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An unprecedented intramolecular acylation of unactivated pyridines via multiple C(sp/sp)-H functionalizations of a methyl, hydroxymethyl, or aldehyde group has been developed providing a general access to all four azafluorenones. The application of this protocol is further demonstrated to the synthesis of azafluorenone related fused nitrogen heterocycles and fluorenones. In addition, design and synthesis of a novel fluorene based organic emitter for potential use in organic light emitting devices (OLEDs) is also reported.

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A transition-metal-free, t-BuOOH mediated intramolecular carbonylation of arenes in 2-aryl-3-picolines via oxidative C-H functionalizations of the methyl group has been developed, providing an expedient synthesis of 4-azafluorenones. Distinct from the current literature wherein methylarenes have been used as acylating agents, 2-aryl-3-picolines in this study are transformed into aldehydes, which give 4-azafluorenones upon rapid intramolecular acylation. The study demonstrates the first example of intramolecular carbonylation of arenes utilizing a methyl group as latent carbonyl functionality.

Fluorenones are important constituents in material, medical and chemical sciences with potential applications in various domains. The key factors responsible for the diverse usage of fluorenones in material sciences are their intriguing and tunable photo, as well as physico‐chemical properties. Besides this, the presence of conjugated poly‐(en)ynes in the fluorenones makes them molecules of interest in material sciences. Fluorenones show various biological activities like antibiotics, anticancer, antiviral, and neuromodulatory, etc. Organic chemists are developing various protocols for the synthesis of fluorenones. Despite several protocols developed for their synthesis since 1931, there is no review covering their entire synthetic protocols. This review includes several classical and novel synthetic approaches for the synthesis of fluorenones. Furthermore, we delineated the mechanism by which they have been synthesized.