Unconventional diastereoselectivity and mechanism of Cp*Co(<scp>iii</scp>)-catalyzed C–H functionalization of asymmetric dienes: a DFT perspective

The Cp*Co(III)-catalyzed C-H functionalization of 2-methyl-substituted dienes and <i>N</i>-cyanosuccinimides has been systematically investigated using DFT calculations. Key findings reveal that the unconventional diastereoselectivity for the diene <i>si</i>-face insertion over the <i>re</i>-face alternative originates from the additional CH…π interaction occurring in the <i>si</i>-face pathway. Subsequently, σ-rotation/coordination isomerization accelerates the ligand-to-ligand H-transfer (LLHT) process. Furthermore, an unprecedented "succinimide O-coordination → 3,3-rearrangement → LLHT" mechanism was proposed, in which the succinimide carbonyl group not only relieves the key ∠Co-N²-C⁵ distortion to facilitate 3,3-rearrangement but also ensures a straight N¹⋯H orbital interaction to promote LLHT. We anticipate that these insights will inspire the development of related C-H functionalization protocols.