Selective Reduction of Carboxylic Acids to Aldehydes

Keywords

chemoselective - reduction - aldehyde synthesis - carboxylic acids

Significance

Carboxylic acids are abundant building blocks. Reduction of carboxylic acids to aldehydes is often achieved through carboxylic acid derivatives (e. g., Weinreb amides). In this work, Fier and co-workers describe a new pyridinium silane reagent 1, that performs derivatization and intramolecular reduction to form a variety of complex aldehydes.

Comment

Reagent 1 is a Mukaiyama reagent–silyl hydride chimera. It is a stable crystalline solid that is readily prepared from the commercial 2-fluoro-3-iodopyridine in two steps. This reagent can chemoselectively reduce carboxylic acids and carboxylic acid salts to aldehydes. No epimerization of the α-position was observed. Esters can be reduced if 2.2 equivalents of LiOH are used (instead of Li₂CO₃).