Stereoselective Cyclopropanation of Arylmethylidenemalononitriles by 2,6-Dimethylquinoline: A Molecular Electron Density Theory Study

The present work explores the highly trans-stereoselective reaction of a pyridinum ylide (PY1) with 2-(4-chlorobenzylidene)malononitrile (4-CBM) in acetonitrile at 50 degrees C, leading to a cyclopropane-1,1- dicarbonitrile derivative (trans-CP2). The energy transformation, selectivities, and mechanistic aspects of the reaction were figured out by molecular electron density theory (MEDT) at the B3LYP/6-31G(d) computational level. All possible reaction paths were explored, and assessment of the relative Gibbs free energies showed that the ring closure process is the rate-determining step. According to the conceptual density functional theory (CDFT) reactivity indices, PY1 and 4-CBM are classified as a strong nucleophilic and a strong electrophilic species, respectively, which rationalizes the highly polar character of the addition of PY1 to 4-CBM. The preferential C1-C2 bond formation over C1-C3 bonding (regioselectivity) could be explained through an analysis of the calculated electrophilic and nucleophilic Parr functions at the reactive sites of the reactants.