Asymmetric transfer hydrogenation of seven membered tricyclic ketones: N-substituted dibenzo[b,e]azepine-6,11-dione driven by nonclassical CH/O interactions

Abstract

Enantioselective transfer hydrogenation of dibenzo-fused-azepine-diones: N-substituted dibenzo[b,e]azepin-6-11-dione, was achieved by ruthenium catalysis in the presence of formic acid/triethylamine as a mild hydrogen source. Various derivatives of N-substituted dibenzo[b,e]azepin-6-11-dione were hydrogenated to afford a pharmaceutically important chiral skeleton in excellent yields (80 to >99%) and enantioselectivities (43 to >99%). A theoretical study of the stereodetermining transition state revealed that a dibenzo[b,e]azepine-6,11-dione skeleton has a marked effect of CH/π interactions on enantioselection, instead there is evidence of nonclassical CH/O interactions being responsible for the stereochemical outcome.