posted on 2022-01-28, 02:03authored byNina F.
C. Ritchie, Adam J. Zahara, Sidney M. Wilkerson-Hill
Herein we report the divergent reactivity
of 2,2-dialkyl-3-(E)-alkenyl N-tosylhydrazones
using Pd-catalyzed
cross-coupling conditions, which enable the Z-selective
synthesis of 3-aryl-1,4-dienes and gem-dialkyl vinylcyclopropanes.
We found that the dialkylbiaryl phosphine ligand SPhos was the optimal
ligand for this transformation producing skipped dienes in up to 83%
isolated yield. The ratio of skipped diene to vinylcyclopropane is
dependent on both the structure of the α,α-disubstituted
hydrazones and the aryl halide partner. Using sterically encumbered
aryl bromides provided the trans-cyclopropane products
selectively in up to 69% yield. The reaction is stereospecific and
stereoselective and occurs alongside a competing 1,2-alkenyl group
migration pathway.