Simplified Birch reduction skips the ammonia

Abstract

To break compounds’ aromaticity, chemists commonly rely on the 74-year-old Birch reduction, which uses sodium metal and ammonia. However, the components’ moisture-sensitive nature—requiring practitioners to trot out potentially hazardous ammonia tanks to freshly distill the reagent—makes running the reaction a chore. A modified Birch reduction developed in Jie An’s lab at China Agricultural University lets scientists skip the arduous set-up (Org. Lett. 2018, DOI: 10.1021/acs.orglett.8b00891). The researchers’ first experiences with the Birch reduction, attempting to reduce graphite to graphene, resulted in long set-up times and a small, but likely still smelly, ammonia leak, spurring them to try to simplify things. The new method replaces ammonia with the commercial crown ether 15-crown-5, which can be recovered after the reaction. The crown ether takes on ammonia’s role for the most part; it mixes with a bench-stable sodium dispersion to form the solvated electrons that reduce the substrates and give the reaction its