Reaction Of Chromones Research Articles

Synthesis of Fluoromethylated Chromones and Their Heteroatom Analogues via Sodium Fluoromethanesulfinate-Enabled Direct Fluoromethylation.

An array of biologically interesting tri/difluoromethylated chromones and their heteroatom analogues were conveniently synthesized from the reaction of chromones and their heteroatom analogues with CF3SO2Na or HCF2SO2Na in the presence of tert-butyl hydroperoxide under mild conditions. A mechanistic pathway involving the generation of the electrophilic tri/difluoromethyl radical, followed with the radical substitution of chromones and their heteroatom analogues, was postulated.

Нуклеофильное сопряженное трифторметилирование хромонов и активированных алкенов под действием реагента Рупперта

This review summarizes data on the reactions of chromones and activated alkenes with trimethyl(trifluoromethyl)silane (Ruppert’s reagent), which occures as a nucleophilic 1,4-trifluoromethylation with high regioselectivity and good yields. The most important chemical properties of the formed products are also considered.

ChemInform Abstract: Recent Progress on the Asymmetric Synthesis of Chiral Flavanones

AbstractReview: [30 refs.

ChemInform Abstract: Synthesis of 6‐(2‐Hydroxyaryl)‐2‐pyridones by the Reaction of Chromones with Cyanoacetic, Acetoacetic, and Malonic Acid Amides.

A reaction of chromones with cyanoacetic, acetoacetic, and malonic acid amides in the presence of sodium ethoxide furnished a number of new 3-substituted 6-(2-hydroxyaryl)-2-pyridones in good yields, including those containing a polyfluoroalkyl group at position 4.

Synthesis of 6-(2-hydroxyaryl)-2-pyridones by the reaction of chromones with cyanoacetic, acetoacetic, and malonic acid amides

A reaction of chromones with cyanoacetic, acetoacetic, and malonic acid amides in the presence of sodium ethoxide furnished a number of new 3-substituted 6-(2-hydroxyaryl)-2-pyridones in good yields, including those containing a polyfluoroalkyl group at position 4.

Domino Reactions of 1,3-Bis(silyl enol ethers) with 4-(Trialkylsilyloxy)benzopyrylium Triflates

4-(Silyloxy)benzopyrylium triflates can be readily generated in situ by reaction of chromones with trialkylsilyl-tri­fluoromethanesulfonate. Domino reactions of silyl enol ethers with benzopyrylium triflates - derived from chromones, 3-cyanochromones and 3-formylchromones - allow an efficient synthesis of a variety of carba- and heterocycles.

Spiro[4H‐chromene‐4,5′‐isoxazolines] and Related Compounds: Synthesis and Reactivities.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Domino Reactions of 1,3‐Bis‐silyl Enol Ethers with Benzopyrylium Triflates: Efficient Synthesis of Fluorescent 6H‐Benzo[c]chromen‐6‐ones, Dibenzo[c,d]chromen‐6‐ones, and 2,3‐Dihydro‐1H‐4,6‐dioxachrysen‐5‐ones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Spiro[4H-chromene-4,5′-isoxazolines] and related compounds: Synthesis and reactivities

Reactions of chromones with methyl ketoximes in the presence of lithium diisopropylamide follow the nucleophilic 1,2-addition mechanism to give spiro[4H-chromene-4,5′-isoxazolines] in good yields. The isoxazoline ring in spiro[4H-chromene-4,5′-isoxazolines] undergoes opening under the action of conc. H2SO4, yielding α,β-unsaturated oximes. Their nitrosation and bromination lead to the corresponding spiroisoxazolines, while the Beckmann rearrangement, to α,β-unsaturated amides. The latter are also formed directly from spiro[4H-chromene-4,5′-isoxazolines] under the action of PCl5. N-Substituted acetophenone hydrazones in the presence of lithium diisopropylamide react at the C(4) atom of 2-trifluoromethylchromone, while acetophenone anil under the same conditions, at the C(2) atom.

