Catalytic Asymmetric Arylation of α‑Aryl-α-diazoacetates with Aniline Derivatives

The
asymmetric arylation of diazo compounds with aniline derivatives
cooperatively catalyzed by an achiral dirhodium complex and a chiral
spiro phosphoric acid is reported. The reaction provides a new method
for the facile synthesis of α-diarylacetates, versatile building
blocks with a diaryl tertiary chiral center, in good yields (up to
95%) with high enantioselectivities (up to 97% ee). Preliminary mechanistic
studies suggest that the arylation reaction proceeds via a stepwise
process, in which the enantioselectivity is controlled by a chiral
spiro phosphoric acid-promoted proton shift in a zwitterionic intermediate.
This work represents the first asymmetric intermolecular C­(sp2)–H bond insertion reaction with arenes.