Tandem Acid/Pd‐Catalyzed Reductive Rearrangement of Glycol Derivatives

Herein, we describe the acid/Pd‐tandem‐catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen‐based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a Pd(II) or Pd(0) precursor in loadings as low as 0.75 mol % and α,α′‐bis(di‐tert‐butylphosphino)‐o‐xylene as ligand. The reduction step makes use of formic acid as an easy‐to‐handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.