Photochemical Doyle-Kirmse reaction of Diazopyrazolone and Propargyl thioether: Route to Allenes

Abstract

The pyrazolones are biologically active scaffolds with a significant pharmaceutical interest. However, the diazo analogues of the pyrazolones have not been studied in detail in carbene-mediated transformations. The current study aims at a visible-light catalysed Doyle-Kirmse (D-K) reaction using acceptor-acceptor diazopyrazolones (DIPOLs) with propargyl thioethers. This study involves the procedure that allows an efficient [2,3]-sigmatropic rearrangement in mild condition to provide allene-containing compounds in good conversion, which can then be further transformed into a wide range of products that are known to have pleiotropic effects. In contrast to the previous methods, in our method, the use of harsh conditions and halogenated solvents are avoided, which can offer a sustainable path to the synthetically useful heterocycles.