Asymmetric Hydrogenation of Tetrapyridine‐Type N‐Heteroarenes Using Phosphine‐Free Ruthenium Diamine Catalysts†

Comprehensive Summary Chiral ruthenium‐catalyzed enantioselective hydrogenation of tetrapyridine‐type N ‐heteroarenes was firstly developed. The partial reduction of adjacent tetraheteroaromatic substrates proceeded smoothly in the presence of phosphine‐free chiral cationic ruthenium diamine complexes, affording unprecedented high reactivity, enantioselecitivity and diastereoselectivity (up to 93% yield, >99% ee and 92 : 8 dr). The potential application of chiral tetradentate pyridine‐amine products as chiral ligands has been demonstrated in the Cu‐catalyzed asymmetric Friedel–Crafts alkylation reaction between indoles and nitroalkenes.