Unexpected reaction of 1-butyltelluro-4-phenyl-1-buten-3-yne under Rupe reaction conditions

Treatment of 1-butyltelluro-4-phenyl-1-buten-3-yne (3) with an aqueous solution of formic acid results in formation of the unexpected 2-phenyl-3-(4-phenylbut-3-yn-1-enyltelluro)tellurophene 5. Formation of the expected alpha,beta-unsaturated ketone beta-telluro-substituted 4 was not observed by the reaction of 3 under Rupe reaction conditions. The structure of the product obtained was confirmed by X-ray diffraction of the dichlorotelluro derivative 6.