Domino Reactions of 1,3‐Bis‐Silyl Enol Ethers with Benzopyrylium Triflates: Efficient Synthesis of Fluorescent 6H‐Benzo[c]chromen‐6‐ones, Dibenzo[c,d]chromen‐6‐ones, and 2,3‐Dihydro‐1H‐4,6‐dioxachrysen‐5‐ones

The condensation of 1,3-bis-silyl enol ethers with benzopyrylium triflates, generated in situ by the reaction of chromones with Me3SiOTf, afforded functionalized 2,3-dihydrobenzopyrans; treatment of the latter with NEt3 or BBr3 resulted in a domino retro-Michael-aldol-lactonization reaction and the formation of a variety of 7-hydroxy-6H-benzo[c]chromen-6-ones. The hydroxy group was functionalized by using Suzuki cross-coupling reactions. The methodology reported was applied to the synthesis of the natural product autumnariol and a new fluorescence dye, which exhibits promising optical properties. 2,3-Dihydro-1H-4,6-dioxachrysen-5-ones were prepared by condensation of chromones with 1,3-bis-silyl enol ethers containing a remote chloride group, domino retro-Michael-aldol-lactonization, and an intramolecular Williamson reaction.

Novel Chemical Modifications at the 4‐Position of Chromones. Synthesis and Reactivity of 4H‐Chromene‐4‐spiro‐5′‐isoxazolines and Related Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Novel chemical modifications at the 4-position of chromones. Synthesis and reactivity of 4 H-chromene-4-spiro-5′-isoxazolines and related compounds

Reactions of chromones with dilithiooximes proceed via nucleophilic 1,2-addition to give, on acidification, 4 H-chromene-4-spiro-5′-isoxazoline derivatives in high yields. On treatment with concentrated H 2SO 4 the isoxazoline ring of this novel spiroannulated heterocyclic system opens to give α,β-unsaturated oximes, which undergo nitrosation, bromination, and the Beckmann rearrangement to the corresponding spiroisoxazolines and α,β-unsaturated amides, respectively. The latter can be obtained directly by the Beckmann rearrangement of 4 H-chromene-4-spiro-5′-isoxazolines.

ChemInform Abstract: Synthesis of 3‐(2‐Benzyloxy‐6‐hydroxyphenyl)‐1‐methylpyrazoles by the Reaction of Chromones with Methylhydrazine.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of 3‐(2‐benzyloxy‐6‐hydroxyphenyl)‐1‐methylpyrazoles by the reaction of chromones with methylhydrazine

AbstractThe 3‐(2‐benzyloxy‐6‐hydroxyphenyl)‐5‐(methyl, phenyl or styryl)pyrazoles were prepared from the reaction of 2‐(methyl, phenyl or styryl)chromones with methylhydrazine. The structure of these compounds has been determined by several nmr techniques, and the reaction mechanism is discussed.

ChemInform Abstract: Reaction of Chromones with Hydroxylamine in Anhydrous Methanol.

AbstractThe title reaction is carried out with a view to clarifying mechanistic aspects discussed in previous reports.

Reaction of chromones with hydroxylamine in anhydrous methanol : A novel route for the preparation of chromone oximes

The reaction of 4H-1-benzopyran-4-one (chromone, bar1 ,) and its substituted derivatives with hydroxylamine in aqueous alcohols gives isoxazoles 5 and 10 , as the major products, whereas 1a is transformed mainly into 8a with hydroxylamine hydrochloride in anhydrous methanol, compounds 5a , 9a and 10a can be also isolated, and the formation of 6a and 7a has been detected, as well. Depending on the character of the substituent, substituted chromones 1b-g afforded 7 , 8 or 9 as the isolable major product. Based on the present experiments compound 6 , produced in an acid-catalyzed methanol addition on 1 , is regarded the key intermediate of the formation of chromone oxime

ChemInform Abstract: CHEMISTRY OF HETEROANALOGS OF ISOFLAVONES. 8. REACTION OF BENZOFURAN ANALOGS OF ISOFLAVONES AND THEIR 4‐THIOXO DERIVATIVES WITH HYDROXYLAMINE AND HYDRAZINE

AbstractDie Benzofurylchromone (I) reagieren mit Hydroxylamin unter Öffnung des Pyronringes und erneuter Cyclisierung zu Isoxazolen (II).

Chemistry of heteroanalogs of isoflavones. 8. Reaction of benzofuran analogs of isoflavones and their 4-thioxo derivatives with hydroxylamine and hydrazine

A number of 3-(2-benzofuryl)-6-ethylchromones and their 4-thioxo derivatives were synthesized, and the action of hydroxylamine and hydrazine on them was investigated. Isomeric 3 (5)-(o-hydroxyphenyl) isoxazoles were obtained in the reaction with hydroxylamine. The predominant formation of one or the other isomer depends on the character of the substituents in the 2 and 4 positions of the chromone. The reaction of chromones with hydrazine leads to o-hydroxyphenylpyrazoles. The compounds obtained were characterized by their IR, UV, and PME spectra.