Synergistic Effect of Iodine and Neighboring Amine Groups on Thioester Deacylation

Article abstract of DOI:10.1021/ja00352a026

The synergistic effect of a Lewis acid (I2) and an intramolecular Lewis base facilitates the deacylation of thioesters.When iodine is added to aqueous slution of S-3-(dimethylamino)propylthioacetate (I), deacylation is accelerated by a factor of 10³-10⁴.A severafold acceleration is observed for S-2-(2-pyridyl)ethyl thioacetate (II), and no rate enhancement is observed in the reaction of S-n-butyl thioacetate (III).The rate of iodine consumption at invariant pH and thioseter and iodine concentrations is zero order in iodine when III reacts and the first order in iodine when I reacts.Both kinetic orders are observed when II reacts.The effect of pH and iodine concentration on the rates of I and II is explaned by an intramolecular interaction between an iodine-thioester complex and the neighboring amine.The product of the reaction of the unsubstituted thioester III is the disulfide.However, overoxidation is observed in the reactions of I and II, and the sulfonic acids were the isolated products.The product from the oxidation of I has been confirmed to be (CH3)2⁺NH(CH2)3SO3^- (IV) by single-crystal X-ray crystallography.