Novel One-Step Synthesis of 9H-Fluoren-9-One From Biphenyl Using Montmorillonite Clay.

9H-Fluoren-9-one is used in the production of antimalaria drugs, thermoplastics, and organic light emitting diodes. In this study, we investigate the novel synthesis of 9H-Fluoren-9-one from biphenyl and carbon tetrachloride on the surface of different homoionic montmorillonite clays. This synthesis occurs in one step under relatively mild reaction conditions, i.e., reflux at 70 degrees C. Formation of 9H-Fluoren-9-one was confirmed by GC/MS retention time and mass spectra comparison to a known standard. Yields were dependent upon the ratio of reagents with a maximum yield of 20% occurring at a 6 to 1 molar ratio of Cu²⁺ ion to biphenyl. Analogous reactions were observed for substituted biphenyls. The reaction is likely initiated by clay stabilized biphenyl aromatic radical cation formation, coupling with carbon tetrachloride, and subsequent ring closure. This reaction mechanism is supported by the observation of color changes of the montmorillonite clay, typical of aromatic radical formation on clay surfaces, and the identification of key reaction intermediates.