An auto-tandem catalysis with a strong Brønsted base enabled the synthesis of diarylalkanes containing a benzofuran moiety. Potassiumtert-butoxide efficiently catalyzed both the intramolecular cyclization of less acidicortho-alkynylaryl benzyl ethers and the following intermolecular addition of diarylmethanes to styrenes, demonstrating the high potential of the catalysis in organic synthesis.