A first atom-economic [2 + 2] cycloaddition/1,6-conjugate addition cascade of yne-allenones with C-nucleophiles including 1,3-dicarbonyls and α,α-dicyanoolefins under base-promoted conditions has been established, enabling the direct construction of C(sp³)–C(sp³) bonds to generate cyclobuta[a]naphthalen-1-ols with generally good yields. These resulting products have a cyclobutene unit that contains both an aryl and alkyl group.