Divergent Reactivity of α,α-Disubstituted Alkenyl Hydrazones: Bench Stable Cyclopropylcarbinyl Equivalents

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 alpha,alpha-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.

Automated summary

In this study, we report the divergent reactivity of 2,2-dialkyl-3-(E)-alkenyl N-tosylhydrazones under Pd-catalyzed cross-coupling conditions, enabling 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, producing skipped dienes with up to 83% isolated yield. The ratio of skipped diene to vinylcyclopropane depends on the structure of the alpha,alpha-disubstituted hydrazones and the aryl halide partner. Using sterically encumbered aryl bromides selectively provided trans-cyclopropane products with yields up to 69%. The reaction is stereospecific and stereoselective and occurs alongside a competing 1,2-alkenyl group migration pathway.