The [2+2+2+1] cycloaddition mechanism of enediynes and carbon monoxide catalyzed by the [Rh(CO)2Cl]2rhodium dimer has been studied using density functional theory, comparing this multistep process with thetwo-step reaction in the absence of a catalyst. According to our results, the multistep mechanism agrees withthat previously suggested. The great selectivity of this reaction and the influence of the chosen solvent in thisselectivity were also analyzed.