Cascade and Effective Syntheses of Functionalized Tellurophenes.

A one-pot and transition-metal-catalyst-free synthetic strategy to construct functionalized tellurophenes has been developed. Substituted 1,1-dibromo-1-en-3-ynes are smoothly converted to tellurophenes with telluride salts in high yield via a series of cascade reactions through reductive debromination, hydrotelluration, nucleophilic cyclization, and aromatization. Close inspection of the results clearly showed that the reactivity of in situ prepared telluride salts are significantly influenced by the polarity of the solvent system and the electronic nature of the substituent on the enyne substrate. This method reports the first direct synthesis of 3-aryltellurophenes in high yields at room temperature. This novel reaction strategy is also found to be a promising synthetic method for multisubstituted tellurophenes and selenophenes.