We have developed a novel oxidant-free direct cross-coupling reaction of 2,6-lutidine and internal alkynes leading to five-membered carbocyclic compounds mediated by nonmetallocene cationic hafnium alkyl complexes. Mechanistic studies of the coupling reaction showed that the reaction begins with C(sp(3))-H bond activation via sigma-bond metathesis, after which the coordinatively unsaturated hafnium center mediates further insertion, migration, and beta-H elimination reactions to give five-membered carbocycles from readily available substrates.