Tellurophenes 1,3-diynes

A modification of this method is known When a sodium telluride solution in ethanol at 30°C is treated with l,4-di(trimethylsilyl)buta-l,3-diyne for 3 h, the result is tellurophene in 84% yield (78CB3745). 

Nucleophilic addition of sodium telluride to 1,3-diynes serves as a general method for the synthesis of 2- and 2,5-disubstituted tellurophenes (Equation 18) <1966AG940, 1968BRP1107698, 1972ADC777, 1972J(P1)199,... 

A preparatively convenient method for the synthesis of tellurophene is based on the use of stable and accessible l,4-bis-(trimethylsilyl)buta-l,3-diyne (Scheme 18) <1972JOMC66, 1978CB3745>. Purification of the tellurophene product can be achieved through an oxidation-reduction (Br2/Na2S03) cycle. The yields of pure tellurophene are in the range 53-59%. 

Addition of hydrogen selenide and hydrogen telluride to diynes has been used for the synthesis of selenophenes and tellurophenes. 

Furan also undergoes a primary [4+2] cycloaddition with 3, but this is followed by a [2+1] addition of 2 to the newly formed double bond to furnish the isolated tricyclic compound 5. Thiophene behaves differently its reaction with 3 furnishes the disilathiirane 6 as a formal sulfur-abstraction product [3]. This strongly divergent behavior of five-membered ring systems prompted us to investigate the photolyses of 1 also in the presence of a selenophene, a tellurophene, and a pyrrole. We report here on the photolysis of 1 in the presence of these cyclic dienes as well as similar reactions with acyclic diynes. 

A soln. of Na-telluride in methanol treated at 20° with the equimolar amount of the diyne, and the product isolated when the violet color of the telluride has disappeared 2,5-bis(dimethylhydroxymelhyl) tellurophene. Y almost 100%. 

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