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 PCy3 or catalyzed by R3PO 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.

Automated summary

A domino [2+4]/[2+3] sequential annulation reaction of MBH carbonates with N-unprotected indoles has been developed, providing a straightforward approach for the synthesis of various pyrroloquinoline derivatives with high selectivity.