pH-Sensitive C–ON Bond Homolysis of Alkoxyamines of Imidazoline Series with Multiple Ionizable Groups As an Approach for Control of Nitroxide Mediated Polymerization
作者:Mariya V. Edeleva、Igor A. Kirilyuk、Irina F. Zhurko、Dmitry A. Parkhomenko、Yuri P. Tsentalovich、Elena G. Bagryanskaya
DOI:10.1021/jo200341m
日期:2011.7.15
mediators to nitroxide mediated polymerization (NMP) by employing nitroxides with basic or acidic groups as controlling agents. Four alkoxyamines, the derivatives of 2-(4-(dimethylamino)-2-ethyl-5,5-dimethyl-2-(pyridin-4-yl)-2,5-dihydro-1H-imidazol-1-oxyl and 2-(2-carboxyethyl)-5,5-diethyl-2,4-dimethyl-2,5-dihydro-1H-imidazol-1-oxyl, have been prepared. The influence of pH on alkoxyamine homolysis rate constants
最近,Benaglia等人提出了可逆加成-断裂链转移(RAFT)聚合反应的pH可转换剂的新概念。(J.化学会会志。2009,131,6914-6915)。在本文中,我们通过使用具有碱性或酸性基团的氮氧化物作为控制剂,将pH值可调节介体的概念扩展到了氮氧化物介导的聚合反应(NMP)。四种烷氧基胺,2-(4-(二甲基氨基)-2-乙基-5,5-二甲基-2-(吡啶-4-基)-2,5-二氢-1 H-咪唑-1-氧基的衍生物和制备了2-(2-羧乙基)-5,5-二乙基-2,4-二甲基-2,5-二氢-1 H-咪唑-1-氧基.pH对烷氧基胺均溶速率常数的影响(k d)并研究了氮氧化物-烷基自由基的重组速率常数(k c)。所有正在研究的烷氧基胺以及母体氮氧化物都具有几个碱性基团,这些基团在pH值变化的情况下会经历连续的质子化。结果表明,在相同温度下,碱性条件下的k d值比酸性溶液中的k d显着高(高达15倍),而碱性溶液中的k