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Study of an efficient conversion of 1,3-dimethyl-5-(Arylazo)-6-Amino-Uracils to 1,3-dimethyl-8-(Aryl)-Azapurin-2,6-Diones
D. Debnath, A. Purkayastha, A. Kirillov, , T.K. Misra
Published in Elsevier B.V.
Volume: 1150
Pages: 118 - 126
6-Aminouracils have extensively been used as precursors for synthesizing numerous uracil derivatives of biological and pharmaceutical significance. This study describes an application of 1,3-dimethyl-5-(arylazo)-6-aminouracils (Uazo: Uazo1-Uazo4, precursors) for an efficient synthesis of a series of 8-substituted-azapurins (AP), namely 1,3-dimethyl-8-(aryl)-azapurin-2,6-diones (aryl = p-HC6H4 (AP1), -MeC6H4 (AP2), –ClC6H4 (AP3), and –SO2NH2C6H4 (AP4)) following an oxidation method in the presence of copper (II) nitrate and in alkaline medium. The obtained compounds were isolated in good yields as crystalline air-stable products and have been fully characterized in the solution by UV–vis and NMR spectroscopy, as well as in the solid state by FT-IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction (for AP2 and AP4). UV–vis study evidences that the conversion of the 6-aminouracil precursors occurs via an intermediate, Cu(II)-complex and a plausible mechanism for the formation of AP1-AP4 has been proposed. Unlike AP2 the crystal structure of AP4 reveals the formation of interdigitated 1D H-bonded chains that has been topologically classified within the 2C1 type. The 1H NMR spectra of the products have proton signals that completely devoid of hydrazone (–NH–) and imine (=NH) signals of their parent Uazo derivatives, thus confirming their full conversion and a stability of the AP1-AP4 in solution. The excitation and emission spectra of AP1-AP4 were also recorded in solution, revealing electronic transitions between similar vibrational energy levels of S0 (singlet ground state) and S1 (singlet first excited state). © 2017 Elsevier B.V.
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Published in Elsevier B.V.
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