作者:E. Martinez、M. Newcomb
DOI:10.1021/jo051953o
日期:2006.1.1
5-diphenyl-4-pentenamidyl radicals (3) were produced by 266 nm laser-flash photolysis of the corresponding N-(phenylthio) derivatives, and the rate constants for the cyclizations of these radicals were measured directly. The 5-exo cyclization reactions were fast (kc > 2 × 105 s-1), and radicals 3 generally behaved as electrophilic reactants with a Hammett correlation of ρ = 1.9 for five of the six radicals studied.
通过相应N-(苯硫基)衍生物的266 nm激光快速光解法制得N-芳基-5,5-二苯基-4-戊烯基基团(3),并直接测量这些基团的环化速率常数。5-exo环化反应非常快(k c > 2×10 5 s - 1),对于所研究的六个自由基中的五个,自由基3通常表现为亲电子反应物,其Hammett相关性为ρ= 1.9。但是,对-甲氧基苯基取代的基团3f的环化速度比Hammett分析所预期的要快得多。母体自由基的可变温度研究3a(芳基=苯基)给出Arrhenius函数,log k = 9.2-4.4 / 2.3 RT(kcal / mol)。用于该反应的速率常数p乙基苯基取代anilidyl自由基3B与卜3 SNH在65℃下是ķ Ť = 4×10 5中号- 1个小号- 1。