Iridium-Catalyzed Asymmetric Transfer Hydrogenation for Facile Access to Optically Active Dihydrodibenzo-Fused Azepines

The asymmetric transfer hydrogenation of various dibenzo-fused azepines including 5H-dibenzo[b,e][1,4]diazepines, dibenzo[b,f][1,4]thiazepines and 11H-dibenzo[b,e]azepines using chiral iridium diamine catalysts and HCO2H/NEt3 as the hydrogen source has been accomplished. A range of chiral 10,11-dihydro-5H-dibenzo[b,e][1,4]diazepines, 10,11-dihydrodibenzo[b,f][1,4]thiazepine and 6,11-dihydro-5H-dibenzo[b,e]azepines have been prepared in 82-94% yields with 82-99% ee. Diversely substituted substrates are suitable for this transformation, and a number of functional groups are tolerated. Enantiocontrol is achieved via judicious choice of catalyst, additive and hydrogen source. The synthetic potential of this reaction is explored through gram-scale reactions without loss of reactivity and optical purity and further transformations on products.