Access to Conjugated Dienes and Cyclic Allenes via a Diazo-Dithiane Rearrangement Cascade

A transition-metal-free, base-promoted cascade between alkynyl-1,3-dithianes and α-diazodiesters has been developed. The reaction proceeds through an anion relay chemistry (ARC) featuring a selective 1,3-sulfur rearrangement, enabling divergent access to eight-membered sulfur-containing conjugated dienes and cyclic allenes in a one-pot fashion. This transformation unveils new diazo reactivity beyond classical carbene pathways and highlights the synthetic utility of sulfur-based anionic processes.