77202-09-6

Radical nucleophilic carbamoylation was carried out to various 1,2,3-triazine derivatives.In the case of parent triazines as substrates, Minisci's system was not effective, and in the absence of acid, a small ammount of radical adduct was obtained.Triazinium dicyanomethylides reacted with carbamoyl radical to give 5- carbamoyl triazines in good yields.Other 1,2,3-triazine derivatives were also investigated.

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Reactions of N-aminopyrazoles with halogenating reagents (Cl2, Br2, I2, BrCl, ICl, IBr, N-chlorosuccinimide, and N-bromosuccinimide) were examined.Some of these reagents preferentially lead to oxidation of the amino group to give the corresponding 1,2,3-triazines as major products, while others mainly gave either or both of 1-amino-4-halopyrazoles and 5-halo-1,2,3-triazines as the result of halogenation of the 4-position of the pyrazole ring prior to the oxidation of the amino group.In some cases, the oxidation of the amino group and the halogenation of the pyrazole ring proceeded concurrently to form not only the unhalogenated triazines but also the 1-amino-4-halopyrazoles and the 5-halotriazines.Various reagents and reaction conditions were explored to utilize the reaction for the synthesis of halogenated and unhalogenated 1,2,3-triazines.Keywords - 1,2,3-triazine; halo-1,2,3-triazine; pyrazole; 1-aminopyrazole; 1-aminohalopyrazole; synthesis; oxidation; halogenation; ring expansion

2,5-Dihydro-1,2,3-triazines were oxidized by m-chloroperbenzoic acid to give only 1,2,3-triazine 2-oxides, while the oxidation of 1,2,3-triazines yielded the mixtures of 1- and 2-oxides.In case of adopting 2-methyl-2,5-dihydro-1,2,3-triazines as starting materials, 2-methyltriazoles and 2,5-dihydro-5-oxo-1,2,3-triazine were obtained.

Unsubstituted and various substituted monocyclic 1,2,3-triazines were synthesized from 1-aminopyrazoles by oxidation with lead tetraacetate, lead dioxide-CF3CO2H, and/or nickel peroxide-AcOH.

Oxidation of the N-aminopyrazoles 4a-i affords the 1,2,3-triazines 5a-i.Spectra and reactions - such as oxidation, reduction, and cycloaddition reactions - of some 1,2,3-triazines 5 are described.The X-ray analysis of 5a is presented.

Reduction of 4,6-disubstituted 1,2,3-triazine 2-oxides with sodium borohydride afforded the corresponding 1,4,5,6-tetrahydro-1,2,3-triazine 2-oxides as main products.The mechanism was examined using NaBH4 in CH3OD and NaBD4 in CH3OH.

Alkyl substituted monocyclic 1,2,3-triazines and their 1- and 2-oxides have been synthesized; catalytic reduction (on Pd-C) of the triazines afforded their 2,5-dihydro compounds.