Transition metal-free rongalite-mediated geminal C(sp3)-H functionalization of fluorenes.

A transition-metal-free rongalite-mediated strategy has been developed for the geminal difunctionalization of fluorene derivatives, enabling the efficient synthesis of (9-methyl-9H-fluoren-9-yl)methanol derivatives. In this transformation, rongalite plays a unique triple role: acting as a dual C1 synthon source and as a hydride-free reducing agent. The reaction proceeds via in situ generation of reactive intermediates derived from rongalite, which undergo selective nucleophilic addition at the benzylic sp3 carbon of the fluorene framework. This protocol exhibits broad substrate scope, tolerating a wide range of electron-donating and electron-withdrawing substituents on fluorenes. Operational simplicity, metal-free conditions, and gram-scale applicability further highlight the synthetic utility of this method.