作者:Osama M. Musa、Seung-Yong Choi、John H. Horner、Martin Newcomb
DOI:10.1021/jo9717907
日期:1998.2.1
measured at ambient temperature. Radicals 4a and 4b were employed as radical clocks in indirect kinetic studies to determine rate constants for reaction of secondary alpha-amide radicals with Bu(3)SnH. The calibrated tin hydride trapping reaction was then employed to determine rate constants for cyclization of the 1-(diethylcarbamoyl)-5-hexenyl radical (12). The rate constants for 5-exo cyclizations of secondary
1-(二乙基氨基甲酰基)-6,6-二苯基-5-己烯基(4a),1-(二乙基氨基甲酰基)-7,7-二苯基-6-庚烯基(4b)和1-(二乙基氨基甲酰基)-通过激光闪光光解法由相应的PTOC酯(羧酸和N-羟基吡啶-2-硫酮的酸酐)制得1-甲基-6,6-二苯基-5-己烯基(4c)。在各种温度下测量自由基4a和4b的环化动力学,并在环境温度下测量4c的环化动力学。自由基4a和4b在间接动力学研究中用作自由基钟,以确定仲α-酰胺自由基与Bu(3)SnH反应的速率常数。然后将校准的氢化锡捕获反应用于确定1-(二乙基氨基甲酰基)-5-己烯基(12)环化的速率常数。仲α-酰胺基的5-exo环化的速率常数与其同构烷基自由基类似物的速率常数相似。叔α-酰胺基团4c的5-exo环化和仲α-酰胺基团4b的6-exo环化的速率常数小于类似的烷基和α-酯取代的基团的速率常数效果。仲α-酰胺自由基的氢化锡捕获速率常数类似