Phenoxy-5,12-pentacenequinone

5-Phenoxy-6,13-pentacenequinone (0.1 g) in nonaqueous benzene was exposed to UV light (313 nm) for 5 h. Benzene (100 ml) was distilled off the exposed solution in vacuum. The residual solution was filtered through a layer of silica gel. 5-Phenoxy-6,13-pentacenequinone was washed out by benzene. The layer of silica gel with 6-phenoxy-5,12-pentacenequinone was washed by acetone, which was evaporated. Yield 0.07 g (70%). It was isomerized into 5-phenoxy-6,13-pentacenequi-none during determination of the melting point. 

Benzoyl chloride (8.6 ml) and 4 drops of concentrated H2S04 were added to the solution of l,6,8-trichlor-3-o-carbomethoxybenzoylpyrene (5.73 g) in nitrobenzene (170 ml) at 100°C. This mixture was heated to 180°C and stirred for 40 min. The cooled solution was filtered and washed by methanol. Yield 4.32 g (80.7%) of l,6,8-trichloro-2,3-phthaloylpyrene mp 339-340°C. This material was used without further purification in the next step. 

This compound (1 g) was added to melted phenol (8 g) with KOH (0.26 g) at 60°C. The mixture was stirred at 165-170°C for 3 h. The cooled solution was diluted by methanol, filtered, and washed by methanol and hot water. Yield 1.07 g (95%) mp 258-260°C. After crystallization from chlorobenzene, orange crystals, were obtained 272-273°C. 

Barachevsky, G. I. Lashkov, and V. A. Tsekhomsky, Photochromism and Its Application, Khimiya, Moscow (1977) (Russ.). 

Gerasimenko and N. T. Poteleshenko, 1-phenoxyanlhraquinone-one of photochromic compounds of new type, Zh. VKhO im. Mendeleeva 16, 105 (1971) (Russ.). 

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Phenoxy-5,13-pentacenequinone (IV) was obtained by the replacement of chlorine atoms with phenoxy groups in 5-chloro-6,13-pentacenequinone in a phenol-phenoxide melt (Scheme 7).57 5-Chloro-6,13-pentacenequinone was synthesized by cyclization of 2-(l-chloro-2-naphthoyl)-3 naphthoic acid, which was prepared by acylation of a-naphthol with anhydrous naphthalene-2,3-dicarboxylic acid and by the subsequent treatment of the resultant 2-(l-oxy-2-naphthoyl)-3 naphthoic acid with phosphorus pentachloride. 

Absorption bands of the initial and photoinduced forms of 6-phenoxy-5,13-pentacenequinone (Figure 7.13) were slightly shifted (by 10 nm) to the red compared with 11 -phenoxy-5,12-naphthacenequinone.57... 

Figure 7.13. Absorption spectra of 5-phenoxy-6,13-pentacenequinone in toluene (C = 1 x 10 4 mol/ liter) before (1) and after (2) UV irradiation.

Chloro-6,13-pentacenequinone (3.12 g) was mixed at 150°C in a mixture of phenol (30 g) and KOH (0.75 g) for 2 h. The cooled mass was processed by 3% solution of KOH and hot water. Yield 3.22 g (83.5%) of 5-phenoxy-6,13-pentace-nequinone. This material was used without further purification in the next step. 

Yu. E. Gerasimenko andN. T. Poteleshenko, Photochromism of peri-aryloxy-p-quinones. 6-Phenoxy-5,13-pentacenequinone, Zh. Org. Khim. 15, 393-396 (1979) (Russ.). 

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