Relative reactivities of heteroaromatic cations towards reduction by 1,4-dihydronicotinamides
作者:John W. Bunting、Judy L. Bolton
DOI:10.1016/s0040-4020(01)87506-2
日期:1986.1
reported for the equilibration of the 1-methyl-3-nitropyridinium cation with its pseudobase (hydroxide adduct) and for the reduction of this cation by 1-benzyl-1, 4-dihydronicotinamide. The C-2 hydroxide adduct is the kinetically controlled product (pKR+ = 11.6) when this pyridinium cation is mixed with aqueous base, however, this species rearranges to the C-4 adduct as the themodynamically more stable product
动力学数据报道了1-甲基-3-硝基吡啶鎓阳离子与其假碱(氢氧化物加合物)的平衡,以及该阳离子被1-苄基-1,4-二氢烟碱酰胺还原的动力学数据。当该吡啶鎓阳离子与碱水溶液混合时,C-2氢氧化物加合物是动力学控制的产物(pK R + = 11.6),但是,这种物质重新排列成C-4加合物,成为热力学上更稳定的产物(pK R + = 9.42)。 。可以分析此平衡的pH依赖性,得出k OH = 1600 M -1 s -1氢氧根离子攻击该阳离子的C-4。用1-苄基-1,4-二氢烟碱酰胺还原吡啶鎓阳离子似乎仅在C-4处发生,二级速率常数k 2 = 0.72 M -1 s -1和k 2 H / k 2 D = 2.0 in 20%CH 3 CN-80%H 2 O,离子强度1.0,25°C。