Sequential Double α-Arylation of N-Allylureas by Asymmetric Deprotonation and N→C Aryl Migration

On lithiation with lithium amides, N-allyl-N'-aryl ureas undergo rearrangement with transfer of the aryl ring from N to the allylic alpha carbon. From the alpha-arylated products, a further aryl transfer under the influence of a chiral lithium amide allows the enantioselective construction of 1,1-diarylallylamine derivatives. Stereoselectivity in these reactions results from the enantioselective formation of a planar chiral allyllithium under kinetic control.