ABSTRACT 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.
Bankar et al. (Wed,) studied this question.