Silicon Catalyzed C-O Bond Ring Closing Metathesis of Polyethers.

The Lewis superacid bis(perchlorocatecholato)silane catalyzes C-O bond metathesis of alkyl ethers with an efficiency outperforming all earlier reported systems. Chemoselective ring contractions of macrocyclic crown ethers enable substrate-specific transformations, and an unprecedented ring-closing metathesis of polyethylene glycols allows polymer-selective degradation. Quantum chemical computations scrutinize a high Lewis acidity paired with a simultaneous low propensity for polydentate substrate binding as critical for successful catalysis. Based on these mechanistic insights, a second-generation class of silicon Lewis superacid with enhanced efficacy is identified and demonstrated.