This study presents an innovative metal-free synthesis of 1,2-bis(indolyl)ethenes and benzo[α]carbazoles. The reaction proceeds via an in situ-generated acetal intermediate from vinylene carbonate and HFIP. This intermediate undergoes electrophilic substitution with free-NH-indoles, forming indolyl-3-acetaldehydes. Subsequently, a secondary electrophilic condensation with additional indoles or C2-aryl rings selectively yields (E)-1,2-bis(indolyl)ethenes or benzo[α]carbazoles, depending on the starting materials. Serving as both solvent and reagent, HFIP enables direct C–H functionalization without metallic catalysts. This single-pot methodology offers a streamlined, atom-economical route to complex polycyclic heteroaromatics with broad functional group tolerance. Its mild conditions and simple purification underscore its practical utility for the large-scale construction of diverse indole derivatives.