Soft Propargylic Deprotonation: Designed Ligand Enables Au-Catalyzed Isomerization of Alkynes to 1,3-Dienes

By functionalizing the privileged
biphenyl-2-ylphosphine with a
basic amino group at the rarely explored 3′ position, the derived
gold­(I) complex possesses orthogonally positioned “push”
and “pull” forces, which enable for the first time soft
propargylic deprotonation and permit the bridging of a difference
of >26 pKa units (in DMSO) between
a propargylic
hydrogen and a protonated tertiary aniline. The application of this
design led to efficient isomerization of alkynes into versatile 1,3-dienes
with synthetically useful scope under mild reaction conditions.