Xanthenones

Xanthenone (xanthone) [90-47-1] M 196.2, m 175.6-175.4 . Crystd from EtOH (25mL/g) and dried at 100°. It has also been recrystd from n-hexane three times and sublimed in vacuo. [Saltiel 5 Am Chem Soc 108 2674 7986]. 

Rewcastle GW, Atwell GJ, Baguley BC, Calveley SB, Denny WA. (1989) Potential antitumor agents. 58. Synthesis and structure-activity relationships of substituted xanthenone-4-acetic acids active against the colon 38 tumor in vivo. JMed Chem 32 793-799. 

Xanthene [92-83-1] M 182.2, m 100.5°, b 310-312°/760mm. Crystd from benzene or EtOH. 9-Xanthenone see xanthone. 

Valence tautomerism is responsible for the photochromic transformation exhibited by the xanthenone (143). This phenomenon is a type of dynamic isomerism in which the primary change is a shift in the position of the valence bonds as illustrated in Scheme 16 (68JOC3469). 

N-Ethoxycarbonylpiperazine 2-Trifluoromethyl-9-xanthenone Hydrogen chloride Potassium hydroxide... 

A solution of 13.2 grams of 2-trifluoromethyl-9-xanthenone in tetrahydrofuran is added over 1 hour to 16.0 grams of 3-(4-benzyloxyethyl-l-piperazinyl) propylmagnesium chloride, prepared as above, in tetrahydrofuran while gently... 

The photochemical ring opening of palustric ester (90), an example of a [l,2]-aimulated cyclohexa-diene, has been achieved wherein a 1 1 photostationary state mixture of diene (90) and triene (91) was obtained. Upon heating for 4 h (162 C), the photo-mixture regenerates palustric ester (90). A related interconversion was observed for a series of photochromic cyclohexadienes of the xanthenone, dibenzo-furan and acridone types, exemplified by (92) -> (93). °... 

Zwi, L. J., Baguley, B. C Gavin, J. B., and Wilson, W. R. (1994) Correlation between immune and vascular activities of xanthenone acetic acid antitumor... 

Zwi, L. J. (1992) The mechanism of the anti-tumour action of flavone acetic acid and its xanthenone acetic acid analogs. Thesis, The University of Auckland, New Zealand. 

Phenyl 3-ethoxyacrylate is cyclized when treated with sulphuric acid and sulphur trioxide at 0°C, but electron-withdrawing substituents on the benzene ring inhibit the reaction. Cyclization of a methoxybenzene to a xanthenone is shown in Chapter 68, Section II.2 [2272],... 

Suitably (lydroxylated benzophenones are oxidatively coupled to give xan> thones by manganese dioxide, DDQ or potassium ferricyanide [2151, 2941]. 2 -Halo-2-hydroxybenzophenones, which are capable of forming benzyne intermediates, are converted into xanthenones by potassamide. Some 3 -halo-2-hydroxybenzophenones also yield xanthenones as one of several products [2676]. 

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