Depending on the reaction conditions, acylation of unsubstituted 3,5-diamino-1,2,4-triazole leads to the formation of acylation products at both the ring N (1) atom and at the exocyclic amino groups [1][2][3][4]. The direction of acylation of 3,5-diamino-1-R-1,2,4-triazole 1 has not been established precisely up to the present time. It has been shown that brief heating of 3,5-diamino-1-phenyl-1,2,4-triazole (1a ) with acetic anhydride leads to the formation of a monoacetyl derivative, but refluxing in an excess of anhydride leads to the formation of a diacetyl derivative, the structures of which were not determined [5]. The product of the interaction of 1a with acetoacetic ester was assigned the structure of 1-acetoacetyl-3,5-diimino-2-phenyl-1,2,4-triazole [6], but with cyanates and thiocyanates the carbamoyl and thiocarbamoyl derivatives at one of the exocyclic amino groups were formed [7]. The problem of the reaction direction remained open.The aim of the present work is the determination of the direction of acylation and sulfonation reactions of 3,5-diamino-1-R-1,2,4-triazoles 1a,b.It was established that the interaction of compounds 1a,b with an equimolar quantity of anhydrides 2a-c, carboxylic acid chlorides 2d-f,i, and sulfonyl chlorides 2g,h proceeds regioselectively and gives 3-acylamino-5-amino-1-R-1,2,4-triazoles 3a-f,i,j and 5-amino-3-sulfonylamino-1-R-1,2,4-triazoles 3g,h,k in good yield (Scheme 1, Table 1).According to the data of [8,9] the 1 H NMR spectra of 3,5-diamino-1-R-1,2,4-triazoles in DMSO-d 6 have broad discernible singlets for the protons of the 3-NH 2 and 5-NH 2 groups in the region of 5 and 6 ppm respectively. The chemical shifts of 5.08 and 4.75 (3-NH 2 ), 6.15 and 6.05 ppm (5-NH 2 ) correspond to the protons of the amino groups of compounds 1a,b. In the 1 H NMR spectra of compounds 3a-k the 3-NH 2 signal has disappeared, but a signal for an amide proton appears at 9.8-12.5 ppm. The singlet of the 5-NH 2 protons is displaced a little towards low field and appears in the range 6.25-6.60 ppm (Table 2). These values of the __________________________________________________________________________________________ South
structural analysis, structure.Alkylation of C-amino-1,2,4-triazoles by alkyl halides and alkyl sulfates usually occurs at the nitrogen atom of the heterocycle to give the aminotriazoles or iminotriazolines substituted in the ring [1][2][3][4][5][6]. Such an alkylation route is typical of the majority of amino azoles and azines in which the amino group is conjugated with the pyridine type nitrogen atom of the heterocycle [7]. Thus alkylamino-1,2,4-triazoles are usually prepared by cyclization of alkyl substituted acyclic precursors [3, 8-10], hydrogenation of arylideneamino-or acylamino-1,2,4-triazoles [11][12][13], or ammonolysis of halo-substituted 1,2,4-triazoles [4].We have proposed that the alkylation reaction route for the amino-1,2,4-triazoles can be altered by initial acylation or sulfonation of the amino group. In the presence of base an electron acceptor acyl (sulfonyl) group can facilitate deprotonation and give a conjugated N-anion, alkylation of which can give the N-acyl(sulfonyl)-N-alkylamino-1,2,4-triazoles.
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