Novel Synthesis of Flavones by Regioselective Cyclization of 1‐(2‐Hydroxyphenyl)‐3‐phenyl‐2‐propyn‐1‐ones Derived from 2‐Hydroxybenzoic Acids

Lee, Jae-In

doi:10.1002/bkcs.11134

Cited by 8 publications

(5 citation statements)

References 27 publications

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“…The use of triflic acid (1 equiv) in 1,2‐dichloroethane or 4‐(dimethylamino)pyridine (0.1 equiv) in DMF on the cyclization of o ‐(alkynon‐1‐yl)phenols predominantly induced 6‐ endo cyclization to provide flavones. The 1,4–addition of diethylamine (10 equiv) to O ‐TBS protected alkynones in EtOH or sodium 2‐pyridinethiolate (1 equiv) to o ‐(alkynon‐1‐yl)phenols in THF afforded the corresponding enaminoketone or β‐(2‐pyridylthio)phenoxide intermediates, respectively, which underwent intramolecular cyclization to give flavones at reflux temperature. The treatment of o ‐alkynoylphenyl acetates with CH 3 OK (2.5 equiv) using 18‐crown‐6 (2.5 equiv) in THF provided the corresponding phenoxide intermediates, which underwent cyclization and subsequent leaving of methoxy group to give flavones …”

Section: Methodsmentioning

confidence: 99%

“…As an extension of our studies on the synthesis of flavones, we herein report that flavones can be synthesized by regioselective cyclization of o ‐(alkynon‐1‐yl)phenols using 0.05 equiv of thallium(III) p ‐tosylate in CH 3 OH. Thallium(III) p ‐tosylate has been utilized for the conversion of flavanones to isoflavones via oxidative 2,3‐aryl rearrangement, but it has not been used for the cyclization of o ‐(alkynon‐1‐yl)phenols…”

Section: Methodsmentioning

confidence: 99%

“…N ‐Methoxy‐ N ‐methyl o ‐hydroxybenzamides ( 2a ‐ e ) as precursors of o ‐(alkynon‐1‐yl)phenols were prepared by the slow addition of 3 equiv of isopropylmagnesium chloride to a slurry solution of methyl o ‐hydroxybenzoates ( 1a ‐ e ) and Me(OMe)NH 2 Cl in THF in 80–92% yields according to our previous methods (Scheme ). The addition of arylethynyllithiums to a pretreated solution of 2a ‐ e with lithium diisopropylamide in THF afforded o ‐(alkynon‐1‐yl)phenols ( 3 ) in 71–92% yields after the usual acidic work‐up and chromatographic separation.…”

Section: Methodsmentioning

confidence: 99%

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Synthesis of Flavones by Thallium(III) p‐tosylate‐catalyzed Regioselective Cyclization of o‐(Alkynon‐1‐yl)phenols

Lee

Kim

2018

Bulletin Korean Chem Soc

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Flavones are important classes of flavonoids and have been isolated from a wide variety of plants, fruits, and vegetables. 1 They have attracted considerable interests due to their diverse pharmacological properties on human health, including antioxidant, anti-inflammatory, anticancer, antifungal, and antimicrobial activities. 2 A number of methods for synthesizing flavones have been reported, 3 which can be mainly classified as cyclodehydration of 1-(2-hydroxyphenyl)-3-phenyl-1,3-propanediones, 4 oxidative cyclization of 2 0 -hydroxychalcones, 5 and carbonylative cyclization of o-iodophenols with arylacetylenes in the presence of palladium catalyst. 6 Recently, the cyclization of o-(alkynon-1-yl)phenols has been investigated as a convenient method of flavone synthesis. However, the intramolecular cyclization of o-(alkynon-1-yl)phenols produced not only flavones via 6-endo-digonal cyclization (path a) but also aurones via 5-exo-digonal cyclization (path b) and the ratio of products was highly dependent on the kinds of reagents and solvents (Scheme 1).The reaction of o-(alkynon-1-yl)phenols and K 2 CO 3 (0.2 equiv) in refluxing acetone afforded products of both 6-endo and 5-exo cyclization as the major of 6-endo mode, while 5-exo cyclization became enhanced when ethanol was used as protic media. 7 The use of triflic acid 8 (1 equiv) in 1,2-dichloroethane or 4-(dimethylamino)pyridine 9 (0.1 equiv) in DMF on the cyclization of o-(alkynon-1-yl)phenols predominantly induced 6-endo cyclization to provide flavones. The 1,4-addition of diethylamine 10 (10 equiv) to O-TBS protected alkynones in EtOH or sodium 2-pyridinethiolate 11 (1 equiv) to o-(alkynon-1-yl)phenols in THF afforded the corresponding enaminoketone or β-(2-pyridylthio)phenoxide intermediates, respectively, which underwent intramolecular cyclization to give flavones at reflux temperature. The treatment of oalkynoylphenyl acetates with CH 3 OK (2.5 equiv) using 18-crown-6 (2.5 equiv) in THF provided the corresponding phenoxide intermediates, which underwent cyclization and subsequent leaving of methoxy group to give flavones. 12 However, the use of PBu 3 13 (0.05 equiv) in EtOH or Cs 2 CO 3 14 (3 equiv) in acetone on the cyclization of o-(alkynon-1-yl)phenols induced the 5-exo cyclization with a high regioselectivity to give aurones. The treatment of o-(alkynon-1-yl)phenols with AgNO 3 15 (0.3 equiv) in CH 3 OH or AgOAc 16 (0.03 equiv) in DMF also induced high 5-exo cyclization via dual-coordination process to give aurones. The reaction of o-(alkynon-1-yl)phenols and sodium 2-pyridyloxide (0.1 equiv) in THF provided the corresponding sodium phenoxides, which underwent 5-exo cyclization kinetically to give aurones after protonation by 2-PyOH. 17 As an extension of our studies on the synthesis of flavones, 11,18 we herein report that flavones can be synthesized by regioselective cyclization of o-(alkynon-1-yl)phenols using 0.05 equiv of thallium(III) p-tosylate in CH 3 OH. Thallium(III) p-tosylate has been utilized for the conversion of flavanones to isoflavo...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Synthesis of Flavones by Thallium(III) p‐tosylate‐catalyzed Regioselective Cyclization of o‐(Alkynon‐1‐yl)phenols

