Expeditious Synthesis of Spiroindoline Derivatives via Tandem C(sp)-H and C(sp)-H Bond Functionalization of -Methyl--nitrosoanilines.

Presented herein is a novel synthesis of pharmaceutically privileged spiroindoline derivatives via cascade reactions of -methyl--nitrosoanilines with diazo homophthalimides. A group of mechanistic studies disclosed that the formation of product involves an unusual reaction mode of -methyl--nitrosoaniline featuring an initial C(sp)-H bond activation/alkylation followed by a C(sp)-H bond activation/spiroannulation. To our knowledge, this is the first example in which -methyl--nitrosoaniline acts as a C3N1 synthon to accomplish formal [4+1] spiroannulation with the participation of the -methyl unit rather than the previously reported C2N1 synthon to undergo formal [3+2] annulation without the participation of the -methyl unit. In general, this newly developed synthetic protocol features simple and readily accessible starting materials, valuable products, unique reaction mechanism, high efficiency and atom-economy, excellent compatibility with diverse functional groups, and ready scalability.