Mutagenic N-acyloxy-N-alkoxyamides 1 react with thiols by an SN2 process at nitrogen with displacement of carboxylate. They react with glutathione 4 in [D6]DMSO/D2O and methyl and ethyl esters of cysteine hydrochloride, 11 and 12, in [D4]methanol but the intermediate N-alkoxy-N-(alkylthio)amides undergo a rapid substitution reaction at sulfur by a second thiol molecule to give hydroxamic esters and disulfides. Arrhenius activation energies and entropies of activation obtained for a series of different N-benzyloxy-N-(4-substitutedbenzoyloxy)benzamides 13–17 were similar to those found for the SN2 reaction of the same series with N-methylaniline. Entropies of activation were strongly negative in keeping with polar separation and attendant solvation in the transition state, and in keeping with this, bimolecular reaction rate constants at 298 K correlated with Hammett σ constants with a positive ρ-value of 1.1. The structure of model N-methoxy-N-(methylthio)acetamide has been computed at the B3LYP/6–31G(d) level and exhibits properties atypical of other anomeric amides with more electronegative atoms at nitrogen. Relative to N,N-bisoxyl substitution, the combination of a sulfur and an oxygen atom at the amide nitrogen results in a relatively small reduction in amide resonance.
致突变的 N-乙酰氧基-N-烷氧基酰胺 1 通过氮的 SN2 过程与硫醇发生反应,同时羧基发生位移。它们在[D6]DMSO/D2O 中与谷胱甘肽 4 反应,在[D4]甲醇中与半胱氨酸盐酸盐的甲酯和乙酯 11 和 12 反应,但中间的 N-烷氧基-N-(烷硫基)酰胺在硫处与第二个硫醇分子迅速发生取代反应,生成羟肟酯和二硫化物。一系列不同的 N-苄氧基-N-(4-取代苯甲酰氧基)苯甲酰胺 13-17 的阿伦尼乌斯活化能和活化熵与同一系列 N-甲基苯胺 SN2 反应的活化能和活化熵相似。活化熵为强负值,这与过渡态中的极性分离和随之而来的溶解有关;与此相一致,298 K 时的双分子反应速率常数与 Hammett σ 常数相关,正 ρ 值为 1.1。模型 N-甲氧基-N-(甲硫基)乙酰胺的结构是在 B3LYP/6-31G(d) 水平上计算得出的,其性质与氮原子电负性较强的其他同分异构体酰胺不同。与 N,N-二氧代相比,在酰胺氮上结合一个硫原子和一个氧原子会导致酰胺共振相对较小的减少。