Reactions of isatoic anhydride as a masked isocyanate with oxygen and nitrogen nucleophiles—kinetics and mechanism
作者:Anthony F. Hegarty、E. Paul Ahern、Leo N. Frost、Con N. Hegarty
DOI:10.1039/p29900001935
日期:——
The hydrolysis of isatoic anhydride 1, its 5-nitro 7; (X = NO2, R = H) and N-methyl derivatives in water at 25 °C occurs mainly via direct HO– attack on the neutral substrate. At high pH where 1 and 7(X = NO2, R = H) are ionized, the o-carboxyphenyl isocyanate 8b is formed in equilibrium with the anion 8a, and this undergoes a competing reaction with HO–(but at a slower rate). Reaction with amines at
水解等酸酐1,其5-硝基7 ; (X = NO 2,R = H)和25°C水中的N-甲基衍生物主要通过直接HO –攻击中性底物而发生。在高pH下,其中1和7(X = NO 2,R = H)被离子化时,ö -carboxyphenyl异氰酸酯8B与阴离子平衡形成8A,这经历与HO一个竞争反应- (但以较慢的速度)。在pH <10时与酸酐羰基(C-4)上的胺反应的特征在于βnuc值为+1.0,但对攻击胺的空间位高度敏感。因此,阴离子8(X = H)中异氰酸酯的反应仅对于笨重的胺才重要。使用5-硝基衍生物(p K a 6.7),即使在非受阻碱的情况下,也可以测量与共轭碱的反应。这些产生的βnuc值为0.31,有力证据表明反应是通过异氰酸酯8b(X = NO 2)发生的。考虑了对于从等油酸酐开始的杂环合成的意义。