CuBr2-Mediated One-Pot Synthesis of Sulfonyl 9-Fluorenylidenes.

In this article, a high-yield method for the synthesis of sulfonyl 9-fluorenylidenes is described, which consists of a one-pot straightforward three-step synthetic route, including (i) CuBr2-mediated α-bromination of o-arylacetophenone, (ii) sequential nucleophilic substitution of the resulting α-bromo o-arylacetophenone with sodium sulfinate (RSO2Na), and (iii) the CuBr2-mediated intramolecular Friedel-Crafts cyclizative dehydration. A plausible mechanism is proposed and discussed. This protocol provides a highly effective regio- and stereoselective annulation via the formation of one carbon-carbon (C-C) bond and one carbon-sulfur (C-S) bond.