Pyrano benzopyran-5-ones

This synthesis involves Michael cycloaddition reaction of the readily available 4-hydroxycoumarine 1 with a cyanocrotonitrile 2 in ethanolic piperidine to afforded 2-amino-3-cyano-4-methyl-4H, 5H-pyrano-benzopyran-5-one (3). Treatment of 3 with acetic anhydride for 0.5 h and/or 3 h under reflux afforded N-acetyl and [l]benzopyrano[3/,4/ 5,6]pyrano(2,3-d) pyrimidine-6,8-dione derivatives (4) and (5a), respectively. Also, interaction of 3 with benzoyl chloride or formic acid gave the corresponding pyrimidine derivatives (5b,c) while its treatment with formamide afforded the aminopyrimi-dine derivative (6). 

Pyrano[3,2-c]benzopyran-2,5-diones synthesis, 3, 808 Pyranobenzopyranones crystal structures, 3, 623 Py rano[3,2-c][ 1 ]benzopyran-2-ones synthesis, 3, 797 Pyranobenzothiazoles mass spectra, 3, 615 Pyrano[2,3-y]benzoxazine synthesis, 3, 714... 

The Knoevenagel reaction between o-hydroxyaryl aldehydes and ketones and substituted acetonitriles affords high yields of 3-substituted coumarins in aqueous alkaline media <96H(43)1257>, whilst 4-hydroxycoumarins have been elaborated to pyrano [3,2-c]benzopyran-5-ones by reaction with aromatic aldehydes and malononitiile <96P148>. The imine (10) resulting from the complex reaction of o-hydroxyacetophenone with malononitrile undergoes a 1,5-tautomeric shift in solution <96JCS(P1)1067>. 

The enaminones (342) also react with dichloroketene, forming 3,4-dihydropyranones (80JHC61). Dehydrochlorination with triethylamine gives the substituted pyrano[3,2-c]-[l]benzopyran-2-ones (343 Scheme 105). Yields are notably better when at least one of the substituents on the amine is aromatic. 

When 3-(4-j -tolyloxybut-2-ynyloxy)[l]benzopyran-2-one 1 was heated under reflux in carefully purified chlorobenzene, the exclusive product, formed in 92% yield, was 1 -(p-tolyloxymethyl)pyrano[2,3-c][l]benzopyran-5(3i/)-one 2. The compound 2 was also the exclusive product when either xylene or ethylbenzene was used as solvent. However, when 1 was heated under reflux in chlorobenzene containing a catalytic amount of AIBN, 2 was obtained in 20% yield together with 80% of 2-methyl-l-(p-tolyloxymethyl)furo[2,3-c] [l]benzopyran-4-one 3. The compound 3 was the exclusive product when PEG-600, IV.lV-dimethylaniline, pyridine or ethylbenzene containing a catalytic amount of p-TsOH was used as solvent, the yields being 90,90, 80 and 90% respectively. 

The reactivity of 47/-benzopyran-4-ones in Diels-Alder reactions is well documented <1987T3075>, and recently high asymmetric induction has been achieved in the reaction of 3-alkoxycarbonyl-substituted chromones with chiral auxiliaries and Danishefsky s diene <1991JOC2058>. It should be noted that 3-formylchromones can react as heterodienes in the stereoselective inverse electron Diels-Alder reaction with enol ethers <1994T11755> to provide a route to pyrano[4,3-A][l]benzopyrans a heterocyclic nucleus which occurs naturally in the fungal metabolite fulvic acid <1984CC1565>. The thermal Diels-Alder reaction of 477-pyran-4-one 405 in the presence of an excess of Danishefsky s diene 404 provided cycloadduct 406 (Equation 32) <1996H(43)745>. 

Treatment of 2-amino-4-(4 -chlorophcnyl)-3-cyano-4H,5H-pyrano[3,2-c][l] benzopyran-5-one (22) [54,55] with triethyl orthoformate in acetic an-... 

The value of 4-hydroxycoumarin in synthesis has been discussed <07THC(11)283> and its use in the synthesis of 3,4-disubstituted coumarins has been reported <07JOC7279>. The 3-arylation of 4-hydroxycoumarins, achieved using aryllead triacetates, sets up a substrate for a cascade of reactions which leads to the [2]benzopyrano[4,3-c][l]benzopyran system <07JOC3293> and the EDDA-catalysed reaction of 4-hydroxycoumarin with a,[3-unsaturated arylaldehydes produces pyrano[3,2-c]benzopyran-5-ones <07T10025>. Propargylation and... 

Watanabe, T., Katayama, S., Nakashita, Y., and Yamauchi.M., Rcgio,specific(biogenetic-type) synthesis of 2-methyl-51I-pyrano 3,2-cl[l benzopyran-4-one, the basic skeleton in citromycetin, J. Chem. Soc. Chem. Commun., 761, 1981. 

