino derivatives has been used in the synthesis of 1,3,5-triazine (Scheme 85) (B-61MI22000, p. 680). The trimerization of the imidates is the most valuable of these routes to 1,3,5-triazine. Imidates can be considered as activated nitriles, and cyclotrimerize more readily than do the corresponding nitriles. The symmetrical 2,4,6-trialkyl-l,3,5-triazines are easily formed (Table 15), although large alkyl substituents may give rise to steric hindrance (61JOC2778). The mechanism is shown in Scheme 86. 

The a-hydrogens of 2,4,6-trialkyl-l,3,5-triazines are readily chlorinated or brominated in the presence of acid. The reaction is believed to occur via an ionic mechanism. The final products using an excess of chlorine or bromine are strongly dependent on the reaction conditions used (Scheme 19) (64JOC1527). 2-Alkyl-1,2-dihydro-l,3,5-triazines (36) may be rearranged in good yields to pyrimidines (Scheme 20) (79TL1241). 

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See also in sourсe #XX -- [ ]

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