Ligand-Controlled Catalytic Landscapes in Copper-Catalyzed Boraformylation of Allenes: Computational Insights

Abstract Copper-catalyzed boraformylation of allenes provides access to β-boryl-β,γ-unsaturated aldehydes, but its efficiency is highly dependent on the supporting ligand. In this work, we present a comparative computational investigation of three representative ligand classes─triphenylphosphine (PPh3), an N-heterocyclic carbene (IPr), and a bidentate phosphine (DTB-dppbz)─with the aim of clarifying how ligand identity shapes catalytic performance. Density functional theory calculations were used to map the full reaction profiles, including all key intermediates and transition states along the catalytic cycle. The three catalysts follow the same general sequence, involving allene insertion into a borylcopper species, addition of the resulting β-boryl allylcopper intermediate to methyl formate, β-elimination, and σ-bond metathesis with B2(pin)2 to regenerate the catalyst. Energetic span analysis reveals that the PPh3- and IPr-supported cycles are both controlled by the TS1/IM7 pair, but with markedly different spans of 33.0 and 18.7 kcal mol–1, respectively. The large span obtained for PPh3 arises mainly from the pronounced stabilization of the late-cycle IM7 intermediate, rather than from an intrinsically inaccessible insertion transition state. In contrast, DTB-dppbz exhibits two nearly identical energetic spans of 10.6 and 10.5 kcal mol–1, associated with TS3/IM4 and TS1/CAT, respectively, consistent with distributed turnover control. ETS-EDA shows that IPr has the most destabilizing interaction balance in TS1, whereas DTB-dppbz reduces Pauli repulsion and enhances dispersion stabilization in TS3. These results suggest that, within the present computational model, the higher experimental performance of DTB-dppbz can be associated with a more balanced catalytic landscape, combining accessible turnover-relevant transition states with reduced stabilization of late-cycle intermediates.