Ruthenium Catalyzed Tunable Reactivity of Acceptor-Acceptor DIPOL with Different Thioether Derivatives: Access to Bench Stable Sulfonium Ylides and Alkoxy Pyrazoles

Unexplored reactivity of acceptor-acceptor kind of diazo pyrazolones (DIPOLs) has been effectively explored for the synthe-sis of novel bench stable sulfonium ylides and alkoxy pyrazoles. Umpolung reactivity of DIPOL with α-thioesters/ketones has been successfully tapped under ruthenium catalysis to achieve oxa-[2,3]-sigmatropic rearrangement. Important feature of this protocol is the exploration of tunable reactivity of DIPOL towards different thioethers 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 coil reactor as well continuous stir tank reactor for achieving the gram scale synthesis.