Benzopyranes

Phenolic oxygen participates in facile oxypalladation. The intramolecular reaction of 2-hydroxychalcone (105) produces the flavone 106[127]. The ben-zofuran 107 is formed from 2-allyIphenol by exo cyclization with Pd(OAc)2, but benzopyran 108 is obtained by endo cyclization with PdChf S], Normal cyclization takes place to form the furan 109 from 2-(l-phenylethenyl)phe-nol[129]. Benzofuran formation by this method has been utilized in the synthesis of aklavinione (110)[130]. 

Related benzopyran derivatives include the compound CDRI-85/287 [130064-18-5]( >9) from the Central Dmg Research Institute (32). Analogues such as the pyrtohdinoethoxyphenyl have also been evaluated (33). An alternative series of basic ethers of 3-(p-halophenyl)-4-arylchrom-3-enes (40, X = F [128040-44-8] Cl, Br), has been synthesized and all found to be selective ligands for AEBS in vitro (34). 

The alkaloid reserpiae [50-55-5] which is isolated from the roots of Kauwoljia serpentina T., contains a gaUate trimethyl ether moiety. Reserpiae is used as an antihypertensive and a tranquilizer. A vinylogue of reserpiae, rescinnamine [24815-24-5] is also an antihypersensitive (75). Methoxsalen [298-81-7] (8-methoxypsoralen 7JT-9-methoxy-furo [3,2- ] [l]benzopyran-7-one) (21), a furocoumatia that occurs ia plants, eg, l eguminosae and Umbelliferae is used ia the treatment of vitiligo, as a suntanning promoter, and as a sunburn protectant. It is also available by synthesis (76). 

Chloro-3-(2-phenyl-4E -l-benzopyran-4-yHdene)ethyHdene)-1-cyclohexen-l-yl)-2-phenyl-1-benzopyryHumperchlorate. 

Coum rinic Acid Compounds. These synthetic phyUoquinone derivatives and congeners have been employed as anticoagulants since the isolation of 3,3 -methylenebis(4-hydroxy-2H-l-benzopyran-2-one) [66-76-2] (bis-4-hydroxycoumarin or dicoumarol) (1) from spoiled sweet clover in 1939. The ingestion of the latter was responsible for widespread and extensive death of bovine animals at that time. The parent compound for the synthesis of many congeners is 4-hydrocoumarin, which is synthesized from methyl salicylate by acetylation and internal cyclization. The basic stmctures of these compounds are shown in Figure 2, and their properties Hsted in Table 6 (see Coumarin). 

Benzofurobenzopyrans, 4, 995-1000 6H-Benzofuro[3,2-c][l]benzopyrans, 6a,l la-dihydro-— see Pterocarpans Benzofurofurans mass spectrometry, 4, 585 Benzofuro[2,3-d]pyridazines synthesis, 4, 985... 

H-l-Benzopyran-2-ones — see Coumarins Benzopyran-4-ones ring atoms... 

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... 

H-I-benzopyrans in, 3, 665 biosynthesis, 3, 877 Mass spectrometry in biosynthesis methodology, 1, 86 heterocyclic compounds reviews, 1, 77... 

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... 

Synthesis ol benzopyran-4-ones (llavones) (rom o-hydroxychalcones or from benzoturan-3-ones... 

Phenyl-4(4H)-ona-5,7-dlhydroxy-1-benzopyran (3) A mixture oi phioroglucino 1 (2 77 g 22 mnx)l) and ethyl benzoylacetate 2 (7 65 g 40 mmol) was heated lo 240 250°C l< I 5 h The cooled mixture was extracted with 5% NaOH and Ihe aqueous solution was extracted with EtaO Acidification afforded a brown product which after sublimation at 250 300°C/0 01 mm and recrystallizalion from EtOH gave 2 2 g of 3 (33 5%) mp 278°C... 

