Catalytic Asymmetric Insertion of Diazoesters into Aryl-CHO Bonds: Highly Enantioselective Construction of Chiral All-Carbon Quaternary Centers

This
paper describes a catalytic enantioselective route to synthesize
functionalized all-carbon quaternary acyclic systems via a boron Lewis
acid-promoted formal C–C insertion of diazoesters into aryl-CHO
bonds. In the presence of chiral (S)-oxazaborolidinium
cation 1d as a catalyst, the reaction proceeded in good
yield (up to 83%) with good regioselectivity (up to 88:12) and excellent
enantioselectivity (up to 99% ee). The synthetic potential of this
method was illustrated by conversion of the products to both α-
and β-amino esters.