2,6-Dicyano-4-pyrone as a Novel and Multifarious Building Block for the Synthesis of 2,6-Bis(hetaryl)-4-pyrones and 2,6-Bis(hetaryl)-4-pyridinols

Abstract

In this work, a three-stage and easily scalable synthesis of 2,6-dicyano-4-pyrone (overall yield of 45%) as a new convenient building block has been developed from diethyl acetonedioxalate. It was shown that the transformation with hydroxylamine and [3 + 2]-cycloaddition, in contrast to the reactions with hydrazines, selectively proceed through the attack at the cyano groups without the pyrone ring-opening to give symmetrical and unsymmetrical pyrone-bearing heterocyclic triads containing 1,2,4- and 1,3,4-oxadiazoles as well as tetrazole moieties. The reaction of 2,6-bis­(hetaryl)-4-pyrones with ammonia afforded 2,6-bis­(hetaryl)­pyridines in 63–87% yields. The 4-pyridone/4-pyridinol tautomerism of 2,6-bis­(hetaryl)­pyridinols and the influence of the nature of adjacent azolyl moieties on this equilibrium have been discussed.

Antifungal γ‐Pyrone and Isoprenylated Cyclohexanoids from the Fungus Beenakia informis

“…This information allowed the closure of a γ‐pyrone with a quaternary hydroxylated carbon attached to one of β positions of the pyrone. Moreover, the coupling constant of 2.3 Hz between H‐5 and H‐7 is typical for this type of substructure [2] . On the other hand, a correlation between the methylene protons at δ H 2.88 and δ C 113.4 (C‐5) placed this two‐methylene chain on the other β position.…”

“…Position over, the coupling constant of 2.3 Hz between H-5 and H-7 is typical for this type of substructure. [2] On the other hand, a correlation between the methylene protons at δ The absolute configuration of the only asymmetric center was determined by electronic circular dichroism (ECD) and comparison with both TDDFT calculated enantiomers. [3] The superimposed curves are shown in Figure 3, showing the absolute configuration as S for compound 1.…”

Synthesis of 5-Aroyl-2-aryl-3-hydroxypyridin-4(1H)-ones

“…The structures of all synthesized compounds were characterized based on 1 H, 13 C NMR (see SM), and IR spectroscopy data and supported by HRMS values. Although Nunsubstituted pyridones can undergo pyridinol/pyridone tautomerism [22,23], compounds 2 and 3 exist in the pyridone form. The 1 H NMR spectra of these compounds The debenzylation of products 2a-c under the action of TMSI generated in situ in anhydrous acetonitrile from TMSCl and NaI allowed us to obtain 5-acyl-2-hetaryl substituted 3,4-HPOs 3a-c in 89-92% yields.…”

“…The structures of all synthesized compounds were characterized based on 1 H, 13 C NMR (see SM), and IR spectroscopy data and supported by HRMS values. Although N-unsubstituted pyridones can undergo pyridinol/pyridone tautomerism [22,23], compounds 2 and 3 exist in the pyridone form. The 1 H NMR spectra of these compounds display the presence of the characteristic pyridone H-6 singlet or doublet (J H-6,NH = 3.6-6.6 Hz) at δ 7.78-7.90 ppm and the downfield singlet or doublet of the NH group at δ 12.14-12.30 ppm.…”

2-Aryl-6-Polyfluoroalkyl-4-Pyrones as Promising RF-Building-Blocks: Synthesis and Application for Construction of Fluorinated Azaheterocycles

“…Mainly, pyrones are of interest as useful and versatile building-blocks for the synthesis of valuable molecules [ 6 , 7 , 8 , 9 ], including pharmaceuticals [ 10 ] and pyranic fluorophores [ 11 ]. Pyrones as polyelectrophilic substrates and cyclic enone are able to react regioselectively with nucleophiles to undergo ring-opening transformations affording azaheterocycles [ 12 , 13 , 14 , 15 , 16 ]. The formation of the product is usually very sensitive to the reaction conditions (acidity, solvent polarity, temperature) that allows divergent syntheses on the basis of 4-pyrones [ 15 , 16 ].…”