Efficient palladium-catalyzed vinylic C–H alkenylation and allenylation of gem-disubstituted ethylenes with N-tosylhydrazones of arylalkyl and diaryl ketones were achieved to access trisubstituted 1,3-dienes and tetrasubstituted allenes, respectively. An aryl to vinyl 1,4-palladium migration/carbene insertion/β-hydride elimination sequence proceeded to switch the chemo- and regioselectivities to give