Fig. 4 |. Mechanistic considerations for the role of the o-aminomethyl group.
a, The proposed mechanism for boronate ester formation at pHs between the first and second pKas, based upon kinetics, crystal structures and isotope effects. The red equilibrium arrows show the dominant pathway, involving general acid-catalysed expulsion of an inserted solvent with a general base-catalysed delivery of the guest. b, The possibility of losing the inserted solvent in a single step if the solvent is not highly ionized between the N and B.