DFT calculations were performed by Gaussian 09 E.01. DLPNO-CCSD(T) 22 single-point energy calculations were performed by ORCA 4.2.1. 23 Pruned integration grids with 99 radial shells and 590 angular points per shell were used in DFT calculations (int=ultrafine). Geometry optimizations of all the minima and transition states were carried out with BMK functional at 298 K in the gas phase and def2-SVP 25 basis set was used for all atoms. The BMK functional performed well in our previous benchmark study of [Rh(CO)2Cl]2 catalyzed [5+2+1] cycloaddition of ene-VCPs and CO, [4+2+1] cycloaddition of ene-ene-allenes and carbon monoxide, and was chosen in the present study as well. Vibrational frequencies were computed at the same level to check whether each optimized structure was an energy minimum or a transition state. Zero-point vibrational energies were obtained through frequency calculations. Solvent effects were considered based on gas-phase-optimized structures using the same basis set and functional. Solvation energies in toluene were evaluated by a self-consistent reaction field employing SMD model. Based on the optimized structures, single-point energy refinements were performed at the DLPNO-CCSD(T)/def2-TZVPP 25 level (def2-TZVPP/C auxiliary basis set) with TightSCF and TightPNO keywords. In this paper, all discussed energies are Gibbs free energies in solution phase (ΔGsol 298 K) unless otherwise specified. We have searched for all possible conformers for all intermediates and transition states, and the discussed ones in this paper are the most stable. The standard state for CO is 5.5 mM 27 and the other species have standard states of 1.0 M. TOC GRAPHIC