Asymmetric Hydrogenation of Cyclic Imines of Benzoazepines and Benzodiazepines with Chiral, Cationic Ruthenium–Diamine Catalysts

A method for the highly enantioselective hydrogenation of diverse seven‐membered N‐containing heterocycles, including 2,4‐diaryl‐3H‐benzo[b]azepines, racemic 2,2,4‐trisubstituted 2,3‐dihydrobenzo[b][1,4]diazepines, and 4‐substituted 1H‐benzo[b][1,4]diazepin‐2(3H)‐ones by using chiral, cationic ruthenium–diamine catalysts was developed. Reversal of enantioselectivity was observed for all of these substrates simply by changing the achiral counteranion of the catalyst. This method thus provided facile access to both enantiomers of these optically pure seven‐membered heterocycles. The title hydrogenation reaction is achieved in the presence of phosphine‐free, chiral, cationic ruthenium–diamine complexes and provides facile access to various chiral seven‐membered N‐containing heterocycles. A reversal of enantioselectivity is observed simply by changing the achiral counteranion of the catalyst.