A General Synthesis of Substituted Fluorenones and Azafluorenones

Article abstract of DOI:10.1021/jo00250a019

Twenty-one variously substituted fluorenones and azafluorenones have been synthesized via photochemical Pschorr cyclizations of 2-diazoniodiaryl ketones as the key ring-forming step.Direct, (bipy)3Ru^II-, or (bipy)3Ru^II/Cu^II-photosensitized conditions were used, depending on the system to be cyclized.Where selectivities were possible in the ring closure, the isomer ratios obtained were in accord with an aryl radical as the reactive intermediate.The precursor aminodiaryl ketones were obtained from the sequence ortho lithiation of an arylpivalamide, reaction withan aryl aldehyde to give a 2-pivalamidodiarylcarbinol, oxidation to give a 2-pivalamidodiaryl ketone, and hydrolysis to give the 2-aminodiaryl ketone.