Dual Reactivity of Hydroxy- and Methoxy- Substituted <i>o-</i>Quinone Methides in Aqueous Solutions: Hydration versus Tautomerization.
作者:Selvanathan Arumugam、Vladimir V. Popik
DOI:10.1021/jo101613t
日期:2010.11.5
l (4a), respectively. o-Quinone methides 1 and 2 can be quantitatively trapped as Diels−Alder adducts with ethyl vinyl ether or intercepted by good nucleophiles, such as azide ion (kN3(1) = 3.15 × 104 M−1 s−1 and kN3(2) = 3.30 × 104 M−1 s−1). In aqueous solution, o-quinone methide 2 rapidly adds water to regenerate starting material (τH2O(2) = 7.8 ms at 25 °C). This reaction is catalyzed by specific
通过高效(Φ= 0.3)生成4-羟基-6-亚甲基-2,4-环己二烯-1-酮(1)和4-甲氧基-6-亚甲基-2,4-环己二烯-1-酮(2)。分别对2-(羟甲基)苯-1,4-二醇(3a)和2-(羟甲基)-4-甲氧基苯酚(4a)进行光脱水。邻醌甲基化物1和2可以作为Diels-Alder加合物与乙基乙烯基醚定量捕集,或被叠氮化物离子(k N3(1)= 3.15×10 4 M -1 s -1和k N3)截获。(2)= 3.30×10 4 M -1 s -1)。在水溶液中,ö -quinone甲基化物2迅速加水来再生原料(τ ħ 2 Ô(2)= 7.8毫秒,在25℃)。该反应由特定酸催化(ķ ħ +(2)= 8.37×10 3小号-1中号-1)和特定碱基(ķ OH - (2)= 1.08×10 4小号-1中号-1),但没有明显的一般酸/碱催化作用。与之形成鲜明对比,ö -quinone甲基化物1衰减(τ