A Nuclearity-Dependent Enantiodivergent Epoxide Opening via Enthalpy-Controlled Mononuclear and Entropy-Controlled Dinuclear (Salen)Titanium Catalysis

A nuclearity-dependent enantiodivergent epoxide opening reaction has been developed, in which both antipodes of chiral alcohol products are selectively accessed by mononuclear (salen)Ti-III complex and its self-assembled oxygen-bridged dinuclear counterparts within the same stereogenic ligand scaffold. Kinetic studies based on the Eyring equation revealed an enthalpy-controlled enantio-differentiation mode in mononuclear catalysis, whereas an entropy-controlled one in dinuclear catalysis. DFT calculations outline the origin of the enantiocontrol of the mononuclear catalysis and indicate the actual catalyst species in the dinuclear catalytic system. The mechanistic insights may shed a light on a strategy for stereoswichable asymmetric catalysis utilizing nuclearity-distinct transition-metal complexes.

Automated summary

A nuclearity-dependent enantiodivergent epoxide opening reaction has been developed, utilizing mononuclear and dinuclear catalysts within the same stereogenic ligand scaffold. The kinetic studies reveal an enthalpy-controlled enantio-differentiation mode in mononuclear catalysis and an entropy-controlled mode in dinuclear catalysis. The mechanistic insights provide a strategy for stereoswitchable asymmetric catalysis using nuclearity-distinct transition-metal complexes.