Benzopyrans properties

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). 

For thermographic recording materials, thermochromic properties of the spiroindolino- and spirobenzothiazolino-benzopyrans have been utilized. As an example, thermal paper patented by National Cash Register38 can be cited. In this paper, the colored merocyanine form is fixed by reacting with phenols or metallic salts.2... 

Approaches used to the development of LC materials with valuable luminescent properties include the synthesis of rod-like mesogens from fluorescent moieties, e.g. benzopyrans, " and discotic LCs with a fluorescent polyaromatic core. ... 

A series of 3-alkyl- and 3-aryl-7/7-furo[3,2- ]-l-benzopyran-7-ones 78 (linear furocoumarins) was synthesized and evaluated for their photochemical and nonphotochemical crosslink formation with DNA as well as for their spectro-photometric and fluorescent properties, lipophilicity, and ability to photobleach A, A -dimethyl-/)-nitrosoaniline (RNO) after irradiation with UVA light <2002AP187>. The synthesis of the linear furocoumarins (Scheme 10) was a modification of a previously published method in which 7-hydroxy-2//-l-benzopyran-2-ones 76 were converted into / -ketoethers 77 by alkylation with haloketones under phase-transfer catalysis conditions. Base-catalyzed intramolecular condensation and subsequent acidification gave the corresponding 78. A molecular complex between each one of these fluorescent furocoumarins and DNA was observed, but only compounds with a 3-Me or 3-Ph group showed UVA irradiation-induced crosslink formation. 

Bcnzo[/)]furan and derivatives, recent advances in chemistry of, Part 1, occurrence and synthesis, 18, 337 Benzo[c]furans, 26, 135 recent advances in the chemistry of, and related compounds, 73, 1 Benzofuroxans, 10, 1 29, 251 2//-l-Benzopyrans (chrom-3-enes), 18, 159 Bcnzofc] pyrylium salts syntheses, reactions, and physical properties, 50, 157 1,2-and 2,1-Benzothiazines and related compounds, 28, 73... 

Mannhold R, Cruciani G, Weber H et al. (1999) 6-Substituted benzopyrans as potassium channel activators Synthesis, vasodilator properties, and multivariate analysis. J Med Chem 42 981-991... 

J-C. LeDuc, F. Gamier, and R Guglielmetti, Synthesis and properties of azaheterocyclic spiropyrans containing a chromophoric group of the arylazo type on the benzopyran nucleus, Compt. Rend. Acad. Set., Ser. C, 282, 691-694 (1976). 

The photochromic properties of a number of naturally occurring 27/-1-benzopyrans were studied at low temperatures by Kolc and Becker.65 A few examples of this structurally diverse class of compounds are shown in Figure 3.18. 

When the annellated heteroaromatic group is a five-member ring (43, 44), the properties are best described as intermediate between a naphtho and benzopyran. The standard method of synthesis for diaryl naphthopyrans (acid-catalyzed condensation between a diaryl propargyl alcohol and a naphthol, Scheme 8) is reported not to work for heteroaromatic fused phenols. This is true especially in cases where the heteroaromatic phenol contains a (basic) nitrogen. Alternatively, these pyrans can be prepared by the method of Casiraghi69 outlined in Scheme 16. 

Photoresponsive membranes of cellulose-2,4-diacetate incorporating 6-nitro-l, 3, 3 -trimethylspiro-(2H-l-benzopyran-2,2 -indoline) have been prepared and chiroptical and fluorescence properties of optically active co-polymers of acenaphthalene with methyl acrylate/methacrylate have been investigated. Marked optical activity is induced in the aromatic units only for the co-polymer with methyl methacrylate. This difference in behaviour is associated with an overall higher main-chain flexibility and conformational freedom in acrylates compared with methacrylates. Photoisomerization in polyurethanes containing azo-links has been found to be dependent upon the thermal history of the polymer, and photoisomerization of linoleic acid and... 

When rare-earth-metal ions such as Eu and Tb are bound to polyelectrolyte membranes such as poly(sodium acrylate) and poly(sodium ethene-sulphonate) their fluorescence intensities are considerably enhanced this is associated with the formation of asymmetric bonds between the rare-earth ions and the acrylate/S03 groups in the polymers. This was confirmed by the addition of EDTA to the Tb -poly(sodium acrylate) complex which, because of its preferential binding to the polymer, displaced Tb ions and resulted in reduced fluorescence of the latter. Stokes shifts of fluorescent dyes in different polymer systems have been related more to mobility effects in the polymer than polarity,and the fluorescence of hydrolysed aspirin has been found to be affected by the nature of different polymer supports.The luminescence properties of cis-(2,2 -bipyridyl)ruthenium(ii) complexes have been found to be influenced by binding the complex to a polymer matrix,as have the luminescence properties of flavones and l-octadecyl-3,3-dimethyl-6 -nitrospiro(indoline-2,2 -2H-benzopyran). Other studies of interest in-... 

Cloricromsn [inn] is a benzopyran derivative, a NITRIC OXIDE SYNTHASE INHIBITOR, coronary VASODILATOR. PLATELET AGGREGATION INHIBITOR and antischaemic. It has possible ANTIINFLAMMATORY / IMMUNOSUPPRESSANT properties, and has been used to treat arterial vascular disorders where there is a... 

Phosphorescence lifetimes of 2-amino-l-methyl-6-phenylimidazo[4,5-b]pyri-dine and benzo[f]quinoline increase with decreasing temperature in glucose glasses. A series of articles has addressed the properties of the excited triplet state of 4H-l-benzopyrane-4-thione in perfluoroalkane solvents.Delayed S2-S0 fluorescence arises via triplet-triplet annihilation. 

This chapter, far from being exhaustive, is aimed at outlining the properties of the radical ions and of the free radicals derived from photochromic compounds independently of whether or not these paramagnetic species are involved in the photochromic process itself. In particular, it will deal with the EPR of dihydro-and dialkyldipyridyl radical cations (viologens) and of the radical anions of a variety of nitro-substituted spirofmdoline-benzopyrans], spiro[indoline-naphtho-pyrans], and spiro[indoline-naphthoxazines] as well as their triphenylgermyloxy nitroxides and with the triplet spectra observed upon irradiation of 2,2,4,4-tetrachloro-1 -keto-1,4-dihydronaphthalene. 

The specific structural features of SPs affect the photochromic properties of these compounds. Since photophysical and photochemical properties of organic molecules depend essentially on their structure in the excited state, we shall examine the nature of the structural changes in these molecules upon photoexcitation. The nature of such changes, in turn, depends on the type of electronic transition that converts the molecule into a photochemically active state (PCAS). The converstion of SP1-SP4 molecules to a PCAS upon UV irradiation with k > 300 nm is known to be due to electronic transitions of the n-n type in molecules without EA substituents and of the nn -jt 7t type in molecules with EA substituents in the benzopyran moiety.29 These transitions are characterized by intramolecular charge transfer (ICT), mainly from the l orbital of the oxygen atom and the 7t orbital of the C(3)=C(4) bond to the phenyl group and the EA substitutents. 

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