Single-atom skeletal editing of 2H-indazoles enabled by difluorocarbene

A novel difluorocarbene promoted single-atom skeletal editing of 2H-indazoles is demonstrated herein. Ethyl bromodifluoroacetate was severed as the difluorocarbene source in the current protocol, facilitating the cleavage of the N−N bond via carbon atom insertion. This metal-free ring expansion reaction enables the late-stage diversification of indazole skeletons, assembling a diverse array of functionalized quinazolin-4(3H)-ones in decent yields with excellent functional group compatibility.