Deacylation of Phenyl Ester Substrates Catalyzed by Hydroxamic Acids and Micellar Effects

Abstract

The deacylations of p-nitrophenyl carboxylates possessing acyl chain length, n, from n=2 to n=16 by hydroxamic acids (benzohydroxamic acid, r-phenylbutyrohydioxamic acid, decanehydoxamic acid, sebacohydroxamic acid, and 2-hexyldecanehydroxamic acid) with or without hexadecyltrimethylammonium bromide (CTAB) were performed to investigate the catalytic activities and substrate-selectivity of the acids.Among the nucleophiles employed, 2-hexyldecanehydroxamic acid, which has the hydrophilic moiety (hydroxamic acid) bound to the branching hydrophobic portion, enhanced markedly the deacylation-rate of the esters in the presence of CTAB. Furthermore, in the presence of CTAB, a characteristic micellar catalysis was observed in the deacylation of p-nitrophenyl decanoate having an appropriate acyl chain length (n=10) selectively enhanced by each of hydroxamic acids employed.