Telluraxanthylium Salts

Telluraxanthone reacts with halogens to form the re,7e-dihalides that are reduced to telluraxanthone by sodium sulfite.  

9-Oxotelluraxanthene 180 mg of 9-oxotelluraxanthene Tc.r -dichloride are suspended in 10 w/ of diethyl ether, and the suspension is shaken in a separatory funnel with a solution of 240 mg (1.9 mmol) of sodium sulfite and 180 mg (1.3 mmol) of potassium carbonate in 5 ml of water until the suspended solid has dissolved. The organic phase is separated, the aqueous phase is extracted twice with diethyl ether, the organic phases are combined, washed with water, dried with anhydrous magnesium sulfate, filtered, and the solvent evaporated under aspirator vacuum. The residue is recrystallized from benzene/dichloromethane yield 120 mg (82%) m.p. 116°. 

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The telluraxanthylium salts 92 readily add pyridine at position 9 to give salts 112 (89KGS691). The pyridinium cation behaves as a good nucleofugal group prone to substitution by alkoxy groups when salts 112 are treated with alcohols. 

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