Synthesis of Flavones from the Hypervalent Iodine Oxidation of Flavanones Using [Hydroxy(tosyloxy)iodo]benzene in Methanol

Prakash, Om; Pahuja, S.; Moriarty, Robert M.

doi:10.1080/00397919008052857

Cited by 30 publications

(5 citation statements)

References 10 publications

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“…At the outset of this project we undertook a comprehensive survey of the literature examples for flavanone to isoflavone oxidative rearrangements (reaction 7 → 8 in Scheme ). While some groups report the selective formation of isoflavones 8 upon treatment of flavanones 7 with either Tl(III)-salts − or hypervalent iodine compounds, , others report that benzofurans 13 − or flavones 14 , are the main or exclusive products, or that mixtures of these three products were obtained. The formation of all three types of oxidative rearrangement products 8 , 13 , and 14 can be explained from a common intermediate 15 , which is formed by electrophilic iodination of flavanone 7 with a hypervalent iodine reagent Ph–IX 2 at the α-position of the carbonyl group .…”

Section: Introductionmentioning

confidence: 99%

Scope and Applications of 2,3-Oxidative Aryl Rearrangements for the Synthesis of Isoflavone Natural Products

2021

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The reaction of flavanones with hypervalent iodine reagents was investigated with a view to the synthesis of naturally occurring isoflavones. In contrast to several previous reports in the literature, we did not observe the formation of any benzofurans via a ring contraction pathway, but could isolate only isoflavones, resulting from an oxidative 2,3aryl rearrangement, and flavones, resulting from an oxidation of the flavanones. Although the 2,3-oxidative rearrangement allows a synthetically useful approach toward some isoflavone natural products due to the convenient accessibility of the required starting materials, the overall synthetic utility and generality of the reaction appear to be more limited than previous literature reports suggest.

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Section: Introductionmentioning

confidence: 99%

Scope and Applications of 2,3-Oxidative Aryl Rearrangements for the Synthesis of Isoflavone Natural Products

2021

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“…13 The change of the solvent to methanol resulted in a dramatic shift as flavone (3c) became the major product, accompanied by some cis-3-methoxyflavanone and methyl 2-phenyl-2,3-dihydrobenzofuran-3-carboxylate. 14 The oxidative rearrangement of flavanone (1c)…”

Section: Methodsmentioning

confidence: 99%

Microwave-induced, solvent-free transformations of benzoheteracyclanones by HTIB (Koser`s reagent)

Patonay¹,

Lévai²,

Rimán³

et al. 2004

Arkivoc

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The microwave-activated reactions of [hydroxy(tosyloxy)iodo]benzene (HTIB) with various chromanones, thiochromanones and dihydroquinolones under solvent-free conditions have been studied. In addition to the common dehydrogenation reaction, 2,3-migration also has been observed in the case of flavanone and 2,2-disubstituted chromanones. 3-Tosyloxychromanones were isolated from the reaction of chromanone and 2-methylchromanone for the first time. Substrates with nucleophilic heteroatoms such as thiochromanones and 2-phenyl-2,3-dihydro-4-quinolone reacted by electrophilic attack of the heteroatom.

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“…In this synthesis the prenyl substituent was introduced after the oxidative rearrangement through a Pd-catalyzed coupling . One reason for the restricted utilization of the oxidative rearrangement method could be the confusing and sometimes contradictory literature precedence: isoflavones, flavones, and benzofurans or mixtures of these products have been reported to arise from the reaction of flavanones with hypervalent iodine reagents. − A plausible mechanism for the formation of all three types of products is shown in Scheme for the reaction of an unsubstituted flavanone A with the hypervalent iodine reagent [bis(trifluoroacetoxy)iodo]benzene (BTI). , The initial step is an electrophilic iodination of A at C-3 that presumably proceeds via the enol B . The 3-iodinated product C is the central intermediate for all possible products: isoflavones are formed via migration of the C-2-aryl substituent with intramolecular substitution of the iodo substituent and deprotonation at C-3 (black arrows), flavones result from β-elimination (blue arrow), and benzofurans result from a ring contraction (red arrow) and nucleophilic trapping of the oxocarbocation ( G ) with MeOH.…”

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confidence: 99%

Total Syntheses of Prenylated Isoflavones from Erythrina sacleuxii and Their Antibacterial Activity: 5-Deoxy-3′-prenylbiochanin A and Erysubin F

et al. 2020

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The prenylated isoflavones 5-deoxyprenylbiochanin A (7-hydroxy-4′-methoxy-3′-prenylisoflavone) and erysubin F (7,4′-dihydroxy-8,3′-diprenylisoflavone) were synthesized for the first time, starting from mono- or di-O-allylated chalcones, and the structure of 5-deoxy-3′-prenylbiochanin A was corroborated by single-crystal X-ray diffraction analysis. Flavanones are key intermediates in the synthesis. Their reaction with hypervalent iodine reagents affords isoflavones via a 2,3-oxidative rearrangement and the corresponding flavone isomers via 2,3-dehydrogenation. This enabled a synthesis of 7,4′-dihydroxy-8,3′-diprenylflavone, a non-natural regioisomer of erysubin F. Erysubin F (8), 7,4′-dihydroxy-8,3′-diprenylflavone (27), and 5-deoxy-3′-prenylbiochanin A (7) were tested against three bacterial strains and one fungal pathogen. All three compounds are inactive against Salmonella enterica subsp. enterica (NCTC 13349), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028), with MIC values greater than 80.0 μM. The diprenylated natural product erysubin F (8) and its flavone isomer 7,4′-dihydroxy-8,3′-diprenylflavone (27) show in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA, ATCC 43300) at MIC values of 15.4 and 20.5 μM, respectively. In contrast, the monoprenylated 5-deoxy-3′-prenylbiochanin A (7) is inactive against this MRSA strain.

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Synthesis of Flavones from the Hypervalent Iodine Oxidation of Flavanones Using [Hydroxy(tosyloxy)iodo]benzene in Methanol

Cited by 30 publications

References 10 publications

Scope and Applications of 2,3-Oxidative Aryl Rearrangements for the Synthesis of Isoflavone Natural Products

Scope and Applications of 2,3-Oxidative Aryl Rearrangements for the Synthesis of Isoflavone Natural Products

Microwave-induced, solvent-free transformations of benzoheteracyclanones by HTIB (Koser`s reagent)

Total Syntheses of Prenylated Isoflavones from Erythrina sacleuxii and Their Antibacterial Activity: 5-Deoxy-3′-prenylbiochanin A and Erysubin F

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