Synthesis of 3,3-Spirocyclic 2-Phosphonoindolines via a Dearomative Addition of Phosphonyl Radicals to Indoles.

The diastereoselective synthesis of α-amino phosphonate derivatives embedded in spirocyclic indolines is reported. The present method proceeds via the dearomative addition of phosphonyl radicals at the C2-position of the indole nucleus in oxidative conditions followed by the intramolecular trapping of the resulting carbocation before rearomatization. trans-3,3-Spirocyclic 2-phosphonoindolines were thus obtained.