Saturday, October 27, 2007
Ballroom Posters (Greenville Hyatt Regency Hotel)
775

A Modified Synthesis of Tellurophene and Various Stille Couplings of the Mono- and Distannane Derivatives

Daniel P. Sweat and Chad E. Stephens. Augusta State University, Augusta, GA

Tellurophene, the heaviest member of the chalcogen heterocycles, has been studied less than other heterocycles due to lack of commercial availability and cumbersome or expensive methods of preparation. The only published procedure for the formation of tellurophene on a larger scale involves the use of liquid ammonia and sodium metal, as well as the strict exclusion of oxygen and moisture. Using this general approach, we have developed a modified aqueous synthesis that utilizes NaBH4 instead of sodium and which has given a 48% yield after distillation on a 75 mmol scale. The reaction takes approximately 6 hours to perform, compared to 2-3 days for the liquid ammonia reaction. The other common, small scale synthesis uses 1,4-bis(trimethylsilyl)-1,3-butadiyne which is considerably more expensive than the 1,4-dichloro-2-butyne used in our procedure. From tellurophene, both 2-(tributylstannyl)tellurophene and 2,5-bis(trimethylstannyl)tellurophene were synthesized in 57% and 42% yield, respectively. Various Stille couplings were then attempted until it was found that the best yields were obtained (up to 92% yield) when an aryl iodide was used in the presence of palladium tetrakis, cesium fluoride, copper (I) iodine in DMF. In contrast, standard Stille conditions (tetrakis in 1,4-dioxane) with aryl bromides gave 30% yields at best.