Selective Reduction of Esters to Access Aldehydes Using Fiddler Crab-Type Boranes.

The partial reduction of esters to aldehydes is a fundamentally important transformation for the synthesis of numerous fine chemicals and consumer goods. However, despite the many efforts, limitations have persisted, such as competing overreduction, low reproducibility, use of exigent reaction conditions and hazardous chemicals. Here, we report a novel catalyst family with a unique steric design which promotes the catalytic partial reduction of esters with unprecedented, near-perfect selectivity and efficiency.