Difluorocarbene-Enabled Synthesis of 3-Alkenyl-2-oxindoles from ortho -Aminophenylacetylenes.

Herein, we report a transition-metal-free [4 + 1] cyclization pathway from difluorocarbene and ortho -amino aryl alkynone, rendering an effective and universal strategy for the construction of 3-alkenyl-2-oxindoles. Our strategy starts from cheap and accessible ortho -amino aryl alkynone instead of the direct indole skeleton; moreover, in situ generated difluorocarbene from commercially available halogenated difluoroalkylative reagents enables the cleavage of a C-N bond and formation of new C-N bonds and C-C bonds.