DDQ/FeCl3-mediated tandem oxidative carbon–carbon bond formation for the Synthesis of indole–fluorene hybrid molecules

Abstract

A series of diverse and complex hybrid structures of indole bearing fluorene were obtained in the presence of DDQ with high regioselectivity under mild conditions from biaryl tethered 3-(methylene)indoline in good to excellent yields. The strategy involves tandem allylic Csp³–H oxidation and subsequent intramolecular carbon–carbon bond formation. The yield of the product was dramatically improved in the presence of additives such as FeCl₃ and molecular sieves (4 Å). A possible mechanism is proposed for this tandem process.