Ruthenium Catalyzed Divergent Reactivity of Acceptor–Acceptor DIPOL With Different Thioether Derivatives: Access to Bench Stable Sulfonium Ylides and Alkoxy Pyrazoles

Unexplored reactivity of acceptor-acceptor type diazo pyrazolones (DIPOLs) has been effectively explored for the synthesis of novel bench-stable sulfonium ylides and alkoxy pyrazoles. Umpolung reactivity of DIPOL with α-arylthio ketones/esters has been successfully exploited under ruthenium catalysis to achieve oxa-[2,3]-sigmatropic rearrangement. Important feature of this protocol is the exploration of divergent reactivity of DIPOL towards different α-arylthio ketones/esters to access stable sulfonium ylides as well as alkoxy pyrazoles. The protocol has demonstrated a wide functional group tolerance, excellent chemo- and regio-selectivity, and efficient rearrangement involving the carbonyl motif. As an application, flow chemistry has been explored by using a coil reactor as well as continuous stir tank reactor for achieving the gram-scale synthesis.