Chromene-5-ones

Benzoyldiaryl ethers are cyclized in good-to-excellent yield by treatment with hot sulphuric acid-acetic acid [3027,3029]. A 2-aminopyran ring is formed when a heterocyclic ketone is heated with a cinnamonitrile and piperidine [3095]. Reduced chromen-5-one are also formed in a basic medium when acroleins are heated with 1,3-cyclohexanediones [2763a]. 

J. Kamalraja, D. Muralidharan, P. T. Perumal, Synlett 2012, 23, 2894—2898. An efficient, one-pot regioselective synthesis of highly functionalized chromene-5-ones and pyrano[3,2-c] chromene-5-ones via a tandem Knoevenagel-Michael-cycli-zation sequence. 

M. S. Singh, G. C. Nandi, S. Samai, Green Chem. 2012, 14, 447 55. DABCO-promoted three-component legioselective synthesis of functionalized chromen-5-ones andpyrano[3,2-c] chromen-5-ones via direct annulation of a-oxoketene-lV,5-arylaminoacetals under solvent-free conditions. 

A solution of cyclic 1,3-dicarbonyl compound (1 1.0 mmol)/ 4-hydroxycoumarin (5 1.0 mmol), arylaldehyde (2 1.0 mmol), NMSM (3 1.0 mmol), and piperidine (20 mol%) in etahnol (2 mL) was stirred at room temperature for the appropriate time (2-5 h). On completion of the reaction (as indicated by TLC), the product (4/6) was filtered and washed with etahnol (2 mL) to remove the excess base and other impurities. Pure chromen-5-ones (4)/pyrano[3,2-c] chromen-5-ones (6) were obtained when recrystallized from EtOH. All the products were characterized from spectral (IR, NMR, NMR, MS) and elemental analyses. 

Obtained by slowly adding 3 M sodium hydroxide to a solution of 4,9-dimethoxy-7-methylfuro[3,2-g] chromen-5-one in refluxing dilute ethanol, then the resulting solution was stirred at 70° for 3 h [4288]. 

Chromones (4f -chromen -ones, 4//-l-benzopyran-4-ones) are naturally occurring oxygen-containing heterocycles which perform important biological functions in nature [46]. Many chromone derivatives, including flavones and 2-(trifluoromethyl)... 

H-pyran synthesis from, 3, 759 bis(trimethylsiloxy) in pyrrole synthesis, 4, 333 chromene synthesis from, 3, 750 cycloaddition reactions with isocyanates, azetidin-2-ones from, 7, 261 dihydropyran synthesis from, 3, 771 fuiyl... 

Homofolic acid, 5,11-methenyl-tetrahydro-biological activity, 3, 327 Homofolic acid, tetrahydro-biological activity, 3, 327 Homoisoflavanones occurrence, 3, 722 thermoisomerization, 3, 722 thermolysis, 3, 728 Homolytic reactions heterocyclic compounds reviews, 1, 74 Homophthalic acid isocoumarins synthesis from, 3, 830 synthesis, 3, 830 Homophthalic anhydride isochroman-l-one synthesis from, 3, 860 20a-Homoporphyrin nomenclature, 1, 30 Homopterocarpin isolation, 4, 998 ( )- D- Homotestosterone synthesis, 1, 453 Homer-Emmons reaction chromene synthesis by, 3, 749 Hortiacine isolation, 3, 149 Hortiamine isolation, 3, 149... 

On the other hand, refluxing 9 in formic acid for 5 h afforded the N-formyl derivative 11 in high yield. Acetylation of 9 by refluxing in acetic acid, afforded acetic acid N -(2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-acetyl)-hydrazide 12 in good yield. Compound 13 was also obtained by refluxing 9 with 3-(2-bromoacetyl)-4-hydroxy-2H-chromen-2-one in ethanol. Reaction of compound 9 with phenyl isothiocyanate in ethanol at room temperature gave 4-phenyl-1 - (7-hydroxy-2-oxo-2 H-chromen-4-acetyl- )thiosemicarbazide 14. 

CB2 Selective Classical Cannabinoids Indoles and Indazoles Resorcinol Derivatives Benzo[c]Chromen-6-one Derivatives... 

Benzo[c]chromen-6-one derivatives, such as AM 1710 (372), were found to be CB2 selective agonists [229]. Although these compounds are structurally similar to the THC derivatives, the dimethyl group on 6-position of the... 

