作者:Toshiaki Yoshimura、Masanori Ohkubo、Takayoshi Fujii、Hiroshi Kita、Youko Wakai、Shin Ono、Hiroyuki Morita、Choichiro Shimasaki、Ernst Horn
DOI:10.1246/bcsj.71.1629
日期:1998.7
S-Alkoxy-S,S-diarylthiazynes were prepared by two methods: the alkaline hydrolysis of S,S-diaryl-N-halosulfilimines in aqueous alcohols and the reaction of S,S-diaryl-S-fluorothiazynes with sodium alkoxides. The structure of S,S-diphenyl-S-propoxythiazyne was determined by an X-ray crystallographic analysis, which showed a short SN bond length of 1.441(3) Å. The thermolysis of S-alkoxythiazynes gave elimination products, which were identified as the corresponding carbonyl compounds and N-unsubstituted S,S-diarylsulfilimines. Kinetic experiments for the thermolysis of the S-alkoxy-S,S-diarylthiazynes were carried out. The first-order kinetic behavior, a large kinetic isotope effect (kH/kD = 6.1) using S,S-diphenyl-S-[1,1-2H2]propoxythiazyne, a negative activation entropy (ΔS‡ = −30 J K−1mol−1), and a negative Hammett ρ-value (ρ = −0.35) on the phenyl group were obtained, suggesting that the reaction proceeds via a concerted five-membered cyclic transition state. A deviation from the ideal concerted transition state is discussed in comparison with that for sulfoxides.
通过两种方法制备了 S-烷氧基-S,S-二芳基噻嗪:S,S-二芳基-N-卤代磺酰亚胺在水醇中的碱性水解以及 S,S-二芳基-S-氟噻嗪与烷氧基化钠的反应。通过 X 射线晶体学分析确定了 S,S-二苯基-S-丙氧基噻嗪的结构,其 SN 键长度较短,为 1.441(3) Å。对 S-烷氧基-S,S-二芳基噻嗪的热分解进行了动力学实验。实验结果表明,S,S-二苯基-S-[1,1-2H2]丙氧基噻嗪具有一阶动力学行为、较大的动力学同位素效应(kH/kD = 6.1)、负活化熵(ΔS‡ = -30 J K-1mol-1)以及苯基上的负 Hammett ρ 值(ρ = -0.35),这表明反应是通过一个协同的五元环过渡态进行的。通过与硫氧化物的协同过渡态进行比较,讨论了与理想协同过渡态的偏差。