Thermodynamically Controlled, Dynamic Binding of Diols to a 1,2-BN Cyclohexane Derivative

The reversible covalent binding of diols to an N-Bn 1,2-BN cyclohexane has been studied by (11)B and (1)H NMR spectroscopy and single-crystal X-ray diffraction analysis. The activation barrier for the reversible B-N Lewis acid-base interaction has been measured by variable-temperature NMR with bound (2R,3R)-(-)-2,3-butanediol (T(c) = -40 °C, ΔG(‡) = 11.2 ± 0.2 kcal mol(-1)). Deuterium labeling experiments demonstrate that ligand exchange is reversible and rapid at room temperature, and competitive binding studies establish diol association as a thermodynamically controlled process.