Synthesis of 2,4-Diamino-6-arylpyridine-3,5-dicarbonitriles and Study of Their Optical Properties
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Synthesis of 2,4-Diamino-6-arylpyridine-3,5-dicarbonitriles and Study of Their Optical Properties I. N. Bardasova,*, A. Yu. Alekseevaa, D. L. Mikhailova, A. I. Ershovaa, and O. V. Ershova a
Ul’yanov Chuvash State University, Cheboksary, 428015 Russia *e-mail: [email protected]
Received April 10, 2020; revised April 24, 2020; accepted April 30, 2020
Abstract—2,4-Diamino-6-arylpyridine-3,5-dicarbonitriles were synthesized by the nucleophilic substitution of bromine in 4-amino-2-bromo-6-arylpyridine-3,5-dicarbonitriles. The optical properties of the synthesized compounds were studied to show that they fluoresce in solution and in the solid state in the violet region of the spectrum. Keywords: pyridines, aminopyridines, nucleophilic substitution, fluorescence
DOI: 10.1134/S1070428020080266 2- and 4-Aminopyridines are either used as precursors of biologically active compounds or exhibit diverse biological activities in themselves. For example, we can mention derivatives that act as inhibitors of c-Jun-N-terminal kinases (JNK) [1], mitogen-activated protein kinase-activated protein kinase 2 (MK-2) [2], DNA ligases [3], and tyrosine kinase [4] and also used as anticancer drugs [5]. Corrosion inhibitors on the basis of pyran-annulated 2,4-diaminopyridines can also be mentioned [6]. Multicomponent reactions involving malononitrile dimer are among the most common method of synthesis of 2,4-diaminopyridines annulated to the pyran, pyridine, or other moieties [6–16]. Selective introduction of amino groups with the aim of preparation of 2,4-diaminopyridines of desired structure can be accomplished via nucleophilic substitution of the halogen atom [17–20] and reduction
of the azido group [21, 22] in the corresponding halo or azidopyridines. In the present work we synthesized previously unknown 2,4-diamino-6-arylpyridine-3,5-dicarbonitriles 1 and studied their optical properties. In [23] we showed that the halogen atom in 4-amino-2bromo-6-arylpyridine-3,5-dicarbonitriles 2 is easily replaced by primary and secondary amines to form the corresponding 2-alkylaminopyridines. Continuing this research we found that diaminopyridines 1 does not form under such conditions. As know from [19, 24], ammonia substitution for halogen occurs exclusively under harsh conditions. Optimizing conditions for synthesis we found that the reaction of 4-amino2-bromo-6-arylpyridine-3,5-dicarbonitriles 2 with aqueous ammonia in an autoclave at 110°C for 6 h gives rise to 2,4-diamino-6-arylpyridine-3,5-dicarbonitriles 1a–1f in yields of 73–85% (Scheme 1).
Scheme 1.
1501
1502
BARDASOV et al.
Table 1. Optical properties of compounds 1 Compound λabs, nm no.
a
εmax
λfluor, nm
Λfluor.solid, nma
1a
323
7960
438
405
1b
297, 326
11435, 8876
438
430
1c
298, 324
7979, 6735
436
–
1d
320
6043
435
–
1e
322
7112
439
–
1f
307
17505
435
432
Solid-state fluorescence emission maximum.
The 1H NMR spectra contain signals of the aryl substituent and two amino groups as broadened singlets at 7.10–7.53 ppm. The IR
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