Mechanistic study on the reaction of boronic acids with H-resorcinol

Kinetics for the reaction of m-nitrophenyl- (m-NO2Ph-), phenyl- (Ph-), meth yl(Me-), and n-butyl- (n-Bu-) boronic acids with H-resorcinol has been stud ied at various temperatures and pressures. The pseudo first-order rate cons tant (k(obs)) exhibited saturation in the plot of k(obs) against the total boronic acid concentration (C-B) for the reactions of m-NO2PhB(OH)(2) and P hB(OH)(2), while the plot was linear for the reactions of MeB(OH)(2) and n- BuB(OH)(2), which leads to the following equations, respectively: k(obs) = k*KCB/(l + KCB) and k(obs) = k*KCB = k(f)C(B). It was experimentally shown that the reaction of boronic acids with H-resorcinol proceeds with rate det ermining second chelate-ring closure. (C) 1999 Elsevier Science S.A. All ri ghts reserved.