2584-79-4

The irradiation at 340 nm of the title compounds having 9-anthryl and pyren-1-yl groups in methanol was found to give the heterolytic C-O bond cleavage products: 1-hydroxy-2-pyridone and aryl-substituted dimethyl ether (which predominate for the reaction of the former title compound) in addition to 2-pyridone, aryl-substituted methanol and aryl-substituted formaldehyde derived from the homolysis of the N-O bond (which mainly occurs in the photolysis of the latter title compound). It was also found that substitution of the methyl group for hydrogen at the 6-position of the pyridone skeleton in 1-(9-anthrylmethyloxy)-2-pyridone decreases the relative composition of the arylsubstituted dimethyl ether to some extent. These substituent effects on the product compositions were explained in terms of stereoelectronic effects on a charge transfer-type interaction between the aromatic and pyridone rings in the singlet excited state. Analyses of the ground-state conformation for the title compounds by MM2 calculations and 1H NMR spectroscopy, as well as of their singlet excited-state behaviour, substantiated the existence of a non-emissive intramolecular exciplex intermediate which plays a key role in inducing the C-O bond heterolysis.

Irradiation of the title compound having a 9-anthryl (1a) or a 1- pyrenyl group (1b) in methanol was found to give the heterolytic C-O bond cleavage products: 1-hydroxy-2-pyridone and arylmethyl methyl ether, (which predominate for the reaction of 1a), along with 2-pyridone, aryl-substituted methanol and aryl aldehyde derived from the homolysis of the N-O bond (that mainly occurs in the photolysis of 1b). Spectroscopic analysis of the ground- state and excited singlet-state behavior of 1 revealed that a non-emissive intramolecular exciplex (whose formation rate is much faster in 1a than in 1b) plays a key role in inducing the C-O bond heterolysis.

Treatment of 9-bromo-10-methyl anthracene 1, in dipolar aprotic solvents, by alkaline phenoxide or alkoxides leads essentially to a mixture of the expected ether, 9-phenoxy (or alkoxy)-10-methyl anthracene 2, normal substitution product (NSP), and of the isomeric ether, 9-phenoxymethyl (or alkoxymethyl)-anthracene 3, tele-substitution product (TSP).It is shown that both ethers must derive from a common unstable intermediate, the 9-bromo-10-methylene-9,10-dihydroanthracene 8, coming from 1 by a prototropic shift and which can undergo both types of substitution.With more hindered phenoxide ions, only the tele-substitution process is observed.

A competition between normal substitution and tele-substitution is observed with 9-bromoanthracenes bearing in the opposite meso position an ethyl, 1b, or a benzyl group 1d.When treated with potassium phenoxide in HMPT these bromides afford mixtures of 9-alkyl-10-phenoxy-anthracenes 2 and 9-α(phenoxyalkyl) anthracenes 3.On the other hand 9-bromo-10 isopropylanthracene 1c is quite unreactive and 9-bromo-10-methoxymethylanthracene 1e leads essentyally to anthraldehyde 7.