Generation of allenylthioketene S,S-dioxides through [3,3] sigmatropic rearrangement of alkynyl propargyl sulfones

Thioketene S,S-dioxides 2 were successfully generated through [3,3] sigmatropic rearrangement of alkynyl propargyl sulfones 1 and the formation of 2 was confirmed by trapping experiment using cyclohexene or allyltrimethylsilane affording a [2+2] cycloadduct 5. In situ generated thioketene S,S-dioxides 2 underwent facile conversion into allenynes 3 in moderate yields, via formation and subsequent [1,2] shift of vinylidene carbenes.