Expeditious Synthesis of Spiroindoline Derivatives via Tandem C(sp²)–H and C(sp³)–H Bond Functionalization of N-Methyl-N-nitrosoanilines

Abstract

Presented herein is a novel synthesis of pharmaceutically privileged spiroindoline derivatives via cascade reactions of N-methyl-N-nitrosoanilines with diazo homophthalimides. A group of mechanistic studies disclosed that the formation of product involves an unusual reaction mode of N-methyl-N-nitrosoaniline featuring an initial C(sp 2 )−H bond activation/alkylation followed by a C(sp 3 )−H bond activation/spiroannulation. To our knowledge, this is the first example in which N-methyl-N-nitrosoaniline acts as a C3N1 synthon to accomplish formal [4+1] spiroannulation with the participation of the N-methyl unit rather than the previously reported C2N1 synthon to undergo formal [3+2] annulation without the participation of the N-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.

Synthesis of Indenone-Fused Pyran Derivatives from Aryl Enaminones and Cyclopropenones through Unsymmetrical Relay C–H Bond Activation and Double C–C/C–O Bond Formation

“…Inspired by those elegant pioneering studies and as a continuation of our own enthusiasm for CHA reactions, , we have designed and explored the reaction of aryl enaminones with cyclopropenones. From this study, an unprecedented reaction leading to otherwise difficult-to-obtain indenone-fused pyran derivatives was disclosed (Scheme g).…”