A Phosphorus(III)‐Mediated (4+1)‐Cycloaddition of 1,2‐Dicarbonyls and Aza‐o‐Quinone Methides to Access 2,3‐Dihydroindoles

Abstract A (4+1)‐cycloaddition is reported between 1,2‐dicarbonyls and aza‐ o ‐quinone methide precursors to access 2,3‐dihydroindoles bearing a tetra‐substituted carbon center. The utilization of dioxyphospholenes as carbene surrogates provided dihydroindoles in 20–90 % yield, wherein the electronic nature of the dioxyphospholene impacts its role in the reaction.