2-Benzopyran-1,3-dione

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... 

Similarly, reaction of 2-dimethylaminomethylene-3-oxoalkanoates or 2-di-methylaminomethylene-1,3-cyclohexanediones with 2-phenyl-5(4/7)-oxazolone 146, generated in situ from hippuric acid, affords 6-substituted 3-(benzoyl-amino)-2-oxo-2//-pyran-5-carboxylates 204 and 3-(benzoylamino)-7,8-dihydro-2//-l-benzopyran-2,5(6//)-diones 206, respectively. These compounds showed strong local anesthetic activity (Scheme 7.62). ... 

Pyrano-fused heterocycles, namely pyrano[3,2-f]quinoline-2,5(6//)-diones, pyrano[3,2-f]benzopyran-2,5(6//)-dione, and pyrano[3,2-f]pyridine-2,5(67T)-diones, have been efficiently prepared by the condensation of 4-hydroxy-2-(l//)-quinolines, 4-hydroxycoumarin, or 4-hydroxy-(17/)-pyridone with a-acetyl-y-butyrolactone or the sodium salt of a-formyl-y-butyro-lactone in the presence of ammonium acetate <1999JHC467>. 

Reaction of 4-hydroxy-3-(3-oxobutyl)-2//-benzopyran-2-one with (V-fluorobis(trifluoromethyl-sulfonyl)amine (1 d) in chloroform/water at 35 °C for five minutes gives 3-fluoro-3-(3-oxobutyl)-2//-benzopyran-2,4(3//)-dione (24 a) in near quantitative yield as a mixture of diastereomers.148 The 3-(3-oxo-l-phenylbutyl) and 3-[l-(4-chlorophenyl)-3-oxobutyl] derivatives 24b and 24c, respectively, are similarly formed.148... 

Other furocoumarins, although they have rather different structures, have very similar names, which gives rise to confusion. Thus, whereas oroselone (8) is 8-isopropenyl-2//-furo[2,3-A][l]benzopyran-2-one12 and oroselol (9) is 8-(l-hydroxy-l-methylethyl)-2 -furo[2,3- ][l]benzopy-ran-2-one, oreoselone (10) is 2-isopropyl-2,3-dihydro-7 -furo[3,2-gr][l]-benzopyran- 3,7- 2 -dione.13... 

Examples of polycyclic compounds with several heterocyclic rings include aflatoxin B (48)153 (2,3,6aa,9aa-tetrahydro-4-methoxycyclo-penta[c]furo[3, 2 4,5]furo[2,3-A][l]benzopyran-l,l 1-dione) which is... 

The formation of 4-hydroxy-3-phenylcoumarin by heating phenol and diethyl phenylmal-onate at high temperature is accompanied by small amounts of the [l]benzopyrano[4,3-c]-[2]benzopyran-6,l 1-dione (365) (78M1485). 

The reaction of 2,2-dimethyl-4,6-dioxo-l,3-dioxane (Meldrum s acid 394) and its analogues with 3-dialkylaminophenols has been used to prepare some fluorescent 7-dialkylamino-4-hydroxycoumarins (Scheme 127) (77M499). The substituted malonic acid (395) or its dehydration product is a possible intermediate, since it is known that diaryl-malonic esters are accessible from phenols and the 1,3-dioxane. 3-Methoxyphenol yields the pyrano[3,2-c]benzopyran-2,5-dione (396) in this reaction, presumably by annelation of another ring on to initially formed 4-hydroxy-7-methoxycoumarin. 

A very low yield of the coumarinoisocoumarin (508) is obtained during the Pechmann synthesis of 4-hydroxy-3-phenylcoumarin (78M1485). Significant amounts of this [2]ben-zopyrano[4,3-c][l]benzopyran-6,ll-dione are formed when the hydroxyphenylcoumarin is heated with either diphenyl carbonate or diethyl phenylmalonate. 

Bromobenzyloxy)pyrimidine-2,4-diones 155 undergo a radical induced cyclization to furnish l//-isochromeno-[4,3-4]pynmidin-2(6//)-ones (Equation 72). In a similar fashion, 4-(2 -bromobenzyloxy)benzopyran-7-ones 156 cyclize to afford l//-isochromeno[4,3-c]chromen-ll(67/)-ones in high yield (Equation 73) <2003T2151>. 

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). 

In a TTN-mediated oxidative rearrangement route to certain linear pyranoisoflavones, the aurones (2-alkylidene-6,7-dihydro-4-methoxy-7,7-dimethyl-5//-furo[3,2- ][l]benzopyran-3(277),5-diones) (45 R1 = R2 = H, OMe) were obtained in low yields (Equation (20)) <89BCJ826,92H(34)505>. A signal at d 6.45 ppm in the H NMR spectrum due to the benzylidene proton was noted as being characteristic of the aurone system. 

HOMOPHTHALIC ACID AND ANHYDRIDE (a-Toluic acid, o-carboxy-, and 2-benzopyran-l,3-dione)... 

Photooxygenation of natural visnagin (87) affords a variety of products including 4,9-dihydro-4,9-epidioxo-4-methoxy-7-methylidenylfuro[3,2-g]-benzopyran-5,6-dione and 9-hydroperoxy-4-methoxy-7-methyl-5H-furo[3,2-g]benzopyran-5-one. ° Similar studies have also been reported on the 4-hydroxyl derivative. 

Knierzinger, A., and Wolfbeis, O.S., Syntheses of fluorescent dyes. Part 9. New 4-hydroxycoumarins, 4-hydroxy-2-quinolones, 27/,57/-pyrano[3,2-( ]benzopyran-2,5-diones and 27/,57/-pyrano[3,2-c]qiiin-oline-2,5-diones, J. Heterocycl. Chem., 17, 225, 1980. 

Chlorosulfonyl isocyanate is uniquely useful for the formation of hy-dantoins from sterically hindered acid- and base-labile amino nitriles, e.g., the synthesis of optically active spirohydantoins such as the biologically active (4S)-2,3-dihydro-6-fluorospiro(4H-1 -benzopyran-4,4 -imidazolidine)-2, 5 -dione.23... 

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