Phosphine-Mediated Sequential [2+4]/[2+3] Annulation to Construct Pyrroloquinolines.

A domino [2+4]/[2+3] sequential annulation reaction of MBH carbonates with N-unprotected indoles has been developed to provide various pyrroloquinoline derivatives in ≤94% yield and 20:1 dr. The reaction could be either mediated by stoichiometric PCy 3 or catalyzed by R 3 PO via P III /P V ═O redox cycling in the presence of phenylsilane. This method assembles polycyclic 1,7-fused indoles in one step diastereoselectively.