A room-temperature-stable electride and its reactivity: Reductive benzene/pyridine couplings and solvent-free Birch reductions

In this work, we report the synthesis of a room-temperature-stable electride (RoSE) reagent, namely K+(LiHMDS)e− (1) (HMDS: 1,1,1,3,3,3-hexamethyldisilazide), from accessible starting materials (potassium metal and LiHMDS) via mechanochemical ball milling at 20 mmol scale. Despite its amorphous nature, the presence of anionic electrons in 1, key diagnostic criteria for an electride, was confirmed by both experimental and computational studies. Therefore, by definition, 1 is an electride. Utilizing its anionic electrons, electride reagent 1 exhibited a versatile reactivity profile that includes (1) mediation of C–H activation and C–C coupling of benzene and pyridine and (2) mediation of solvent-free Birch reduction. This work proves the concept of facile mechanochemical synthesis of a room-temperature-stable electride, and it introduces electride 1 to the synthetic chemistry community as a versatile reagent. [Display omitted] •Use mechanical forces (mechanochemistry) to enable sustainable chemical synthesis•An unprecedentedly accessible room-temperature stable electride (RoSE)•RoSE-mediated benzene and pyridine C–H activation and C–C coupling•RoSE-mediated solvent-free Birch reduction Minimizing energy consumption, pollution, and the usage of hazardous chemicals in organic synthesis is a grand scientific challenge. A sustainable vision of organic synthesis requires new reagents, the use of no precious metals or solvents, and the ability to perform challenging transformations under facile conditions. Herein, we report a new and accessible approach to a group 1 metal reagent featuring anionic electrons: an electride. Endowed with unique anionic electrons, electrides have great potential in synthetic chemistry, but the prospect is restrained by their inaccessibility and instability. This work provides the first accessible and scalable room-temperature-stable electride (RoSE). Our preliminary reactivity studies unveil the tip of the iceberg regarding the precious-metal-free RoSE’s potential as a reagent, including benzene and pyridine C–H activation and C–C coupling, and the first solvent-free Birch reductions, which unlock a wealth of possibilities in sustainable organic synthesis. Organic synthesis is playing underpinning roles in industries and academic research. But from a sustainability perspective, current organic synthesis protocols are criticized for the usage of petrochemical-derived solvents and precious-metal reagents. Herein, we report an unpreceden