Birch Reduction of Aromatic Compounds by Inorganic Electride [Ca2N](+center dot)e(-) in an Alcoholic Solvent: An Analogue of Solvated Electrons

Abstract

Birch reduction of aromatic systems by solvated electrons in alkali metal-ammonia solutions is widely recognized as a key reaction that functionalizes highly stable pi-conjugated organic systems. In spite of recent advances in Birch reduction with regard to reducing agent and reaction conditions, there remains an ongoing challenge to develop a simple and efficient Birch reaction under mild conditions. Here, we demonstrate that the inorganic electride [Ca2N](+center dot)e(-) promotes the Birch reduction of polycyclic aromatic hydrocarbons (PAHs) and naphthalene under alcoholic solvent in the vicinity of room temperature as a solid-type analogy to solvated electrons in alkali metal ammonia solutions. The anionic electrons from electride [Ca2N](+center dot)e(-) are transferred to PAHs and naphthalene via alcoholysis in a polar cosolvent medium. It is noteworthy that a high conversion yield to the hydrogenated products is ascribed to the extremely high electron transfer efficiency of 98%. This simple protocol utilizing an inorganic electride offers a direct and practical strategy for the reduction of aromatic compounds and provides an outstanding reducing agent for synthetic chemistry.