Frontispiece: A Simple Iridicycle Catalyst for Efficient Transfer Hydrogenation of N‐Heterocycles in Water

Abstract

Transfer hydrogenation Transfer hydrogenation is a simple safe way for reduction reactions and using water as a solvent has the additional benefit of being “green”. In their Full paper on J. Xiao et al. report that a cyclometalated iridium complex catalyzes the transfer hydrogenation of various nitrogen heterocycles in an aqueous solution of formate under mild conditions. The catalyst shows excellent functional‐group compatibility and high turnover number, with loadings as low as 0.01 mol % being feasible. A mechanistic study of quinoline reduction suggests that the reaction proceeds via both 1,2‐ and 1,4‐addition pathways, with the catalytic turnover limited by hydride transfer.