Hetaryl-substituted 1,2,4-triazines

The reaction of 1,2-dicarbonyl compounds (477) with amidrazones (478) is the best method for the synthesis of alkyl-, aryl- or hetaryl-substituted 1,2,4-triazines (481) (78HC(33)189). Mixtures result unless the dione (477) is symmetrical. 

The reaction of 1,2-dicarbonyl compounds (452) with amidrazones (453) is the best method for the synthesis of alkyl, aryl or hetaryl substituted 1,2,4-triazines (78HC(33)189, p. 195). No limitation of this synthetic principle is reported, except that it is, of course, preferable for the dione (452) to be symmetrical. The best reaction procedure is to add the dicarbonyl compound to a solution of the free amidrazone, or amidrazonium salt in the presence of one mole of base, and allow a reaction time of about 12 h. Since the first step of this reaction, i.e. condensation of the hydrazono group with one carbonyl group, is fast, while the second, i.e. condensation of the amide group with the other carbonyl, is slow, the intermediate (454) has been isolated in a few cases. This method has been used also for the synthesis of compounds containing more than one 1,2,4-triazine nucleus, and for the parent 1,2,4-triazine (1) (68CB3952). 

Organolithium derivatives of arenes and hetarenes have been shown to react smoothly with l,2,4-triazin-4-oxides 26 in the presence of acetyl chloride to give 5-aryl- or 5-hetaryl substituted 1,2,4-triazines 88, as the Sn products. In this case, aromatization of the intermediate cr -adducts 87 takes place due to O-acetylation of the 1,2,4-triazine Af-oxides and elimination of OAc as the auxiliary group (Scheme 49). 

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See also in sourсe #XX -- [ ]

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