Synthesis of azafluorenones and related compounds using deprotocupration-aroylation followed by intramolecular direct arylation

Abstract

The efficiency of the deprotocupration-aroylation of 2-chloropyridine using lithiocuprates prepared from CuX (X=Cl, Br) and LiTMP (TMP=2,2,6,6- tetramethylpiperidido, 2 equiv) was investigated. CuCl was identified as a more suitable copper source than CuBr for this purpose. Different diaryl ketones bearing a halogen at the 2 position of one of the aryl groups were synthesized in this way from azines and thiophenes. These were then involved in palladium-catalyzed ring closure: substrates underwent expected CH-activation-type arylation to afford fluorenone-type compounds, and were also subjected to cyclization reactions leading to xanthones, notably in the presence of oxygen-containing substituents or reagents. © 2013 The Authors. Published by Elsevier Ltd. All rights reserved.