Rate Constants for Anilidyl Radical Cyclization Reactions
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 rateconstants 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。
A Visible‐Light‐Driven Iminyl Radical‐Mediated C−C Single Bond Cleavage/Radical Addition Cascade of Oxime Esters
A room‐temperature, visible‐light‐driven N‐centered iminyl radical‐mediated and redox‐neutral C−C single bond cleavage/radical addition cascade reaction of oxime esters and unsaturated systems has been accomplished. The strategy tolerates a wide range of O‐acyl oximes and unsaturated systems, such as alkenes, silyl enol ethers, alkynes, and isonitrile, enabling highly selective formation of various
作者:Ka-Pan Shing、Yungen Liu、Bei Cao、Xiao-Yong Chang、Tingjie You、Chi-Ming Che
DOI:10.1002/anie.201806059
日期:2018.9.10
selective amination of tertiary, benzylic, allylic, secondary, and primary C−H bonds with up to 95 % yield. 14 out of 17 substrates were cyclized selectively at C4 to give pyrrolidines. The regioselectivity at C4 or C5 could be tuned by modifying the reactivity of the C5–H bond. Mechanistic studies revealed a concerted or a fast re‐bound mechanism for the aminationreaction. The reaction has been applied
Selenium-Catalyzed Regioselective Cyclization of Unsaturated Carboxylic Acids Using Hypervalent Iodine Oxidants
作者:Fateh V. Singh、Thomas Wirth
DOI:10.1021/ol202800k
日期:2011.12.16
A new and convenient selenium-catalyzed regioselective cyclization of γ,δ-unsaturated carboxylicacids to the corresponding 3,6-dihydro-2H-pyran-2-ones is described. The cyclization products have been obtained in good to excellent yields using diphenyl diselenide as a catalyst and [bis(trifluoroacetoxy)iodo]benzene as a stoichiometric oxidant.
Polar substituent and solvent effects on the kinetics of radical reactions with thiols
作者:Christopher Tronche、Felix N. Martinez、John H. Horner、Martin Newcomb、Martin Senn、Bernd Giese
DOI:10.1016/0040-4039(96)01241-5
日期:1996.8
The rates of thiol trapping of radicals depend upon polarsubstituents (Table 1) and solvent effects (Table 2). The rate accelerating effect of water on the reactions of biologically relevant radicals is of special importance.