Synthesis and study of azide-tetrazole tautomerism in 2-azido-6-phenylpyrimidin-4(3H)-one and 2-azido-4-chloro-6-phenylpyrimidine

Aleksandrova, N. V.; Николаенкова, Елена Б.; Gatilov, Yu. V.; Polovyanenko, Dmitriy N.; Mamatyuk, V. I.; Krivopalov, V. P.

doi:10.1007/s11172-022-3529-8

Cited by 2 publications

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“…From the synthesis perspective, heterocycles with an azido-azomethine structural entity are interesting due to their intrinsic dynamic azide-tetrazole tautomeric equilibrium in the solution phase (Figure 1a) [8][9][10][11][12][13][14][15] alongside rich azide functional group chemistry [16].…”

Section: Introductionmentioning

confidence: 99%

SnAr Reactions of 2,4-Diazidopyrido[3,2-d]pyrimidine and Azide-Tetrazole Equilibrium Studies of the Obtained 5-Substituted Tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines

et al. 2022

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A straightforward method for the synthesis of 5-substituted tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines from 2,4-diazidopyrido[3,2-d]pyrimidine in SNAr reactions with N-, O-, and S- nucleophiles has been developed. The various N- and S-substituted products were obtained with yields from 47% to 98%, but the substitution with O-nucleophiles gave lower yields (20–32%). Furthermore, the fused tetrazolo[1,5-a]pyrimidine derivatives can be regarded as 2-azidopyrimidines and functionalized in copper(I)-catalyzed azide-alkyne dipolar cycloaddition (CuAAC) and Staudinger reactions due to the presence of a sufficient concentration of the reactive azide tautomer in solution. In total, seven products were fully characterized by their single crystal X-ray studies, while five of them were representatives of the tetrazolo[1,5-a]pyrido[2,3-e]pyrimidine heterocyclic system. Equilibrium constants and thermodynamic values were determined using variable temperature 1H NMR and are in agreement of favoring the tetrazole tautomeric form (ΔG298 = −3.33 to −7.52 (kJ/mol), ΔH = −19.92 to −48.02 (kJ/mol) and ΔS = −43.74 to −143.27 (J/mol·K)). The key starting material 2,4-diazidopyrido[3,2-d]pyrimidine presents a high degree of tautomerization in different solvents.

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