Electron flow along the carbonyl insertion into the aminal C-N bond of 1e from The synthesis of N,1,4-tri(alkoxy-hydroxybenzyl)-1,4-diazepane-amines: Investigations on reaction characteristics and mechanism

Electron flow along the carbonyl insertion into the aminal C-N bond of 1e, proceeding via TS 2.1 and TS 2.2. The reaction is initiated by a hydrogen transfer between 1e and the carbonyl-oxygen of the attacking alkoxy-salicylaldehyde, facilitating the nucleophilic attack of the aminal nitrogen. The left panel displays plain geometries, while the right panel also includes intrinsic bond orbitals (IBOs). Following the evolution of the color-coded IBOs along the carbonyl insertion allows to derive the electron flow in terms of curly arrow notation.