Reactions of phosphonamidic acids and phosphonamidothioic acids with alcohols: mechanistic differences revealed by differing responses to steric effects
作者:Martin J. P. Harger、Cherylin Preston
DOI:10.1039/b307206a
日期:——
The formation of RP(X)(OH)OR′
(R = Pri or But, R′
= Me or Pri) from RP(X)(OH)NHBut and R′OH in CDCl3 is insensitive to steric effects when X = S but not when X = O (>103 times slower with R = But, R′
= Pri than with R = Pri, R′
= Me), pointing to a dissociative elimination–addition mechanism (metathiophosphonate intermediate) when X = S but an associative SN2(P) mechanism when X = O.
在 CDCl3 中,当 X = S 时,RP(X)(OH)OR′(R = Pri 或 But,R′ = Me 或 Pri)与 RP(X)(OH)NHBut 和 R′OH 的形成对立体效应不敏感,但当 X = O 时则不然(R = But 时比 R = Pri,R′ = Me 时慢 >103 倍)、R′ = Pri 时比 R = Pri, R′ = Me 时慢 103 倍以上),这表明当 X = S 时,存在离解消除-加成机制(偏硫代磷酸酯中间体),而当 X = O 时,存在缔合 SN2(P) 机制。