Trioxsalen (2,5,9-trimethyl-7H-furo[3,2-g]benzopyran-7-one) [3902-71-4] M 228.3, m 233-235 , 234.5-235 . Purified by recrystn from CHCI3. If too impure it is fractionally crystd from CHCl3-pet ether (b 30-60°) using Norit and finally crystd from CHCI3 alone to give colourless prisms, m 234.5-235°. It is a photosensitiser so it should be stored in the dark. [UV Kaufmann J Org Chem 26 117 1961-, Baeme et al. J Chem Soc 2976 1949.]... 

Visnagin (4-methoxy-7-methyI-5tf-furo[3,2-g][l]benzopyran-5-one) 142-145 . Crystd from water. 

Xanthotoxin (Methoxalen, 9-methoxyfuro[3,2-g][l]benzopyran-7-one) [298-81-7] M 216.2, m 146-148 , 148 , 148-149 . Purified by recrystn from CgH6-pet ether (b 60-80°) as silky needles, Et0H-Et20 as rhombic prisms or hot H2O as needles. It is soluble in aqueous alkali due to ring opening of a lactone but recyclises upon acidification. It has UV EtOH at 219, 249 and 300nm (log e... 

Nabitan (39) is a cannabis-inspired analgesic whose nitrogen atom was introduced in order to improve water solubility and perhaps to affect the pharmacological profile as well. The phenolic hydroxyl of benzopyran synthon is esterified with 4-(l-piperidino)butyric acid under the influence of dicyclohexyl carbodi mi de. In addition to being hypotensive and... 

Chemical Name [ (3-(2-(Diethylamino)ethy ] -4-methyl-2-oxo-2H-1 -benzopyran-7-yl] oxy) acetic acid ethyl ester hydrochloride... 

Chemical Name 5,5 -[ (2-Hydroxy-1,3-propanediyl)bis-(oxy)l bis[4-oxo4H-1-benzopyran-2<arboxylic acid] disodium salt... 

Chemical Neme 5,7-Dihydroxy-2-(3-hydroxy-4-methoxyphenyl)-4H-1 -benzopyran-4-one-7-rutinoside... 

Chemical Name 4-Hydroxy-a-(4-hydroxy-2-oxo-2H-1-benzopyran-3-yl)-2-oxo-2H-1-benzo-pyran-3-acetic acid ethyl ester... 

Chemical Name 3-methyl-4-oxo-2-phenyl-4H-1-benzopyran-8-carboxylic acid 2-piperidino-ethyl ester hydrochloride... 

Therapeutic Function Dermal pigmentation enhancer Chemical Name 9-methoxy-7H-furo[3,2-g] [1 ] benzopyran-7-one Common Name 8-Methoxypsoralen ammoidin xanthotoxin Structural Formula ... 

Chemical Name N-[7 [[3-0-(aminocarbonyl)-5,5 di-C-methyl-4-0-methyl-a-L-lyxo-pyranosylj oxyj -4-hydroxy-8-methyl-2-oxo-2H-1 -benzopyran-3-yl] -4-hydroxy-3-(3-methyl-2-butenyl)benzamide... 

Chemicel Neme 2-[2,3-Dihydro-3-(4-hydroxy-3-methoxyphenyll-2-(hydroxymethyll-1,4-benzodioxin-6-yl] -2,3-dihydro-3,5,7-trihydroxy-4H-1 -benzopyran-4-one... 

This reaction can also be used for the synthesis of substituted 1-benzoxepins with one modification instead of the 4/T-benzopyran the 2/7-isomer must be used. 2-[Diazo(phosphoryl)meth-yl]-2//-benzopyrans decompose in the presence of ))3-allylpalladium chloride dimer with elimination of nitrogen to give 1-benzoxepins 2.192 In some cases, the reaction takes a different course and gives 2-methylene-2//-benzopyrans 3.192 In this respect, the bicyclic system behaves differently to the monocyclic diazo(pyranyl)methane. The 2-isomers of the latter structure could not be isolated and gave l//-l,2-diazepines.190 The 4//-benzopyrans do not form benzoxepins but undergo an intramolecular [2+1] cycloaddition to 3,4-dihydro-2,3,4-metheno-2//-ben-... 

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