Preparation of Halogen‐Containing 4H‐Pyrido[e][1,3]oxazin‐4‐ones and Their Transformation into 2‐Hydroxypyridinyl‐Substituted 1,2,4‐Oxadiazoles and 1,2,4‐Triazoles

Abstract

A complete study on the preparation of original halogen‐containing 4H‐pyrido[e][1,3]oxazin‐4‐ones and their transformation into 1,2,4‐oxadiazoles and 1,2,4‐triazoles is presented. Starting from pyridyl‐imide sodium salts, the efficiency of the intramolecular O‐arylation was studied on three series of compounds, with different fluoro‐, chloro‐, and bromophenyl substituents at the C‐2 position. The final halogenated compounds are of interest as new synthons for future functionalisation. We also present the discovery of a new, rapid, and complementary access to 2‐substituted 4H‐benzo[e][1,3]oxazinones. Finally, the one‐step transformation of some of these pyrido‐oxazinones into the corresponding hydroxypyridyl‐substituted 1,2,4‐oxadiazoles and 1,2,4‐triazoles was explored, and the regioselectivity of the reaction was proved by X‐ray crystallography.

In silico design of bio-marker detection fluorescent probes

“…We compared our calculated results with the experimental data. 24 The reader can refer to Fig. S2, S3 and Table S3 in the ESI† for details.…”

“…Some of us have recently reported the synthesis of 3-hydroxypyridyl-1,2,4-triazoles with interesting fluorescent properties such as large Stokes shift and dual emission. 23–25 Throughout our research, we computationally engineer the Stokes shift and emission wavelength of a set of molecules derived from 2-hydroxyphenyl-1,2,4-triazole (referred to as 1 in Fig. 1).…”

‘Heteroaromatic Rings of the Future’: Exploration of Unconquered Chemical Space

“…Exposure of 4H-pyrido [1,3]oxazin-4-ones 3 to phenylhydrazine or hydroxylamine led, respectively, to the corresponding hydroxypyridine-substituted 1,2,4-triazoles 4 and 1,2,4-oxadiazoles 5 in good yields via an ANRORC type mechanism (Scheme 2). 13 Efficient access to 2-hydroxypyridyl-substituted 1,3,5-triazines 6 was also developed from a wide panel of pyridoxazinones and the corresponding amidines in one step under microwave assisted reaction conditions in good to excellent yields. 14 In the meantime, we have developed Pd(II)-catalyzed cross-coupling reactions on 2-substituted 4H-pyrido [1,3]oxazin-4-ones 3 to access polyfunctionalized precursors with extended π-conjugation for further applications as fluorescent materials.…”

“…38 The pyridinone 39 was obtained from 2-methoxypyridine 44 by a subsequent demethylation step using sodium iodide and TMSCl in boiling acetonitrile (Scheme 12). Thanks to 1 H, 13 C, and 15 N NMR experiments at ambient and low temperatures, all…”

Síntese, funcionalização e prospecção biológica de fragmentos heterocíclicos baseados em núcleos heteroaromáticos subexplorados

“…Apesar de a maioria de fragmentos moleculares apresentarem baixa atividade biológica e necessitarem de um processo de otimização estrutural, alguns compostos (Tsikouris et al, 2008;Silva Junior et al, 2016), e outros 6 foram construídos já com algum substituinte no anel [1 (Slowinski et al, 2013;Le Falher et al, 2015); 5 (Kelemen et al, 2016); 6 (Csimbók et al, 2016); 11 (Kondo et al, 2011); 12 (Sparey et al, 2008;Nayak et al, (Hatherley et al, 1993), por ter característica mais aromática (Galvão et al, 2013). No entanto, a posição de um nitrogênio extra no anel piridona, influência diretamente na forma tautomérica, sendo que, no caso da 3-piridazinona, a forma ceto é a única encontrada (Lapinski et al, 1992;Graff e Dobrowolski, 2013).…”