Reactivity and detailed reaction mechanism of quasi‐tetrahedral o‐azophenylboronic acid

Quasi‐tetrahedral o ‐azophenylboronic acid (azoB‐ROH), which contains the protic solvent ROH, is a key species in the colorimetric sensing of saccharides by o ‐azophenylboronic acid (azoB). In this study, we compared the reactivity of azoB‐ROH with that of trigonal azoB and tetrahedral o ‐azophenylboronate (azoB‐OH − ), and clarified the reaction mechanism of azoB‐ROH with cis ‐1,2‐cyclopentanediol and D‐glucose. Analysis of the kinetics of the reactions of azoB with cis ‐1,2‐cyclopentanediol and D‐glucose in DMSO:water = 1:9 and azoB with cis ‐1,2‐cyclopentanediol in tetrahydrofuran containing a small amount of methanol revealed that there was not much difference in the reactivity of azoB‐H 2 O and azoB‐OH − , although the reactivity of azoB was higher than that of azoB‐MeOH, that is, the reaction mechanism of azoB‐H 2 O was essentially the same as that of azoB‐OH − .