Lee

Kim

2018

Bulletin Korean Chem Soc

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“…The successive acyl substitution of 10 pretreated with LDA by arylethynyllithiums gave the corresponding 2‐(alkynon‐1‐yl)phenols ( 11 ) (Scheme 8). 21 …”

Section: Preparation From Carboxylic Estersmentioning

confidence: 99%

Synthetic Approaches to N‐Methoxy‐N‐methylamides

Lee

Park

2021

Bulletin Korean Chem Soc

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N-Methoxy-N-methylamides were prepared by the acylation of acid halides, acyl cyanides, esters, lactones, activated amides, and mesyl carboxylates with N,O-dimethylhydroxylamine hydrochloride. The reaction of carboxylic acids with alkyl chloroformates, phosphonate reagents, or coupling agents afforded the activated esters, which were converted to N-methoxy-N-methylamides by (CH 3 O)NHCH 3 . N-Methoxy-N-methylamides were also prepared by the oxidative amidation of benzyl alcohols and palladiumcatalyzed aminocarbonylation of organoboronic acids or aryl halides with (CH 3 O)NHCH 3 under CO equivalents. Furthermore, N-methoxy-N-methylamides were produced by the selective substitution of N,O-dimethylcarbamoylation agents with organometallic reagents.

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“…General approaches to flavone syntheses: (A) from chalcones (following Kostanecki's synthesis); (B) from 1,3-diaryl propandiones (following Kostanecki—Robinson—Venkataraman ideas); (C) from phenylalkenyl ketones, according to Lee (2017). …”

Section: Quest For the Fisetin Apimentioning

confidence: 99%

New Perspectives for Fisetin

Grynkiewicz

Demchuk

2019

Front. Chem.

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Fisetin is a flavonol that shares distinct antioxidant properties with a plethora of other plant polyphenols. Additionally, it exhibits a specific biological activity of considerable interest as regards the protection of functional macromolecules against stress which results in the sustenance of normal cells cytoprotection. Moreover, it shows potential as an anti-inflammatory, chemopreventive, chemotherapeutic and recently also senotherapeutic agent. In view of its prospective applications in healthcare and likely demand for fisetin, methods for its preparation and their suitability for pharmaceutical use are discussed herein.

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Novel Synthesis of Flavones by Regioselective Cyclization of 1‐(2‐Hydroxyphenyl)‐3‐phenyl‐2‐propyn‐1‐ones Derived from 2‐Hydroxybenzoic Acids

Cited by 8 publications

References 27 publications

Synthesis of Flavones by Thallium(III) p‐tosylate‐catalyzed Regioselective Cyclization of o‐(Alkynon‐1‐yl)phenols

Synthesis of Flavones by Thallium(III) p‐tosylate‐catalyzed Regioselective Cyclization of o‐(Alkynon‐1‐yl)phenols

Synthetic Approaches to N‐Methoxy‐N‐methylamides

New Perspectives for Fisetin

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