Novel generation of (α-ketovinyl)thioketenes as intermediates through tandem [2,3]/[3,3] sigmatropic rearrangement of alkynyl propargyl sulfoxides

Thermal reaction of alkynyl propargyl sulfoxides 1 afforded novel highly reactive (α-ketovinyl)thioketenes 3. Trapping experiments using a primary or secondary amine, formation of furanophane 4, through head-to-tail type dimerization, as well as direct observation using 1H NMR elucidated the generation pathway of 3 through sequential [2,3]/[3,3] sigmatropic rearrangement.