Bhavsar and his co-workers reported the formation of pyrano[2,3-a] acridin-2-ones, such as 199, from 8-aroyl-7-hydroxy-benzopyran-2-ones,... 

The pyrano[3,2-c]xanthen-7-one exhibits the two absorption bands associated with a heteroatom at a peri position of the benzopyran nucleus. Pyrano[2,3-a]xanthen-12-one 44, in which the fusion of the chromone ring is reversed, shows an intense single band blue-shifted some 14 nm relative to 2,2-diphenyl-2//-naphtho[l,2-6]pyran [Xmax 403, 482 nm (PhMe)]. Both isomers are readily degraded <01HCA117>. It is noteworthy that 44 could not be... 

Good yields of chromans, dihydrocoumarins and their benzologues result from the Au-catalysed cyclisation of terminal sulfonate esters of alkyl aryl ethers (Scheme 9) <04JA13596> and Bi(OTf)3 catalyses the reaction between salicylaldehydes and 2,2-dimethoxypropane which leads to 2,4-dimethoxy-2-methylchromans with one diastereomer being produced in large excess (Scheme 10). Pyrano[2,3-6]benzopyran has been obtained in a similar manner <04TL9369>. 

Suitably 3-substituted chromones take part in cycloaddition reactions. 3-Acyl derivatives react with 1-alkoxyalkenes in an eiu/o-selective fashion to form pyrano[4,3-/ ][l]benzopyran-10-one derivatives from which a range of chromones and chromanones can obtained (94T11755). 

Van Broeck PI, Van Doren PE, et al (1992) Diels-Alder reactions of pyrano[3,4-b]indol-3-ones and a 2-benzopyran-3-one with hetero substituted olefins generation of carbazole and naphthalene derivatives by elimination instead of dehydrogenation. J Chem Soc, Perkin Trans 1 415 19... 

Synthesis of both enantiomers of the pyrano[3,2-c]benzopyran-4-one, neuchromenin, 32 has been accomplished from 6,7-dihydroxychroman-4-one and the enantiomers of ethyl... 

Trihydroxy-3,3-dime thy 1-5, ll-bis 3-methyl-2-butenyf)-3H,7 l-benzofuro[2,3-b]pyrano[2,3-b][l]benzopyran-7-one,... 

Bidwillon B, B-10022 1 -[2,4-Dihydroxy-3-( 3-methy 1-2-buteny 1) phenyl]-3-(8-hydroxy-2,2-dimethy 1-2//-1 -benzopyran-6-yI)-2-propen-1 -one, D-30198 2-(2,4-Dihydroxyphenyl)-8,8-dimethyl-10-(3-methyl-2-butenyl)-8//-pyrano[2,3-rf) chroman-4-one, D-10234... 

FIGURE 11.83 Solid-phase synthesis of psoralen analogs. (From Song, A., Zhang, J., and Lam, K.S., Synthesis and reactions of 7-fluoro-4-methyl-6-nitro-2-oxo-27f-l-benzopyran-3-carboxylic acid a novel scaffold for combinatorial synthesis of coumarins, J. Comb. Chem., 6,112, 2004 Song, A. et al.. Solid-phase synthesis and spectral properties of 2-alkylthio-6//-pyrano[2,3-/ benzimidazole-6-ones a combinatorial approach for 2-aUcylthioimidazo coumarins, J. Comb. Chem., 6, 604, 2004 Song, A. and Lam, K.S., Parallel sohd-phase synthesis of 2-arylamino-6H-pyrano [2,3-f] benzimidazole-6-ones, Tetrahedron, 60, 8605, 2004.)... 

Dihydro- ll-hydroxy-5-methoxy-2,2-dimethyl-2H,8li-benzofuro[3,2-c]pyrano[2,3-f [l]benzopyran-8-one, 9CI [23013-86-7]... 

C14H14O3, DL-4-Methoxy-6-styryl-5,6-dihydro-a-pyrone, 38B, 335 Cl4H14O3, 1,2,3,4,4a,5,8,8a-Octahydro-1,4,5,8-exo,exo-dimethanonaph-thalene-4a,8a-dicarboxylic anhydride, 46B, 320 C1ftH1flOa, cis-2-Hydroxy-2,4-dimethyl-3,4-dihydro-2H,5H-pyrano[3.2-c][1]benzopyran-5-one, 45B, 332... 

Dihydroxyphenyl)-3,3 a,4,5-tetrahydro-4,8-dihydroxy-2 H-pyrano[4,3,2-de]-l-benzopyran-2-one (2,3-cw,3,4-rra 5-Dryopterin) Dryopteris filix-mas Schott C17H14O7 118 181 ... 

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