Thermodynamics and Kinetics of the Hydride-Transfer Cycles for 1-Aryl-1,4-dihydronicotinamide and Its 1,2-Dihydroisomer
作者:Xiao-Qing Zhu、Lei Cao、Yang Liu、Yuan Yang、Jin-Yong Lu、Jian-Shuang Wang、Jin-Pei Cheng
DOI:10.1002/chem.200304714
日期:2003.8.18
derivative GPNA(+) may return to the 1,4-dihydropyridine by a hydride transfer cycle; but when the 1,2-dihydropyridine is used as the hydride donor, the formed pyridinium derivative can not return to the 1,2-dihydropyridine by the hydride reverse transfer from SH(-) to GPNA(+). These results clearly show that the hydride-transfer cycle is favorable for the 1,4-dihydronicotinamides, but unfavorable for the
五个1-(对位取代苯基)-1,4-二氢烟酰胺(GPNAH-1,4-H(2))和五个1-(对位取代苯基)-1,2-二氢烟酰胺(GPNAH-1,2-合成H(2)),分别用于模拟NAD(P)H辅酶及其1,2-二氢异构体的还原反应。将1,4-二氢吡啶(GPNAH-1,4-H(2))和1,2-二氢异构体(GPNAH-1,2-H(2))用对三氟甲基亚苄基丙二腈(S)作为氢化物处理时受体,两个反应均得到相同的产物:吡啶一价转移,吡啶鎓衍生物(GPNA(+))和碳负离子SH(-)。对这两个反应的热力学分析表明,从1,2-二氢吡啶的氢化物转移比从相应的1,4-二氢异构体的氢化物转移要好得多,但是动力学检查表明,前一种反应比后一种反应明显慢,这主要是由于前一种反应的负活化熵大得多。用SH(-)处理形成的吡啶鎓衍生物(GPNA(+))时,主要的还原产物是相应的1,4-二氢吡啶以及痕量的1,2-二氢异构体。对氢化