Aminoketone enolisation: influence of increasing chain length on intramolecular catalysis
作者:Brain G. Cox、Paolo De Maria、Lorenza Guerzoni
DOI:10.1039/p29880000163
日期:——
measured by their rates of halogenation. For both series of aminoketones two important factors are responsible for a high reactivity relative to acetophenone: the positive charge on the protonated (and N-methylated) derivatives, which has a strong influence in the α-(n= 1) and β-(n= 2) position, and intramolecular general base catalysis by the neutral amino group, which has a maximum effect for the δ-(n=
动力学结果报道了链长[PhCO(CH 2)n [图中省略] H 2 ],X = CH 2或O;的哌啶子基和吗啉代苯酮的电离速率。n = 2–5]在缓冲液和稀氢氧化物溶液中,通过其卤化速率进行测量。对于这两个系列的氨基酮,相对于苯乙酮而言,有两个重要的因素导致较高的反应性:质子化(和N-甲基化)衍生物上的正电荷,其对α-(n = 1)和β-(n = 2)位置,以及中性氨基对分子内一般碱的催化作用,这对δ-(n= 4)导数。酸性更高的质子化吗啉代酮的结果与相应的哌啶酮几乎相同,并且没有分子内一般酸催化的迹象。对于分子内一般碱催化的反应,较低的速率常数反映了吗啉代基团的碱性降低。