Exchange of Chlorine for Iodine

Diorgano tellurium dichlorides in ethanol or methanol, when treated with an excess of aqueous iodide at 0 to 5°, produced diorgano tellurium diiodides. Examples of diorgano tellurium diiodides prepared in this manner are ( R given)  

4-hydroxyphenyP 3,4-dihydroxyphenyP 4-hydroxy-2-methyl-phenyP 2-hydroxy-5-methylphenyP 2-chloro-2-phenylethenyl  

Irgolic Organo Tellurium Compounds with 2 Te—C Bonds or 1 Tc = C Bond 

The following 2,4-dihydroxyphenyl 4-RO-phenyl tellurium diiodides were obtained similarly in quantitative yields  

Treatment of 4-dimethylaminophenyl 4-RO-phenyl tellurium dichlorides with concentrated hydroiodic acid did not produce tellurium diiodides  

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Pyridones or hydroxypyridines can readily be converted to the corresponding halide by a number of different reaction conditions [24], The use of phosphorous trichloride for transformation was demonstrated in the conversion of 72 to chloride 73. The exchange of chlorine for iodine, as in 74, has already been discussed (vide supra). The corresponding bromide could be obtained using phosphorous tribromide or phosphorous pentabromide, as in the conversions of 72 to 75 and 76 to 77. 

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