Regioselective 3-Nitration of Flavones: A New Synthesis of 3-Nitro- and 3-Aminoflavones

Abstract

A new, general, and regioselective method for the 3-nitration of flavones have been developed. The nitration reaction is solvent dependent, proceeds via a nitro radical pathway, and the corresponding 3-nitroflavones have been obtained in moderate to very good yields (up to 81%). The reduction of 3-nitroflavones allowed the preparation of the corresponding 3-aminoflavones in very good yields (up to 96%).

Structure–Activity Relationship Study on Col-003, a Protein–Protein Interaction Inhibitor between Collagen and Hsp47

“…Similarly, reactions of 5-bromo-3-fluorosalicylaldehyde (3b) 16) and 5-bromo-3-chlorosalicylaldehyde (3c) 17) with benzylzinc reagents 4A-C successfully provided the corresponding analogues 2bA-2bC and 2cA-2cC in moderate to good yields (entries 4-9). Alter-natively, all the reactions of 3,5-dibromosalicylaldehyde (3d) 18) and 5-bromo-3-nitrosalicylaldehyde (3e) 19) with 4A-4C resulted in a complex mixture (entries 10-15), probably because 3d has two reactive bromide atoms, which might have made the regioselective reaction difficult, and 3e would undergo nucleophilic addition of the organozinc reagents to an aldehyde moiety activated by an adjacent highly electron-withdrawing NO 2 group.…”

“…Next, we employed ortho-bromination and ortho-nitration of phenols in the coupling products 2aA-2aC. Treatment of 2aA-2cA with NBS/MeCN or NH 4 NO 3 /trifluoroacetic anhydride (TFAA) 20) provided the brominated analogues 2dA-2dC or nitrated analogues 2eA-2eC, respectively ( Table 2).…”

Green Electrochemical Synthesis of the 6,7-Dihydroxycoumarin Derivative and Electronitration of Some Flavonoids: Biological Evaluation and Molecular Docking

“…Among the most frequently used processes for the synthesis of coumarin-based compounds, the intramolecular cyclization reaction via chemical oxidants is a favorite route for the creation of the C–O bond . To reduce the use of chemical oxidants, an electron transfer process accompanied with cyclization provides an interesting opportunity as a green and metal/oxidant-free method for the production of pharmacologically important coumarin analogues. − Nitroaromatic compounds have been used as a chemical feedstock for manufacturing a variety of materials, including explosives, fertilizers, drugs, perfumes, dyes, plastics, energetic materials, and pesticides. − Nitroflavone derivatives demonstrated a variety of biological features such as antiproliferative, antitumor, neuroprotective, and anxiolytic activities …”

“…16−18 Nitroflavone derivatives demonstrated a variety of biological features such as antiproliferative, antitumor, neuroprotective, and anxiolytic activities. 19 The disadvantages of chemical methods and advantages of electrochemical methods, such as ambient temperature and pressure, no toxic catalysts, high yield, uses green solvent, one pot, and facile, promoted us to synthesize novel nitroaromatic compounds via the electrochemical method. 20 (E)-3-(3,4-Dihydroxyphenyl)acrylic acid (3,4-DHPA), quercetin (QE), and rutin are phenolic acid and polyphenol compounds that can be easily oxidized electrochemically to o-benzoquinones in the mild media.…”