Benzopyrano benzopyran

H-l-Benzopyran-4-ones — see Chromones 4H-l-Benzopyran-4-ones, 2-phenyl — see Flavones Benzopyranopyrazoles synthesis, S, 317, 341 Benzopyrano[4,3-c]pytazol-4-one synthesis, 3, 712 Benzopyrano[4,3-6]pyridine synthesis, 3, 712 Benzopyrano[4,3-ii]pyrimidine synthesis, 3, 712 Benzopyrans nomenclature, 1, 23 pyrylium salt synthesis from, 3, 873 reactions... 

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). 

Cyclocondensation of 3-formyl-4/f-l-benzopyran-4-ones (147) with 5 in refluxing benzene containing p-toluenesulfonic acid gave 5a,ll-dihydro-17>H-[ 1 ]benzopyrano[2,3-6][ 1,5]benzothiazepin-13-ones (148) in 70-81%... 

Analogously, 6//-[l]benzopyrano[4,3-6][l, 5]benzothiazepin-6-one (151) was obtained by a cyclocondensation reaction using 3-formyl-2//-l-benzopyran-2-one (150) and 5 (Scheme 47) (91M77). 

Dihydro-6//-[l]benzopyrano[3,4-c][l, 5]benzothiazepines (153) were prepared by cyclocondensation of 5 with 2,3-dihydro-3-dimethylami-nomethyl-4//-1 -benzopyran-4-one (152). Compounds 153 were reduced and alkylated to derivatives 154, which demonstrated sedative and muscle-relaxant activities (Scheme 48) (73FRP2150807). 

BENZOPYRANO(3,4-b)FURO(2.3-h) (1)BENZOPYRAN-6(6aH)-OME, 1,2.12,12a-TETRAHYDRO-2-alpha-ISOPROPENYL-8.9-DIMETHOXY-... 

A mixture of 2 ml of morpholine, 3 ml of dimethylformamide and 10 ml of water was heated to 60°C and under stirring the equal molecular quantity of 6-isopropyl-4-oxo-4H-l-benzopyran-3-carbonitrile was added for 5 minutes. The mixture was heated at that temperature for one hour and the resultant precipitate was filtered, rained with water recrystallized from acetic acid and washed with chloroform. By the above procedure was obtained 2-amino-6-isopropyl-4-oxo-4H-l-benzopyran-3-carboxaldehyde melting at 206°-208°C. A mixture of 4 ml ethyl cyanoacetate, 50 ml of ethanol, 5 ml of piperidine and the equal molecular quantity of 2-amino-6-isopropyl-4-oxo-4H-l-benzopyran-3-carboxaldehyde was refluxed for 30 minutes and, after cooling, the crystalline precipitate was filtered and washed with chloroform. By above procedure was obtained ethyl-2-amino-7-isopropyl-l-azaxanthone-3-carboxylate, melting after recrystallization from ethanol at 243°-244°C. A mixture of 10 ml of acetic acid and 10 ml of 55% sulfuric acid the equal molecular quantity and 2-ethyl-amino-7-isopropyl-l-azaxanthone-3-carboxylate was stirred at 130°C for 4 hours and, after water was added, the precipitate was collected by filtration and recrystalllized from dimethylformamide to give the 2-amino-7-(l-methylethyl)-5-oxo-5H-[l]benzopyrano[2,3-b]pyridine-3-carboxylic acid, melting point 300°C. 

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). 

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... 

Chemical Name Benzopyrano(3,4-fc)furo(2,3-/r) (1 )benzopyran-6 (6aH)-one, 1,2,12,12n-tetrahy-dro-2-a-isopropenyl-8,9-dimethoxy Chemical Abstracts Service Registry Number CAS 83-79-4... 

SYNONYMS 1,2,12,12a-tetrahydro-8,9-dimethoxy-2-( 1 -methylethenyl)-[l]benzopyrano[3,4-b]furo[2,3-h][l]benzopyran-6(6aH)-one tubatoxin. 

Chroman-4-ones have been converted into [l]benzopyrano[4,3-ft][l]benzopyrans (26) via either the 3-benzylidene compound or the pyiylium salt <97F13>. 

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