Ability of Boron to Act as a Nucleophile and an Electrophile in Boryl Shift Reactions Unveiled by Electron Density Distribution Analysis.

The behavior of the tetracoordinate boron of -methyliminodiacetic acid (MIDA) boronates as a nucleophile and an electrophile during the 1,2-boryl migration promoted by a Lewis acid and the 1,4-boryl migration promoted by a neighboring atom, respectively, have been investigated using density functional theory and the quantum theory of atoms in molecules. We found that when boron acts as a nucleophile, the electron density of the B-N interaction of the BMIDA moiety maintains the charge concentration over the boron atom, facilitating its transport toward the electron-deficient center. In this process, the BMIDA remains as a tetracoordinate.