Ruthenium(II)‐catalysis enabled C–H alkenylations of unactivated naphthoquinones for the preparation of A‐ring‐modified naphthoquinoidal compounds with activity against Trypanosoma cruzi, the parasite causing Chagas disease. The present study encompasses C–H alkenylation by weak O‐coordination by means of ruthenium(II) carboxylates. This method provided an efficient and versatile tool towards a diversity‐oriented strategy for the preparation of compounds with a relevant biological profile.