Transition metal-catalyzed alkyne functionalization was investigated for the development of new methods for selective and efficient carbon-carbon bond formations. Taking advantage of the potential of transition metal vinylidene complexes to mediate catalysis (chapter 1), a tandem process that integrates the β-alkylation of metal alkynyls and a turnover of disubstituted metal vinylidenes was developed (chapter 2). Treatment of iodoenynes with Et ₃N and the complex derived from [Rh(COD)Cl]₂ and P(4-F-C ₆H₄)₃ proved feasible for tandem cyclization reactions of alkynes to afford a variety of 5,6-fused ring systems. In these transformations, the rhodium vinylidene species reacted with a range of pendent functional groups such as alkenyl, hydroxyl, and phenyl groups through [2+2] cycloaddition, nucleophilic addition, and 6π-electrocyclization processes, respectively. The new method was successfully applied to the total synthesis of 3-demethoxyerythratidinone (chapter 3). The double cyclization reaction of the iodoenyne allowed access to the erythrina skeleton by the simultaneous generation of both the A and B rings, enabling the concise synthesis of the natural alkaloid. The dichotomy between 1,1-carbometalation and 1,2-carbomatalation in alkyne functionalization was also studied using iminoalkynes (chapter 4). It was demonstrated that the rhodium-catalyzed addition/cyclization reactions of alkynyl imines took place via 1,2-carbometalation rather than 1,1-carbometalation. A wide range of nucleophiles from aryl/alkenylboronic acids to aryl/alkylzinc species participated well in the process to provide allylic cyclic amines as the products.