10- -telluraxanthylium

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. 

Methylphenyl)-telluraxanthene3 1.93 g (4 mmol) of 9-(4-methylphenyl)-telluraxanthylium perchlorate are added to a stirred suspension of 0.5 g (13 mmol) of lithium aluminum hydride and 3.0 g (23 mmol) of aluminum trichloride in 50 ml of absolute diethyl ether at 20°, the mixture is heated under reflux for 1 h, cooled, and 50 ml of ethyl acetate are slowly added. The resultant mixture is poured into 100 ml of 20% aqueous sulfuric acid, the organic layer is separated, the aqueous layer is extracted with two 50 ml portions of diethyl ether, and the combined organic phases are dried with anhydrous sodium sulfate, filtered, and the filtrate is evaporated yield 1.23 g (80%) m.p. 163° (from heptane/benzene). 

When telluraxanthylium perchlorates were reduced with zinc dust in tetrahydrofuran at 20°, stable telluraxanthyl radicals were generated that dimerized reversibly upon cooling to - 40°... 

Treatment of 9-(4-methylphenyl)-telluraxanthylium perchlorate with sodium azide in tetrahydrofuran generated 9-azido-9-(4-methylphenyl)-telluraxanthene2. 

Refluxing telluraxanthenes with triphenylcarbenium perchlorate in trifluoroacetic acid produced telluraxanthylium perchlorates3. 

Addition of perchloric acid or triphenylcarbenium perchlorate to solutions of 9-hydroxytelluraxanthenes formed dark blue telluraxanthylium perchlorates in almost quantitative yields3,4. 

Telluraxanthylium Perchlorate1 A solution of 1.55 g (5.2 mmol) of 9-hydroxytelluraxanthcne and 1.9 g (5.5 mmol) triphcnylcarbenium perchlorate in 30 ml of trifluoroacctic acid is heated under reflux for 30 min. The mixture is cooled, 50 ml of absolute diethyl ether are added, and the precipitate is filtered, washed with three 50 ml portions of absolute diethyl ether, and dried in air yield almost quantiative. 

The telluraxanthylium perchlorates are soluble in trifluoroacetic acid. They react with acetic acid, acetone, and nitromethane1. For the reduction of telluraxanthylium perchlorates to telluraxanthenes see p. 833. 

Methylphenyl)-telluraxanthylium perchlorate was reduced by lithium aluminum hydride to 9-(4-methylphenyl)-telluraxanthene. ... 

Methoxyphenyl)-telluraxanthylium Perchlorate 1 ml (70 mmol) of 70% perchloric acid are added dropwise to a stirred solution of 4.16 g (10 mmol) of 9-hydroxy-9-(4-methoxyphenyl)-telluraxanthene in 60 ml of absolute diethyl ether. The precipitate is filtered, washed with absolute diethyl ether, and the black-violet crystals are dried at 20" in air. The substance decomposes explosively when melted in a capillary at 207°. 

Similarly obtained were the following 9-R-telluraxanthylium perchlorates ... 

---