Stereoselective Synthesis of Indoline-Fused Cyclobutanes via Dual Functionalization of Alkynyl Diazo Carboxylates

We report stereoselective synthesis of indoline-fused
cyclobutanes
through dual functionalization of alkynyl diazoacetates. The development
proceeds through Rh-catalyzed insertion of alkynyl carbenes into 2-alkenyl
anilines, followed by a base-promoted alkynoate–allenoate isomerization
and cycloaddition cascade. The protocol expands the synthetic utility
of alkynyl diazoacetates and provides a broad range of indoline-fused
cyclobutanes with excellent yields and stereoselectivity (up to 97%
yield and >20:1 dr). The synthetic applications of densely functionalized
indoline scaffolds are shown toward obtaining useful motifs.