Reactions of 2-Mono- and 2,6-Disubstituted 4-Pyrones with Phenylhydrazine as General Method for the Synthesis of 3-(N-Phenylpyrazolyl)Indoles

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

“…Phenylhydrazine reacted with pyrone 5a regioselectively attacking with the amino group at the C-2 and C-4 positions to give pyrazole 9 . The structure of pyrazole 9 was assigned based on NMR spectra according to the literature data [ 16 , 34 ].…”

“…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 ].…”

“…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 ].…”

“…To date considerable attention has been focused on 4-pyrones bearing the electron-withdrawing R F group, which demonstrate higher reactivity with high chemoselectivity of processes compared to non-fluorinated analogs [ 17 , 18 ]. The ring-opening reactions of 2-R F -4-pyrones can be applied for the preparation of a wide range of trifluoromethylated azaheterocycles, such as indoles, regioisomeric pyrazoles, pyridines, benzodiazepines etc., [ 14 , 16 , 17 , 18 ].…”

Oxidative Ring-Opening Transformation of 5-Acyl-4-pyrones as an Approach for the Tunable Synthesis of Hydroxylated Pyrones and Furans

“…Pyrones and furans are important classes of oxygen-containing heterocyclic compounds that are widely distributed in nature, exhibit various beneficial biological activities (antitumor, antioxidant, antiviral, antifungal, and others), and are used in pharmaceuticals , and materials chemistry (Figure ). These heterocycles demonstrate a multifarious reactivity that made them convenient building blocks for the organic synthesis of complex molecules via various transformations, , including cycloadditions and ring-opening transformations . Also, it is important to note that hydroxylated 4-pyrones are widely used as chelating agents and fluorescent labels …”