Hydroxymethyl-4,8-dimethylfuro[2,3-/z]chromen-2-one was realized in an efficient manner via a Claisen rearrangement of 4-(hydroxybut-2-ynyloxy)-4-methylchromen-2-one as depicted in the following scheme. Other examples with substitution of hydroxyl and with other substituents, such as chloro, amino, acetoxy were also reported <06JHC763>. A new approach for the synthesis of oxygenated benzo[fe]furans was developed via epoxidation and cyclization of 2 -hydroxystilbene <06T4214>. 

Psoralen, or derivatives of 9-methoxy-7H-furo[3,2-g]chromen-7-one tricyclic ring structures, are used as photoreactive groups in crosslinkers, biotinylation compounds, and nucleic acid probes. Psoralens have been used for many years as photochemotherapy agents for treatment of psoriasis and vitiligo (Smith and Barker, 2006). Psoralens react when exposed to UV light... 

The estrogenic properties of isoflav-3-enes are well known and consequently, several derivatives of these chromene heterocycles have been the target of medicinal chemists. Varma and coworkers uncovered a useful enamine-mediated pathway to this class of compounds [142-144], Now the group has discovered a facile and general method for the MW-expedited synthesis of isoflav-3-enes substituted with basic moieties at the 2-position (Scheme 6.42) [145], These promising results are especially appealing in view of the convergent one-pot approach to 2-substituted isoflav-3-enes... 

Spectrofluorimetric Determination of Al3+ Using 3-hydroxy-2-(4-methoxy phenyl)-4H-chromen-4-one as Analytical Reagent. 

The anodic fluorination of 2-phenylthio-chromen-4-one under similar conditions provides 3-monofluoro- and 2,3,3-trifluoro-products (Scheme 20) [85]. 

None of these reactions could establish whether the positive charge is located on oxygen or on a carbonium ion, although the latter possibility seems more likely. Either way, the positive charge is due to the presence of bonded oxygen. One is justified in speaking of basic surface oxides. The evidence in favor of the chromene structure is rather circumstantial, although many phenomena are explained. A more direct proof should be desirable. 

However, all the broad spectrum of products formed via the reaction of salicylic aldehydes with methylene-active nitriles cannot be shown on a one simple scheme. In the presence of ammonium acetate different chromenes 165 and 166 can be isolated, depending on the order of addition of reagents, the amount of catalyst, and temperature (77S871) (Scheme 60). 

Hexahydro-4/f-chromenes are formed from 1,5-dienes in a one-pot process in which a Rh-complex catalyses sequential hydroformylation, carbonyl ene reaction, a second hydroformylation, cyclisation to a lactol and dehydration <99TL7455>. 

Chloro-2-aryl-2//-chromene-3-carbaldehydes, formed from the reaction of flav-4-ones with dimethylformamide (DMF)/POCl3, react with ethyl 3-aminocrotonate under Hantzsch conditions to give ethyl 2-methyl-5-aryl-5H-chromen[3,4-f]pyridine carboxylates in good yields <2001SC2589>. 

Amino acid-modified furocoumarins were prepared by condensation of the T-hydroxysuccinimide ester of 3-(2,3,5-trimethyl-7-oxofuro[3,2-g]chromen-6-yl)propanoic acid 51 with amino acids <2003JPH177>. Ethyl 3-(7-hydroxy-4-methyl-2-oxo-2/7-3-chromenyl)propanoate 49, prepared in 56% yield by Pechmann condensation of resorcinol and diethyl 2-acetylglutarate in the presence of HCl, was condensed with 3-chlorobutan-2-one in the presence of base to give propanoate 50 (Scheme 4). The MacLeod method was then used to fuse a furan ring to the benzopyran-2-one system. Heating 50 with NaOH solution (1 M) readily cyclized it into the corresponding psoralen furocoumarin 51 with simultaneous hydrolysis of the ester. 

Mass spectra of chromene,24 2-alkylchromenes,24-28 and flavenes29 have been studied. The fragmentation is dominated by the loss of one... 

The 19F NMR spectra of several highly fluorinated derivatives of 2//-pyran (81MI22201, 83JCS(P1)1239) and 4/f-pyran <83JCS(P1)1235> have been reported, as have those of some fluorinated 2,2-dimethyl-2//-chromenes (80JHC1377). The structures of some pyran-2-ones derived from the reaction between phenylacetylene and fluorinated allenes have been ascertained with the aid of their 19F spectra (77IZV2517). 

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