Formimidoyl group transfer from activated amidines. Part 1. Hydrolysis of 1-(N-t-butylformimidoyl)imidazole and related imidazole-containing formamides
作者:Anne Chandler、Anthony F. Hegarty、Margaret T. McCormack
DOI:10.1039/p29800001318
日期:——
preference to the pH independent pathways. p-Nitrophenylformamide [formed from (7c)] is itself hydrolysed in basic solution so that complex kinetics result. The C-substituted amidines (7e) and (7f) react 104–102-fold more slowly than the corresponding formamidines. Buffer catalysis of the hydrolysis of (7a) by phosphate and amines is complex, the slope of Kobs.versus[buffer] plots being greater at low
在不存在缓冲剂的情况下,在水中于25°下检查了1-(N-叔丁基甲酰亚胺基)咪唑(7a)水解为叔丁基甲酰胺和咪唑的水解。水解的速率是不依赖pH的pH为7-14和在该区域中显示反应发生经由HO -质子化的基片上的攻击(其p ķ一个是5.0;质子化位点,咪唑氮)。使用溶剂同位素效应,氘标记和取代基效应消除了诸如H 2 O攻击中性底物和通过两性离子(15)反应的替代机制。低于pH 6时,由于H 2,观察到酸催化水解O与质子化底物(pH 4–6)和双质子化底物(pH 0–4)反应;在pH 0,吨½水解<10 -2秒。所述Ñ -arylformamidines(7B)和(7c)的反应通过类似酸催化的途径,但新的反应(标识为HO -对脒攻击)发生在碱,优先于不依赖于pH的途径。对-硝基苯基甲酰胺[由(7c)形成]本身在碱性溶液中水解,因此产生复杂的动力学。所述Ç取代脒(7E)和(1408米)反应10 4